New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Final rule.

SUMMARY:

This action finalizes amendments to the New Source Performance Standards (NSPS) that apply to the Synthetic Organic Chemical Manufacturing Industry (SOCMI) and amendments to the National Emission Standards for Hazardous Air Pollutants (NESHAP) that apply to the SOCMI (more commonly referred to as the Hazardous Organic NESHAP or HON) and Group I and II Polymers and Resins (P&R I and P&R II, respectively) Industries. The EPA is finalizing decisions resulting from the Agency's technology review of the HON and the P&R I and P&R II NESHAP, and its review of the NSPS that apply to the SOCMI. The EPA is also finalizing amendments to the NSPS for equipment leaks of volatile organic compounds (VOC) in SOCMI based on its reconsideration of certain issues raised in an administrative petition for reconsideration. Furthermore, the EPA is finalizing emission standards for ethylene oxide (EtO) emissions and chloroprene emissions after considering the results of a risk assessment for the HON and for Neoprene Production processes subject to the P&R I NESHAP, and is finalizing a fenceline monitoring work practice standard for certain hazardous air pollutants (HAP). Lastly, the EPA is finalizing the removal of exemptions from standards for periods of startup, shutdown, and malfunction (SSM), adding work practice standards for such periods where appropriate, finalizing standards for previously unregulated HAP, and adding provisions for electronic reporting of performance test reports and periodic reports.

DATES:

This final rule is effective on July 15, 2024. The incorporation by reference (IBR) of certain publications listed in the rule is approved by the Director of the Federal Register as of July 15, 2024. The incorporation by reference of certain other material listed in the rule was approved by the Director of the Federal Register as of October 17, 2000 and November 16, 2007.

ADDRESSES:

The U.S. Environmental Protection Agency (EPA) has established a docket for this action under Docket ID No. EPA-HQ-OAR-2022-0730. All documents in the docket are listed on the https://www.regulations.gov/ website. Although listed, some information is not publicly available, e.g., Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy form. Publicly available docket materials are available either electronically through https://www.regulations.gov/ , or in hard copy at the EPA Docket Center, WJC West Building, Room Number 3334, 1301 Constitution Ave. NW, Washington, DC. The Public Reading Room hours of operation are 8:30 a.m. to 4:30 p.m. Eastern Standard Time, Monday through Friday. The telephone number for the Public Reading Room is (202) 566-1744, and the telephone number for the EPA Docket Center is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT:

For questions about the HON and SOCMI NSPS, contact U.S. EPA, Attn: Mr. Andrew Bouchard, Mail Drop: Sector Policies and Programs Division (E143-01), 109 T.W. Alexander Drive, P.O. Box 12055, RTP, North Carolina 27711; telephone number: (919) 541-4036; and email address: bouchard.andrew@epa.gov. For questions about the P&R I and P&R II NESHAP, contact U.S. EPA, Attn: Ms. Njeri Moeller, Mail Drop: Sector Policies and Programs Division (E143-01), 109 T.W. Alexander Drive, P.O. Box 12055, RTP, North Carolina 27711; telephone number: (919) 541-1380; and email address: moeller.njeri@epa.gov. For specific information regarding the risk modeling methodology, contact U.S. EPA, Attn: Mr. Matthew Woody, Mail Drop: Health and Environmental Impacts Division (C539-02), 109 T.W. Alexander Drive, P.O. Box 12055, RTP, North Carolina 27711; telephone number: (919) 541-1535; and email address: woody.matthew@epa.gov.

SUPPLEMENTARY INFORMATION:

Preamble acronyms and abbreviations. We use multiple acronyms and terms in this preamble. While this list may not be exhaustive, to ease the reading of this preamble and for reference purposes, the EPA defines the following terms and acronyms here:

ACS American Community Survey

AERMOD American Meteorological Society/EPA Regulatory Model dispersion modeling system

ANSI American National Standards Institute

APCD air pollution control device

API American Petroleum Institute

ASME American Society of Mechanical Engineers

BACT best available control technology

BLR basic liquid epoxy resins

BPT benefit per-ton

BSER best system of emissions reduction

BTEX benzene, toluene, ethylbenzene, and xylenes

CAA Clean Air Act

CBI confidential business information

CDX Central Data Exchange

CEDRI Compliance and Emissions Data Reporting Interface

CFR Code of Federal Regulations

CMPU chemical manufacturing process unit

CO carbon monoxide

CO₂ carbon dioxide

CPI consumer price index

CRA Congressional Review Act

EAV equivalent annual value

ECHO Enforcement and Compliance History Online

EFR external floating roof

EIS Emission Information System

EPA Environmental Protection Agency

EPPU elastomer product process unit

ERT Electronic Reporting Tool

EtO ethylene oxide

FTIR fourier transform infrared

HAP hazardous air pollutant(s)

HON Hazardous Organic NESHAP

HQ hazard quotient

HQ_REL hazard quotient reference exposure level

IBR incorporation by reference

ICR information collection request

IFR internal floating roof

IRIS Integrated Risk Information System

ISA Integrated Science Assessment

km kilometer

LAER lowest achievable emissions rate

lb/hr pound per hour

lb/yr pound per year

LDAR leak detection and repair

LDEQ Louisiana Department of Environmental Quality

LEL lower explosive limit

MACT maximum achievable control technology

MDL method detection limit

MERP monomer emission reduction project

MIR maximum individual lifetime [cancer] risk

MON Miscellaneous Organic Chemical Manufacturing NESHAP

MTVP maximum true vapor pressure

NAICS North American Industry Classification System

NAAQS National Ambient Air Quality Standards

NATTS National Air Toxic Trends Station

NEI National Emissions Inventory

NESHAP national emission standards for hazardous air pollutants

NO_X nitrogen oxides

N₂ O nitrous oxide

NPDES national pollutant discharge elimination system

NRDC Natural Resources Defense Council

NSPS new source performance standards

NTTAA National Technology Transfer and Advancement Act

NYSDEC New York State Department of Environmental Conservation

OAR Office of Air and Radiation

OEL open-ended valves or lines

OGI optical gas imaging

OIG Office of Inspector General

OMB Office of Management and Budget

P&R I Group I Polymers and Resins

P&R II Group II Polymers and Resins

PDF portable document format

PMPU polyether polyol manufacturing process unit

POM polycyclic organic matter

ppbv parts per billion by volume

ppm parts per million

ppmv parts per million by volume

ppmw parts per million by weight

PRA Paperwork Reduction Act

psig pounds per square inch gauge

PRD pressure relief device

PV present value

RACT reasonably available control technology

RDL representative detection limit

REL reference exposure level

RFA Regulatory Flexibility Act

RIA Regulatory Impact Analysis

RTO regenerative thermal oxidizer

RTR risk and technology review

SCAQMD South Coast Air Quality Management District

scfm standard cubic feet per minute

scmm standard cubic meter per minute

SOCMI Synthetic Organic Chemical Manufacturing Industry

SO₂ sulfur dioxide

SSM startup, shutdown, and malfunction

TAC Texas Administrative Code

TCEQ Texas Commission on Environmental Quality

TCI total capital investment

TOC total organic compounds

TOSHI target organ-specific hazard index

tpy tons per year

TRE total resource effectiveness

TRI Toxics Release Inventory

UMRA Unfunded Mandates Reform Act

URE unit risk estimate

U.S.C. United States Code

VCS voluntary consensus standards

VOC volatile organic compound(s)

WSR wet strength resins

WWTP wastewater treatment plant

Background information. On April 25, 2023, the EPA proposed amendments to the NSPS that apply to the SOCMI, and amendments to the HON and P&R I and P&R II NESHAP. In this action, we are finalizing decisions and revisions for the rule. We summarize some of the more significant comments we timely received regarding the proposed rule and provide our responses in this preamble. A summary of all other public comments on the proposal and the EPA's responses to those comments is available in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, Docket ID No. EPA-HQ-OAR-2022-0730. A “track changes” version of the regulatory language that incorporates the changes in this action is available in the docket.

Organization of this document.

The information in this preamble is organized as follows:

I. General Information

A. Executive Summary

B. Does this action apply to me?

C. Where can I get a copy of this document and other related information?

D. Judicial Review and Administrative Reconsideration

II. Background

A. What is the statutory authority for this action?

B. What are the source categories and how did the previous standards regulate emissions?

C. What changes did we propose in our April 25, 2023, proposal?

III. What is included in this final rule?

A. What are the final rule amendments based on the risk review for the SOCMI and Neoprene Production source categories NESHAP?

B. What are the final rule amendments based on the technology review for the SOCMI, P&R I, and P&R II source categories NESHAP pursuant to CAA section 112(d)(6) and NSPS reviews for the SOCMI source category pursuant to CAA section 111(b)(1)(B)?

C. What are the final rule amendments pursuant to CAA sections 112(d)(2) and (3), and 112(h) for the SOCMI, P&R I, and P&R II source categories?

D. What are the final rule amendments addressing emissions during periods of SSM?

E. What are the final amendments addressing the NSPS Subparts VV and VVa reconsideration?

F. What other changes have been made to the NESHAP and NSPS?

G. What are the effective and compliance dates of the standards?

IV. What is the rationale for our final decisions and amendments for the SOCMI, P&R I, and P&R II source categories?

A. Residual Risk Review for the SOCMI and Neoprene Production Source Categories NESHAP

B. Technology Review for the SOCMI, P&R I, and P&R II Source Categories NESHAP and NSPS Review for the SOCMI Source Category

C. Amendments Pursuant to CAA Section 112(d)(2) and (3) and 112(h) for the SOCMI, P&R I, and P&R II Source Categories NESHAP

D. Amendments Addressing Emissions During Periods of SSM

E. Amendments Addressing NSPS Subparts VV and VVa Reconsideration

F. Other Amendments to the NESHAP and NSPS

V. Summary of Cost, Environmental, and Economic Impacts and Additional Analyses Conducted

A. What are the affected sources?

B. What are the air quality impacts?

C. What are the cost impacts?

D. What are the economic impacts?

E. What are the benefits?

F. What analysis of environmental justice did we conduct?

G. Children's Environmental Health

VI. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 14094: Modernizing Regulatory Review

B. Paperwork Reduction Act (PRA)

C. Regulatory Flexibility Act (RFA)

D. Unfunded Mandates Reform Act (UMRA)

E. Executive Order 13132: Federalism

F. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments

G. Executive Order 13045: Protection of Children from Environmental Health Risks and Safety Risks

H. Executive Order 13211: Actions Concerning Regulations that Significantly Affect Energy Supply, Distribution, or Use

I. National Technology Transfer and Advancement Act (NTTAA) and 1 CFR part 51

J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations and Executive Order 14096: Revitalizing Our Nation's Commitment to Environmental Justice for All

K. Congressional Review Act (CRA)

I. General Information

A. Executive Summary

1. Purpose of the Regulatory Action

The source categories that are the subject of this final action are the SOCMI and various polymers and resins manufacturing source categories. The SOCMI source category includes chemical manufacturing processes producing commodity chemicals while the polymers and resins manufacturing source categories covered in this action include elastomers production processes and resin production processes that use epichlorohydrin feedstocks (see sections I.B and II.B of this preamble for detailed information about these source categories). The EPA has previously promulgated maximum achievable control technology (MACT) standards for certain processes in the SOCMI source category in the HON rulemaking at 40 Code of Federal Regulations (CFR) part 63, subparts F, G, and H. In 1994, the EPA finalized MACT standards in subparts F, G, and H for SOCMI processes (59 FR 19454), and the Agency completed a residual risk and technology review (RTR) for these NESHAP in 2006 (71 FR 76603). In 1995, the EPA finalized MACT standards in the P&R II NESHAP (40 CFR part 63, subpart W) for epoxy resin and non-nylon polyamide resin manufacturing processes (60 FR 12670), and the Agency completed a residual RTR for these standards in 2008 (73 FR 76220). In 1996, the EPA finalized MACT standards in the P&R I NESHAP (40 CFR part 63, subpart U) for various elastomer manufacturing processes (61 FR 46906), and the Agency completed residual RTRs for these standards in 2008 and 2011 (73 FR 76220 and 76 FR 22566).

The EPA has also promulgated NSPS for certain processes in the SOCMI source category. In 1983, the EPA finalized NSPS (40 CFR part 60, subpart VV) for equipment leaks of VOC in SOCMI (48 FR 48328). In 1990, the EPA finalized NSPS (40 CFR part 60, subparts III and NNN) for VOC from air oxidation unit processes and distillation operations (55 FR 26912 and 55 FR 26931). In 1993, the EPA finalized NSPS (40 CFR part 60, subpart RRR) for VOC from reactor processes (58 FR 45948). In 2007, the EPA promulgated NSPS (40 CFR part 60, subpart VVa) for VOC from certain equipment leaks (72 FR 64883), which reflect the EPA's review and revision of the standards in 40 CFR part 60, subpart VV.

The statutory authority for this action is sections 111, 112, 301(a)(1), and 307(d)(7)(B) of the CAA. Section 111(b)(1)(B) of the CAA requires the EPA to promulgate standards of performance for new sources in any category of stationary sources that the Administrator has listed pursuant to 111(b)(1)(A). Section 111(a)(1) of the CAA provides that these performance standards are to “reflect[ ] the degree of emission limitation achievable through the application of the best system of emission reduction which (taking into account the cost of achieving such reduction and any nonair quality health and environmental impact and energy requirements) the Administrator determines has been adequately demonstrated.” We refer to this level of control as the best system of emissions reduction or “BSER.” Section 111(b)(1)(B) of the CAA requires the EPA to “at least every 8 years, review and, if appropriate, revise” the NSPS.

For NESHAP, CAA section 112(d)(2) requires the EPA to establish MACT standards for listed categories of major sources of HAP. Section 112(d)(6) of the CAA requires the EPA to review standards promulgated under CAA section 112, and revise them “as necessary (taking into account developments in practices, processes, and control technologies),” no less often than every eight years following promulgation of those standards. This is referred to as a “technology review” and is required for all standards established under CAA section 112. Section 112(f) of the CAA requires the EPA to assess the risk to public health remaining after the implementation of MACT emission standards promulgated under CAA section 112(d)(2). If the MACT standards for a source category do not provide “an ample margin of safety to protect public health,” the EPA must also promulgate health-based standards for that source category to further reduce risk from HAP emissions.

Section 301(a)(1) of the CAA authorizes the Administrator to prescribe such regulations as are necessary to carry out his functions under the CAA. Section 307(d)(7)(B) of the CAA requires the reconsideration of a rule only if the person raising an objection to the rule can demonstrate that it was impracticable to raise such objection during the period for public comment or if the grounds for the objection arose after the comment period (but within the time specified for judicial review), and if the objection is of central relevance to the outcome of the rule.

The final new NSPS for SOCMI equipment leaks, air oxidation unit processes, distillation operations, and reactor processes ( i.e., NSPS subparts VVb, IIIa, NNNa, and RRRa, respectively) are based on the Agency's review of the current NSPS (subparts VVa, III, NNN, and RRR) pursuant to CAA section 111(b)(1)(B), which requires that the EPA review the NSPS every eight years and, if appropriate, revise them. In addition, the EPA is finalizing amendments to the NSPS for equipment leaks of VOC in SOCMI based on its reconsideration of certain aspects of subparts VV and VVa that were raised in an administrative petition which the Agency granted pursuant to section 307(d)(7)(B) of the CAA. The final amendments to the HON (NESHAP subparts F, G, H, and I), the P&R I NESHAP (NESHAP subpart U), and the P&R II NESHAP (NESHAP subpart W) are based on the Agency's review of the current NESHAP (subparts F, G, H, I, U, and W) pursuant to CAA sections 112(d) and (f).

Due to the development of the EPA's Integrated Risk Information System (IRIS) inhalation unit risk estimate (URE) for chloroprene in 2010, the EPA conducted a second CAA section 112(f) risk review for the SOCMI source category and Neoprene Production source category. In the first step of the CAA section 112(f)(2) determination of risk acceptability for this rulemaking, the use of the 2010 chloroprene risk value resulted in the EPA identifying unacceptable cancer risk driven by chloroprene emissions from the sole affected source producing neoprene subject to the P&R I NESHAP. Consequently, the final amendments to the P&R I NESHAP address the EPA review of additional control technologies, beyond those analyzed in the technology review conducted for the P&R I source category, to address the unacceptable risk and achieve an ample margin of safety to protect public health at that affected source.

Additionally, in 2016, the EPA updated the IRIS inhalation URE for EtO. In the first step of the CAA section 112(f)(2) determination of risk acceptability for this rulemaking, the use of the updated 2016 EtO risk value resulted in the EPA identifying unacceptable cancer risk driven by EtO emissions from HON processes. Consequently, the final amendments to the HON also address the EPA review of additional control technologies, beyond those analyzed in the technology review conducted for the SOCMI source category, to address the unacceptable risk and achieve an ample margin of safety to protect public health at SOCMI and P&R I affected sources.

2. Summary of the Major Provisions of the Regulatory Action In Question

The most significant amendments that we are finalizing are described briefly below. However, all of our final amendments, including amendments to remove exemptions for periods of SSM, are discussed in detail with rationale in section IV of this preamble or in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

a. HON

We are finalizing amendments to the HON for heat exchange systems, process vents, storage vessels, transfer racks, wastewater, and equipment leaks.

i. NESHAP Subpart F

• As detailed in section II.B.1.a of this preamble, NESHAP subpart F contains provisions to determine which chemical manufacturing processes at a facility are subject to the HON, monitoring requirements for HAP (i.e., HAP listed in Table 4 of NESHAP subpart F) that may leak into cooling water from heat exchange systems, and requirements for maintenance wastewater. For NESHAP subpart F, we are finalizing:
• compliance dates for all of the HON requirements in this action (see40 CFR 63.100(k)(10) through (12); and section III.G of this preamble).
• the moving of all the definitions from NESHAP subparts G and H (i.e., 40 CFR 63.111 and 40 CFR 63.161, respectively) into the definition section of NESHAP subpart F (see 40 CFR 63.101; and sections III.F and IV.F of this preamble).
• a new definition for “in ethylene oxide service” (for equipment leaks, heat exchange systems, process vents, storage vessels, and wastewater) (see40 CFR 63.101; and sections III.A and IV.A of this preamble).
• new operating and monitoring requirements for flares (see40 CFR 63.108; and sections III.C and IV.C of this preamble).
• sampling and analysis procedures for owners and operators to demonstrate that process equipment does, or does not, meet the definition of being “in ethylene oxide service” (see40 CFR 63.109; and sections III.A and IV.A of this preamble).

For heat exchange systems, we are finalizing:

• requirements that owners or operators must use the Modified El Paso Method and repair leaks of total strippable hydrocarbon concentration (as methane) in the stripping gas of 6.2 parts per million by volume (ppmv) or greater (see40 CFR 63.104(g) through (j); and sections III.B.1 and IV.B of this preamble).
• requirements for heat exchange systems in EtO service that owners or operators must conduct more frequent leak monitoring (weekly instead of quarterly) and repair leaks of total strippable hydrocarbon concentration (as methane) in the stripping gas of 6.2 ppmv or greater within 15 days from the sampling date (in lieu of the previous 45-day repair requirement after receiving results of monitoring indicating a leak in the HON), and delay of repair is not allowed unless the equipment can be isolated such that it is no longer in EtO service (see40 CFR 63.104(g)(6) and (h)(6); and sections III.A.1 and IV.A of this preamble).
• a provision allowing use of the previous leak monitoring requirements for heat exchange systems at40 CFR 63.104(b) in limited instances in lieu of using the Modified El Paso Method for heat exchange systems cooling process fluids that will remain in the cooling water if a leak occurs (see 40 CFR 63.104(l); and sections III.B.1 and IV.B of this preamble).

ii. NESHAP Subpart G

As detailed in section II.B.1.b of this preamble, NESHAP subpart G contains requirements for process vents, storage vessels, transfer racks, wastewater streams, and closed vent systems.

For process vents, we are finalizing:

• the removal of the 50 ppmv and 0.005 standard cubic meter per minute (scmm) Group 1 process vent thresholds from the Group 1 process vent definition, and instead we are requiring owners and operators of process vents that emit greater than or equal to 1.0 pound per hour (lb/hr) of total organic HAP to reduce emissions of organic HAP using a flare meeting the operating and monitoring requirements for flares in NESHAP subpart F; or reduce emissions of total organic HAP or total organic compounds (TOC) by 98 percent by weight or to an exit concentration of 20 ppmv, (see40 CFR 63.101 and 40 CFR 63.113(a)(1) and (2); and sections III.B.1 and IV.B of this preamble).
• the removal of the total resource effectiveness (TRE) concept in its entirety (see40 CFR 63.113(a)(4); and sections III.B.1 and IV.B of this preamble).
• an emission standard of 0.054 nanograms per dry standard cubic meter (ng/dscm) at 3 percent oxygen (toxic equivalency basis) for dioxins and furans from chlorinated process vents (see40 CFR 63.113(a)(5); and sections III.C and IV.C of this preamble).
• requirements that owners and operators must reduce emissions of EtO from process vents in EtO service by either: (1) Venting emissions through a closed-vent system to a control device that reduces EtO by greater than or equal to 99.9 percent by weight, to a concentration less than 1 ppmv for each process vent, or to less than 5 pound per year (lb/yr) for all combined process vents per chemical manufacturing process unit (CMPU); or (2) venting emissions through a closed-vent system to a flare meeting the operating and monitoring requirements for flares in NESHAP subpart F (see40 CFR 63.113(j), 40 CFR 63.108, and 40 CFR 63.124; and sections III.A.1 and IV.A of this preamble).

• a work practice standard for maintenance vents requiring that, prior to opening process equipment to the atmosphere, the equipment must either: (1) Be drained and purged to a closed system so that the hydrocarbon content is less than or equal to 10 percent of the lower explosive limit (LEL); (2) be opened and vented to the atmosphere only if the 10-percent LEL cannot be demonstrated and the pressure is less than or equal to 5 pounds per square inch gauge (psig), provided there is no active purging of the equipment to the atmosphere until the LEL criterion is met; (3) be opened when there is less than 50 lbs of VOC that may be emitted to the atmosphere; or (4) for installing or removing an equipment blind, depressurize the equipment to 2 psig or less and maintain pressure of the equipment where purge gas enters the equipment at or below 2 psig during the blind flange installation, provided none of the other work practice standards can be met (see40 CFR 63.113(k); and sections III.C and IV.C of this preamble).
• requirements that owners and operators of process vents in EtO service are allowed to use the maintenance vent work practice standards; however, owners and operators are prohibited from releasing more than 1.0 ton of EtO from all maintenance vents combined on a facility basis in any consecutive 12-month period (see40 CFR 63.113(k)(4); and sections III.A.1 and IV.A of this preamble).

For storage vessels, we are finalizing:

• requirements that owners and operators must reduce emissions of EtO from storage vessels in EtO service by either: (1) Venting emissions through a closed-vent system to a control device that reduces EtO by greater than or equal to 99.9 percent by weight or to a concentration less than 1 ppmv for each storage vessel vent; or (2) venting emissions through a closed-vent system to a flare meeting the operating and monitoring requirements for flares in NESHAP subpart F (see40 CFR 63.119(a)(5), 40 CFR 63.108, and 40 CFR 63.124; and sections III.A.1 and IV.A of this preamble).

• a work practice standard to allow storage vessels to be vented to the atmosphere once a storage vessel degassing concentration threshold is met (i.e., once a storage vessel degassing organic HAP concentration of 5,000 ppmv as methane is met, or until the vapor space concentration is less than 10 percent of the LEL) and all standing liquid has been removed from the vessel to the extent practicable (see 40 CFR 63.119(a)(6); and sections III.C and IV.C of this preamble).
• a definition for “pressure vessel” and removing the exemption for “pressure vessels designed to operate in excess of 204.9 kilopascals and without emissions to the atmosphere” from the definition of storage vessel (see40 CFR 63.101); and requirements for initial and annual performance testing of pressure vessels that are considered Group 1 storage vessels using EPA Method 21 of 40 CFR part 60, appendix A-7 to demonstrate no detectable emissions ( i.e., required to meet a leak definition of 500 parts per million (ppm) at each point on the pressure vessel where total organic HAP could potentially be emitted) (see 40 CFR 63.119(a)(7); and sections III.C and IV.C of this preamble).
• requirements that all openings in an internal floating roof (IFR) (except those for automatic bleeder vents (vacuum breaker vents), rim space vents, leg sleeves, and deck drains) be equipped with a deck cover; and that the deck cover be equipped with a gasket between the cover and the deck (see40 CFR 63.119(b)(5)(ix); and sections III.B.1 and IV.B of this preamble).
• control requirements for guidepoles for all storage vessels equipped with an IFR (see40 CFR 63.119(b)(5)(x), (xi), and (xii); and sections III.B.1 and IV.B of this preamble).
• a work practice standard that applies during periods of planned routine maintenance of a control device, fuel gas system, or process equipment that is normally used for compliance with the storage vessel emissions control requirements; owners and operators are not permitted to fill the storage vessel during these periods (such that working losses are controlled and the vessel only emits HAP to the atmosphere due to breathing losses for a limited amount of time) (see40 CFR 63.119(e)(7); and sections III.C and IV.C of this preamble).
• revisions to the Group 1 storage capacity criterion (for storage vessels at existing sources) from between 75 cubic meters (m³ ) and 151 m³ to between 38 m³ and 151 m³ (see Table 5 to subpart G; and sections III.B.1 and IV.B of this preamble).
• revisions to the Group 1 stored-liquid maximum true vapor pressure (MTVP) of total organic HAP threshold (for storage vessels at existing and new sources) from greater than or equal to 13.1 kilopascals to greater than or equal to 6.9 kilopascals (see Tables 5 and 6 to subpart G; and sections III.B.1 and IV.B of this preamble).

For transfer racks, we are finalizing:

• removing the exemption for transfer operations that load “at an operating pressure greater than 204.9 kilopascals” from the definition of transfer operation (see40 CFR 63.101; and sections III.C and IV.C of this preamble).

For wastewater streams, we are finalizing:

• revisions to the Group 1 wastewater stream threshold to include wastewater streams in EtO service (i.e., wastewater streams with total annual average concentration of EtO greater than or equal to 1 parts per million by weight (ppmw) at any flow rate) (see 40 CFR 63.132(c)(1)(iii) and (d)(1)(ii); and sections III.A and IV.A of this preamble).
• requirements prohibiting owners and operators from injecting wastewater into or disposing of water through any heat exchange system in a CMPU meeting the conditions of40 CFR 63.100(b)(1) through (3) if the water contains any amount of EtO, has been in contact with any process stream containing EtO, or the water is considered wastewater as defined in 40 CFR 63.101 (see 40 CFR 63.104(k); and sections III.A and IV.A of this preamble).

For closed vent systems, we are finalizing:

• requirements that owners and operators may not bypass an air pollution control device (APCD) at any time (see40 CFR 63.114(d)(3), 40 CFR 63.127(d)(3), and 40 CFR 63.148(f)(4)), that a bypass is a violation, and that owners and operators must estimate and report the quantity of organic HAP released (see 40 CFR 63.118(a)(5), 40 CFR 63.130(a)(2)(iv), 40 CFR 63.130(b)(3), 40 CFR 63.130(d)(7), and 40 CFR 63.148(i)(3)(iii) and (j)(4); and sections III.C and IV.C of this preamble).

iii. NESHAP Subparts H and I

As detailed in sections II.B.1.c and II.B.1.d of this preamble, NESHAP subparts H and I contain requirements for equipment leaks. Also, due to space limitations in NESHAP subpart F, we are finalizing fenceline monitoring ( i.e., monitoring along the perimeter of the facility's property line) in NESHAP subpart H for all emission sources. For equipment leaks and fenceline monitoring, we are finalizing:

• requirements that all connectors in EtO service be monitored monthly at a leak definition of 100 ppm with no skip period, and delay of repair is not allowed unless the equipment can be isolated such that it is no longer in EtO service (see40 CFR 63.174(a)(3), (b)(3)(vi), and (g)(3), and 40 CFR 63.171(f); and sections III.A and IV.A of this preamble).
• requirements that all gas/vapor and light liquid valves in EtO service be monitored monthly at a leak definition of 100 ppm with no skip period, and delay of repair is not allowed unless the equipment can be isolated such that it is no longer in EtO service (see40 CFR 63.168(b)(2)(iv) and (d)(5), and 40 CFR 63.171(f); and sections III.A and IV.A of this preamble).
• requirements that all light liquid pumps in EtO service be monitored monthly at a leak definition of 500 ppm, and delay of repair is not allowed unless the equipment can be isolated such that it is no longer in EtO service (see40 CFR 63.163(a)(1)(iii), (b)(2)(iv), (c)(4), and (e)(7), and 40 CFR 63.171(f); and sections III.A and IV.A of this preamble).
• a work practice standard for pressure relief devices (PRDs) that vent to the atmosphere that require owners and operators to implement at least three prevention measures, perform root cause analysis and corrective action in the event that a PRD does release emissions directly to the atmosphere, and monitor PRDs using a system that is capable of identifying and recording the time and duration of each pressure release and of notifying operators that a pressure release has occurred (see40 CFR 63.165(e); and sections III.C and IV.C of this preamble).
• requirements that all surge control vessels and bottoms receivers meet the requirements we are finalizing for process vents (see40 CFR 63.170(b); and sections III.C and IV.C of this preamble).
• requirements that owners and operators may not bypass an APCD at any time (see40 CFR 63.114(d)(3), 40 CFR 63.127(d)(3), and 40 CFR 63.148(f)(4)), that a bypass is a violation, and that owners and operators must estimate and report the quantity of organic HAP released (see 40 CFR 63.118(a)(5), 40 CFR 63.130(a)(2)(iv), 40 CFR 63.130(b)(3), 40 CFR 63.130(d)(7), and 40 CFR 63.148(i)(3)(iii) and (j)(4); and sections III.C and IV.C of this preamble).
• fenceline monitoring work practice standards requiring owners and operators to monitor for any of six specific HAP ( i.e., benzene, 1,3-butadiene, ethylene dichloride, vinyl chloride, EtO, and chloroprene) if their affected source uses, produces, stores, or emits any of them, and conduct root cause analysis and corrective action upon exceeding annual average concentration action levels set forth for each HAP (see 40 CFR 63.184; and sections III.B.1 and IV.B of this preamble).

b. P&R I NESHAP

As detailed in section II.B.2 of this preamble, the P&R I NESHAP (40 CFR part 63, subpart U) generally follows and refers to the requirements of the HON, with additional requirements for batch process vents. We are finalizing amendments to the P&R I NESHAP for heat exchange systems, process vents, storage vessels, wastewater, and equipment leaks. For NESHAP subpart U, we are finalizing:

• compliance dates for all of the requirements in this action related to the P&R I NESHAP (see40 CFR 63.481(n) and (o); and section III.G of this preamble).
• new operating and monitoring requirements for flares (see40 CFR 63.508; and sections III.C and IV.C of this preamble).
• the removal of the provisions to assert an affirmative defense to civil penalties (see40 CFR 63.480(j)(4); and sections III.D and IV.D of this preamble).
• the same fenceline monitoring requirements that we are finalizing in Subpart H for HON sources.
• sampling and analysis procedures for owners and operators of affected sources producing neoprene to demonstrate that process equipment does, or does not, meet the definition of being “in chloroprene service” (see40 CFR 63.509; and sections III.A and IV.A of this preamble).

For heat exchange systems, we are finalizing:

• the same requirements (except for EtO standards) listed in section I.A.2.a.i of this preamble that we are finalizing for heat exchange systems subject to the HON to also apply to heat exchange systems subject to the P&R I NESHAP (see40 CFR 63.502(n)(7); and sections III.B.1 and IV.B of this preamble).

For continuous front-end process vents, we are finalizing:

• the requirement that owners and operators must reduce emissions of chloroprene from continuous front-end process vents in chloroprene service at affected sources producing neoprene by venting emissions through a closed-vent system to a non-flare control device that reduces chloroprene by greater than or equal to 98 percent by weight, to a concentration less than 1 ppmv for each process vent, or to less than 5 lb/yr for all combined process vents per elastomer product process unit (EPPU) (see40 CFR 63.485(y), and 40 CFR 63.510; and sections III.A and IV.A of this preamble).

• the same requirements (except for EtO standards) listed in section I.A.2.a.ii of this preamble that we are finalizing for process vents subject to the HON to also apply to continuous front-end process vents subject to the P&R I NESHAP (see40 CFR 63.482, 40 CFR 63.485(l)(6), (o)(6), (p)(5), and (x), 40 CFR 63.113(a)(1) and (2), 40 CFR 63.113(a)(4), 40 CFR 63.113(k), 40 CFR 63.114(a)(5)(v); and sections III.B.1 and IV.B of this preamble).
• requirements that owners and operators of continuous front-end process vents in chloroprene service are allowed to use the maintenance vent work practice standards; however, owners and operators are prohibited from releasing more than 1.0 ton of chloroprene from all maintenance vents combined on a facility basis in any consecutive 12-month period (see40 CFR 63.485(z); and sections III.A and IV.A of this preamble).
• the same dioxins and furans emission standard that we are finalizing for process vents subject to the HON of 0.054 ng/dscm at 3 percent oxygen (toxic equivalency basis) to also apply to chlorinated continuous front-end process vents (see40 CFR 63.485(x); and sections III.C and IV.C of this preamble).

For batch front-end process vents, we are finalizing:

• the removal of the annual organic HAP emissions mass flow rate, cutoff flow rate, and annual average batch vent flow rate Group 1 process vent thresholds from the Group 1 batch front-end process vent definition (these thresholds were previously determined on an individual batch process vent basis). Instead, owners and operators of batch front-end process vents that release total annual organic HAP emissions greater than or equal to 4,536 kilograms per year (kg/yr) (10,000 pounds per year (lb/yr)) from all batch front-end process vents combined are required to reduce emissions of organic HAP from these process vents using a flare meeting the operating and monitoring requirements for flares; or reduce emissions of organic HAP or total organic carbon (TOC) by 90 percent by weight (or to an exit concentration of 20 ppmv if considered an “aggregate batch vent stream” as defined by the rule) (see40 CFR 63.482, 40 CFR 63.487(e)(1)(iv), 40 CFR 63.488(d)(2), (e)(4), (f)(2), and (g)(3); and sections III.B.1 and IV.B of this preamble).
• the same chloroprene standards that we are finalizing for continuous front-end process for batch front-end process vents at affected sources producing neoprene (see40 CFR 63.487(j); and sections III.A and IV.A of this preamble).
• the same work practice standards that we are finalizing for maintenance vents as described for HON to the P&R I NESHAP (see40 CFR 63.487(i); and sections III.C and IV.C of this preamble).
• requirements that owners and operators of batch front-end process vents in chloroprene service are allowed to use the maintenance vent work practice standards; however, owners and operators are prohibited from releasing more than 1.0 ton of chloroprene from all maintenance vents combined on a facility basis in any consecutive 12-month period (see40 CFR 63.487(i)(4); and sections III.A and IV.A of this preamble).
• the same dioxins and furans emission standard that we are finalizing for process vents subject to the HON of 0.054 ng/dscm at 3 percent oxygen (toxic equivalency basis) to also apply to chlorinated batch front-end process vents (see40 CFR 63.487(a)(3) and (b)(3); and sections III.C and IV.C of this preamble).

For back-end process vents, we are finalizing:

• a requirement that owners and operators reduce emissions of chloroprene from back-end process vents in chloroprene service at affected sources producing neoprene by venting emissions through a closed-vent system to a non-flare control device that reduces chloroprene by greater than or equal to 98 percent by weight, to a concentration less than 1 ppmv for each process vent, or to less than 5 lb/yr for all combined process vents (see40 CFR 63.494(a)(7); and sections III.A and IV.A of this preamble).

For storage vessels, we are finalizing:

• the requirement that owners and operators reduce emissions of chloroprene from storage vessels in chloroprene service at affected sources producing neoprene by venting emissions through a closed-vent system to a non-flare control device that reduces chloroprene by greater than or equal to 98 percent by weight or to a concentration less than 1 ppmv for each storage vessel vent (see 40 CFR 63.484(u) and 40 CFR 63.510; and sections III.A and IV.A of this preamble).

• the same requirements (except for EtO standards) listed in section I.A.2.a.ii of this preamble that we are finalizing for storage vessels subject to the HON except the requirements apply to storage vessels subject to the P&R I NESHAP (see40 CFR 63.484(t); and sections III.B.1 and IV.B of this preamble).

For wastewater streams, we are finalizing:

• the Group 1 wastewater stream threshold to include wastewater streams in chloroprene service at affected sources producing neoprene (i.e., wastewater streams with total annual average concentration of chloroprene greater than or equal to 10 ppmw at any flow rate) (see 40 CFR 63.501(a)(10)(iv); and sections III.A and IV.A of this preamble).
• requirements prohibiting owners and operators from injecting wastewater into or disposing of water through any heat exchange system in an EPPU if the water contains any amount of chloroprene, has been in contact with any process stream containing chloroprene, or the water is considered wastewater as defined in40 CFR 63.482 (see 40 CFR 63.502(n)(8); and sections III.A and IV.A of this preamble).

For equipment leaks and fenceline monitoring, we are finalizing:

• the same requirements (except for EtO standards) listed in section I.A.2.a.iii of this preamble that we are finalizing for equipment leaks subject to the HON except the requirements apply to equipment leaks subject to the P&R I NESHAP (see40 CFR 63.502(a)(1) through (a)(6); and sections III.C and IV.C of this preamble).
• the cross-reference in the P&R I NESHAP to the fenceline monitoring work practice standards in the HON (see40 CFR 63.502) requiring owners and operators to monitor for any of six specific HAP ( i.e., benzene, 1,3-butadiene, ethylene dichloride, vinyl chloride, EtO, and chloroprene) if their affected source uses, produces, stores, or emits any of them, and conduct root cause analysis and corrective action upon exceeding annual average concentration action levels set forth for each HAP (see sections III.B.1 and IV.B of this preamble), plus a lower annual average concentration action level for chloroprene applicable to neoprene production source category (see sections III.A and IV.A of this preamble).

c. P&R II NESHAP

The most significant amendments that we are finalizing for the P&R II NESHAP (40 CFR part 63, subpart W) are requirements for heat exchange systems (see 40 CFR 63.523(d) and 40 CFR 63.524(c); and sections III.C and IV.C of this preamble) and requirements for owners and operators of wet strength resins (WSR) sources to comply with both the equipment leak standards in the HON and the HAP emissions limitation for process vents, storage tanks, and wastewater systems (see 40 CFR 63.524(a)(3) and (b)(3); and sections III.C and IV.C of this preamble). We are also finalizing the same dioxin and furan emission standard of 0.054 ng/dscm at 3 percent oxygen (toxic equivalency basis) for chlorinated process vents as in the HON and the P&R I NESHAP (see 40 CFR 63.523(e) (for process vents associated with each existing, new, or reconstructed affected basic liquid epoxy resins (BLR) source), 40 CFR 63.524(a)(3) (for process vents associated with each existing affected WSR source), and 40 CFR 63.524(b)(3) (for process vents associated with each new or reconstructed affected WSR source); and see sections III.C and IV.C of this preamble).

d. NSPS Subparts III, NNN, and RRR

We are amending the applicability of NSPS subparts III, NNN, and RRR so that they only apply to sources constructed, reconstructed, or modified on or before April 25, 2023. Affected facilities that are constructed, reconstructed, or modified after April 25, 2023, are subject to the new NSPS subparts IIIa, NNNa, and RRRa.

e. NSPS Subparts IIIa, NNNa, and RRRa

Rather than comply with a TRE concept which is used in NSPS subparts III, NNN, and RRR, we are finalizing in new NSPS subparts IIIa, NNNa, and RRRa a requirement for owners and operators to reduce emissions of TOC (minus methane and ethane) from all vent streams of an affected facility ( i.e., SOCMI air oxidation unit processes, distillation operations, and reactor processes for which construction, reconstruction, or modification occurs after April 25, 2023) by 98 percent by weight or to a concentration of 20 ppmv on a dry basis corrected to 3 percent oxygen, or combust the emissions in a flare meeting the same operating and monitoring requirements for flares that we are finalizing for flares subject to the HON. We are finalizing a mass-based exemption criterion of 0.001 lb/hr TOC (for which emission controls are not required) in new NSPS subparts IIIa and NNNa. We are also not including a relief valve discharge exemption in the definition of “vent stream” in new NSPS subparts IIIa, NNNa, and RRRa; instead, any relief valve discharge to the atmosphere of a vent stream is a violation of the emissions standard. In addition, we are finalizing in new NSPS subparts IIIa, NNNa, and RRRa the same work practice standards for maintenance vents that we are finalizing for HON process vents, and the same monitoring requirements that we are finalizing for HON process vents for adsorbers that cannot be regenerated and regenerative adsorbers that are regenerated offsite (see sections III.B.2 and IV.B of this preamble).

f. NSPS Subpart VVa

We are amending certain aspects of NSPS subparts VV and VVa to address issues raised in an administrative petition which the Agency granted pursuant to section 307(d)(7)(B) of the CAA. In addition, we are amending the applicability of the existing NSPS subpart VVa so that it applies to sources constructed, reconstructed, or modified after November 6, 2006, and on or before April 25, 2023. Affected facilities that are constructed, reconstructed, or modified after April 25, 2023, are subject to the new NSPS subpart VVb.

g. NSPS Subpart VVb

We are finalizing in a new NSPS subpart VVb the same requirements in NSPS subpart VVa plus a requirement that all gas/vapor and light liquid valves be monitored quarterly at a leak definition of 100 ppm and all connectors be monitored once every 12 months at a leak definition of 500 ppm (see sections III.B.2 and IV.B of this preamble). For each of these two additional requirements, we are also finalizing skip periods for good performance.

3. Costs and Benefits

Pursuant to E.O. 12866, the EPA prepared an analysis of the potential costs and benefits associated with this action. This analysis, titled Regulatory Impact Analysis for the Final New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry (referred to as the RIA in this document), is available in the docket, and is also briefly summarized in section V of this preamble. The assessment of costs and benefits described herein and in the RIA is presented solely for the purposes of complying with E.O. 12866 and to provide the public with a complete depiction of the impacts of this final action. The EPA notes that analysis of costs and benefits in the RIA is distinct from the determinations finalized in this action under CAA sections 111 and 112, which are based on the statutory factors the EPA is required to consider under those sections.

B. Does this action apply to me?

Regulated entities. Categories and entities potentially regulated by this action are the SOCMI source category (and whose facilities, sources and processes we often refer to as “HON facilities,” “HON sources,” and “HON processes” for purposes of the NESHAP) and several Polymers and Resins Production source categories covered in the P&R I and P&R II NESHAP (see section II.B of this preamble for detailed information about the source categories). The North American Industry Classification System (NAICS) code for SOCMI facilities begins with 325, for P&R I facilities is 325212, and for P&R II facilities is 325211. The list of NAICS codes is not intended to be exhaustive, but rather provides a guide for readers regarding the entities that this final action is likely to affect.

As defined in the Initial List of Categories of Sources Under Section 112(c)(1) of the Clean Air Act Amendments of 1990 (see 57 FR 31576, July 16, 1992) and Documentation for Developing the Initial Source Category List, Final Report (see EPA-450/3-91-030, July 1992), the SOCMI source category is any facility engaged in “manufacturing processes that produce one or more of the chemicals [listed] that either: (1) Use an organic HAP as a reactant or (2) produce an organic HAP as a product, co-product, by-product, or isolated intermediate.” In the development of NESHAP for this source category, the EPA considered emission sources associated with: equipment leaks (including leaks from heat exchange systems), process vents, transfer racks, storage vessels, and wastewater collection and treatment systems. The elastomer production source categories in the P&R I NESHAP and resins produced with epichlorohydrin feedstock in the P&R II NESHAP have many similar emission sources with SOCMI sources and are discussed further in section II.B of this preamble.

The EPA Priority List (40 CFR 60.16, 44 FR 49222, August 21, 1979) included “Synthetic Organic Chemical Manufacturing” as a source category for which standards of performance were to be promulgated under CAA section 111. In the development of NSPS subparts VVa, III, NNN, and RRR for this source category, the EPA considered emission sources associated with unit processes, storage and handling equipment, fugitive emission sources, and secondary sources.

To determine whether your facility is affected, you should examine the applicability criteria in the appropriate NESHAP or NSPS. If you have any questions regarding the applicability of any aspect of these NESHAP and NSPS, please contact the appropriate person listed in the preceding FOR FURTHER INFORMATION CONTACT section of this preamble.

C. Where can I get a copy of this document and other related information?

In addition to being available in the docket, an electronic copy of this final action will also be available on the internet. Following signature by the EPA Administrator, the EPA will post a copy of this final action at: https://www.epa.gov/stationary-sources-air-pollution/synthetic-organic-chemical-manufacturing-industry-organic-national, https://www.epa.gov/stationary-sources-air-pollution/group-i-polymers-and-resins-national-emission-standards-hazardous, and https://www.epa.gov/stationary-sources-air-pollution/epoxy-resins-production-and-non-nylon-polyamides-national-emission. Following publication in the Federal Register , the EPA will post the Federal Register version and key technical documents at these same websites.

Additional information is available on the RTR website at https://www.epa.gov/stationary-sources-air-pollution/risk-and-technology-review-national-emissions-standards-hazardous. This information includes an overview of the RTR program and links to project websites for the RTR source categories.

D. Judicial Review and Administrative Reconsideration

Under CAA section 307(b)(1), judicial review of this final action is available only by filing a petition for review in the United States Court of Appeals for the District of Columbia Circuit (the Court) by July 15, 2024. Under CAA section 307(b)(2), the requirements established by these final rules may not be challenged separately in any civil or criminal proceedings brought to enforce the requirements.

Section 307(d)(7)(B) of the CAA further provides that only an objection to a rule or procedure which was raised with reasonable specificity during the period for public comment (including any public hearing) may be raised during judicial review. This section also provides a mechanism for the EPA to reconsider the rule if the person raising an objection can demonstrate to the Administrator that it was impracticable to raise such objection within the period for public comment or if the grounds for such objection arose after the period for public comment (but within the time specified for judicial review) and if such objection is of central relevance to the outcome of the rule. Any person seeking to make such a demonstration should submit a Petition for Reconsideration to the Office of the Administrator, U.S. EPA, Room 3000, WJC South Building, 1200 Pennsylvania Ave. NW, Washington, DC 20460, with a copy to both the person(s) listed in the preceding FOR FURTHER INFORMATION CONTACT section, and the Associate General Counsel for the Air and Radiation Law Office, Office of General Counsel (Mail Code 2344A), U.S. EPA, 1200 Pennsylvania Ave. NW, Washington, DC 20460.

II. Background

A. What is the statutory authority for this action?

1. NESHAP

The statutory authority for this action related to NESHAP is provided by sections 112 and 301 of the CAA, as amended (42 U.S.C. 7401 et seq.). Section 112 of the CAA establishes a two-stage regulatory process to develop standards for emissions of HAP from stationary sources. “Major sources” are those that emit, or have the potential to emit, any single HAP at a rate of 10 tpy or more, or 25 tpy or more of any combination of HAP. For major sources, these standards are commonly referred to as MACT standards and must reflect the maximum degree of emission reductions of HAP achievable (after considering cost, energy requirements, and non-air quality health and environmental impacts). In developing MACT standards, CAA section 112(d)(2) directs the EPA to consider the application of measures, processes, methods, systems, or techniques, including, but not limited to, those that reduce the volume of or eliminate HAP emissions through process changes, substitution of materials, or other modifications; enclose systems or processes to eliminate emissions; collect, capture, or treat HAP when released from a process, stack, storage, or fugitive emissions point; are design, equipment, work practice, or operational standards; or any combination of the above. The MACT standards may take the form of design, equipment, work practice or operational standards where the EPA first determines either that (1) a pollutant cannot be emitted through a conveyance designed and constructed to emit or capture the pollutant, or that any requirement for, or use of, such a conveyance would be inconsistent with law; or (2) the application of measurement methodology to a particular class of sources is not practicable due to technological and economic limitations. CAA section 112(h)(1)-(2).

For these MACT standards, the statute specifies certain minimum stringency requirements, which are referred to as MACT floor requirements, and which may not be based on cost considerations. See CAA section 112(d)(3). For new sources, the MACT floor cannot be less stringent than the emission control achieved in practice by the best-controlled similar source. The MACT standards for existing sources can be less stringent than floors for new sources, but they cannot be less stringent than the average emission limitation achieved by the best-performing 12 percent of existing sources in the category or subcategory (or the best-performing five sources for categories or subcategories with fewer than 30 sources). In developing MACT standards, we must also consider control options that are more stringent than the floor under CAA section 112(d)(2). We may establish standards more stringent than the floor, based on the consideration of the cost of achieving the emissions reductions, any non-air quality health and environmental impacts, and energy requirements.

In the second stage of the regulatory process, the CAA requires the EPA to undertake two different analyses, which we refer to as the technology review and the residual risk review. Under the technology review, we must review the technology-based standards and revise them “as necessary (taking into account developments in practices, processes, and control technologies)” no less frequently than every 8 years, pursuant to CAA section 112(d)(6). In conducting this review, the EPA is not required to recalculate the MACT floors that were established in earlier rulemakings. Natural Resources Defense Council (NRDC) v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008); Association of Battery Recyclers, Inc. v. EPA, 716 F.3d 667 (D.C. Cir. 2013). The EPA may consider cost in deciding whether to revise the standards pursuant to CAA section 112(d)(6). The EPA is required to address regulatory gaps, such as missing standards for listed air toxics known to be emitted from the source category, and any new MACT standards must be established under CAA sections 112(d)(2) and (3), or, in specific circumstances, CAA sections 112(d)(4) or (h). Louisiana Environmental Action Network v. EPA, 955 F.3d 1088 (D.C. Cir. 2020). Under the residual risk review, we must evaluate the risk to public health remaining after application of the technology-based standards and revise the standards, if necessary, to provide an ample margin of safety to protect public health or to prevent, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect. The residual risk review is required within 8 years after promulgation of the MACT standards, pursuant to CAA section 112(f). In conducting the residual risk review, if the EPA determines that the current standards provide an ample margin of safety to protect public health, it is not necessary to revise the MACT standards pursuant to CAA section 112(f). For more information on the statutory authority for this rule, see 88 FR 25080, April 25, 2023. Often, the CAA section 112(d)(6) technology review and the CAA section 112(f)(2) residual risk review are combined into a single rulemaking action, commonly called a “risk and technology review” (RTR).

The EPA conducted a combined RTR for the HON in 2006, concluding that there was no need to revise the HON under the provisions of either CAA section 112(f) or 112(d)(6). As part of the residual risk review, the EPA conducted a risk assessment and, based on the results of the risk assessment, determined that the then-current level of control called for by the existing MACT standards both reduced HAP emissions to levels that presented an acceptable level of risk and provided an ample margin of safety to protect public health (see 71 FR 76603, December 21, 2006 for additional details). In 2008, the EPA conducted a combined RTR for four of the P&R I source categories (including the Polysulfide Rubber Production, Ethylene-Propylene Elastomers Production, Butyl Rubber Production, and Neoprene Production source categories) and all P&R II source categories (Epoxy Resins Production and Non-Nylon Polyamides Production source categories). In 2011, the EPA completed the combined RTR for the remaining five P&R I source categories (Epichlorohydrin Elastomers Production, Hypalon Production, Polybutadiene Rubber Production, Styrene-Butadiene Rubber and Latex Production, and Nitrile Butadiene Rubber Production). The EPA concluded in these actions that there was no need to revise standards for any of the nine P&R I source categories and two P&R II source categories under the provisions of either CAA section 112(f) or 112(d)(6) (see 73 FR 76220, December 16, 2008 and 77 FR 22566, April 21, 2011 for additional details).

This action constitutes another CAA section 112(d)(6) technology review for the HON and the P&R I and P&R II NESHAP. This action also constitutes an updated CAA section 112(f) risk review based on new information for the HON and for affected sources producing neoprene subject to the P&R I NESHAP. We note that although there is no statutory CAA obligation under CAA section 112(f) for the EPA to conduct a second residual risk review of the HON or of standards for affected sources producing neoprene subject to the P&R I NESHAP, the EPA retains discretion to revisit its residual risk reviews where the Agency deems that to be warranted. See, e.g., Fed. Commc'ns Comm'n v. Fox Television Stations, Inc., 556 U.S. 502, 515 (2009); Motor Vehicle Mfrs. Ass'n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 42 (1983); Ethylene Oxide Emissions Standards for Sterilization Facilities; Final Decision, 71 FR 17712, 17715 col. 1 (April 7, 2006) (asserting authority, in residual risk review for EtO, for EPA “to revisit (and revise, if necessary) any rulemaking if there is sufficient evidence that changes within the affected industry or significant improvements to science suggests the public is exposed to significant increases in risk as compared to the risk assessment prepared for the rulemaking ( e.g., CAA section 301).”).

Here, the specific changes to health information related to certain pollutants emitted by these unique categories led us to determine that it is appropriate, in this case, to conduct these second residual risk reviews under CAA section 112(f). In particular, the EPA is concerned about the cancer risks posed by the SOCMI source category due to the EPA's 2016 updated IRIS inhalation URE for EtO, which shows EtO to be significantly more toxic than previously known. This updated URE was not available in 2006, when the EPA conducted its last RTR, but if this URE had been available, the EPA would almost undoubtedly have reached different conclusions about risk acceptability and the need to modify the standards to provide an ample margin of safety to protect public health. Similarly, for chloroprene, when the EPA conducted the first residual risk assessment for the SOCMI and Neoprene Production source categories, there was no inhalation URE for chloroprene. Therefore, in those risk reviews, the EPA attributed no cancer risk to chloroprene. The EPA concluded development of the IRIS inhalation URE for chloroprene in 2010. That URE allows us to assess, for the first time, the cancer risks posed by chloroprene. Had the EPA had the benefit of this new URE at the time it conducted the 2006 and 2008 RTRs, the URE would almost undoubtedly have impacted our conclusions about risk acceptability and the P&R I standards' provision of an ample margin of safety to protect public health. Instead, we are conducting that analysis in this action.

In order to ensure our standards provide an ample margin of safety to protect public health following the new IRIS inhalation UREs for EtO and chloroprene, we are exercising our discretion and conducting risk assessments in this action for HON sources and for affected sources producing neoprene subject to the P&R I NESHAP. Finally, we note that on September 15, 2021, the EPA partially granted a citizen administrative petition requesting that the EPA conduct a second residual risk review under CAA section 112(f)(2) for the HON, stating our intent to conduct a human health risk assessment concurrently with the section 112(d)(6) review. Likewise, on March 4, 2022, the EPA partially granted another citizen administrative petition requesting that the EPA also conduct a second residual risk review under CAA section 112(f) for the Neoprene Production source category in the P&R I NESHAP, stating that we intend to conduct a human health risk assessment concurrently with the section 112(d)(6) review. This final rulemaking is partly undertaken in response to those citizen administrative petitions. In sum, even though we do not have a mandatory duty to conduct repeated residual risk reviews under CAA section 112(f)(2), we have the authority to revisit any rulemaking if there is: (1) Significant new scientific information suggesting the public is exposed to higher risks from facilities subject to the HON and the P&R I and P&R II NESHAP than previously realized, as compared to the previous risk assessments prepared for earlier rulemakings, or (2) sufficient evidence that changes within the affected industry are exposing the public to new risks.

2. NSPS

The EPA's authority for the final NSPS rules is CAA section 111, which governs the establishment of standards of performance for stationary sources. Section 111(b)(1)(A) of the CAA requires the EPA Administrator to list categories of stationary sources that in the Administrator's judgment cause or contribute significantly to air pollution that may reasonably be anticipated to endanger public health or welfare. The EPA must then issue performance standards for new (and modified or reconstructed) sources in each source category pursuant to CAA section 111(b)(1)(B). These standards are referred to as new source performance standards, or NSPS. The EPA has the authority to define the scope of the source categories, determine the pollutants for which standards should be developed, set the emission level of the standards, and distinguish among classes, types, and sizes within categories in establishing the standards.

CAA section 111(b)(1)(B) requires the EPA to “at least every 8 years review and, if appropriate, revise” NSPS. However, the Administrator need not review any such standard if the “Administrator determines that such review is not appropriate in light of readily available information on the efficacy” of the standard. When conducting a review of an existing performance standard, the EPA has the discretion and authority to add emission limits for pollutants or emission sources not currently regulated for that source category.

In setting or revising a performance standard, CAA section 111(a)(1) provides that performance standards are to reflect “the degree of emission limitation achievable through the application of the BSER which (taking into account the cost of achieving such reduction and any nonair quality health and environmental impact and energy requirements) the Administrator determines has been adequately demonstrated.” The term “standard of performance” in CAA section 111(a)(1) makes clear that the EPA is to determine both the BSER for the regulated sources in the source category and the degree of emission limitation achievable through application of the BSER. The EPA must then, under CAA section 111(b)(1)(B), promulgate standards of performance for new sources that reflect that level of stringency. CAA section 111(h)(1) authorizes the Administrator to promulgate “a design, equipment, work practice, or operational standard, or combination thereof” if in his or her judgment, “it is not feasible to prescribe or enforce a standard of performance.” CAA section 111(h)(2) provides the circumstances under which prescribing or enforcing a standard of performance is “not feasible,” such as, when the pollutant cannot be emitted through a conveyance designed to emit or capture the pollutant, or when there is no practicable measurement methodology for the particular class of sources. CAA section 111(b)(5) precludes the EPA from prescribing a particular technological system that must be used to comply with a standard of performance. Rather, sources can select any measure or combination of measures that will achieve the standard.

Pursuant to the definition of new source in CAA section 111(a)(2), standards of performance apply to facilities that begin construction, reconstruction, or modification after the date of publication of the proposed standards in the Federal Register . Under CAA section 111(a)(4), “modification” means any physical change in, or change in the method of operation of, a stationary source which increases the amount of any air pollutant emitted by such source or which results in the emission of any air pollutant not previously emitted. Changes to an existing facility that do not result in an increase in emissions are not considered modifications. Under the provisions in 40 CFR 60.15, reconstruction means the replacement of components of an existing facility such that: (1) The fixed capital cost of the new components exceeds 50 percent of the fixed capital cost that would be required to construct a comparable entirely new facility; and (2) it is technologically and economically feasible to meet the applicable standards.

In the development of NSPS for the SOCMI source category, the EPA considered emission sources associated with unit processes, storage and handling equipment, fugitive emission sources, and secondary sources. In 1983, the EPA promulgated NSPS for VOC from equipment leaks in SOCMI (40 CFR part 60, subpart VV). In 1990, the EPA promulgated NSPS (40 CFR part 60, subparts III and NNN) for VOC from air oxidation unit processes and distillation operations in the SOCMI (55 FR 26912 and 55 FR 26931). In 1993, the EPA promulgated NSPS (40 CFR part 60, subpart RRR) for VOC from reactor processes in the SOCMI (58 FR 45948). In 2007, based on its review of NSPS subpart VV, the EPA promulgated certain amendments to NSPS subpart VV and new NSPS (40 CFR part 60, subpart VVa) for VOC from certain equipment leaks in the SOCMI (72 FR 64883). This final action presents the required CAA 111(b)(1)(B) review of the NSPS for the air oxidation unit processes (subpart III), distillation operations (subpart NNN), reactor processes (subpart RRR), and equipment leaks (subpart VVa).

3. Petition for Reconsideration

In addition to the final action under CAA section 111(b)(1)(B) described above, this action includes final amendments to the NSPS subparts VV and VVa (NSPS for VOC from equipment leaks in SOCMI) based on its reconsideration of certain aspects of these NSPS subparts that were raised in an administrative petition which the Agency granted pursuant to section 307(d)(7)(B) of the CAA. In January 2008, the EPA received one petition for reconsideration of the NSPS for VOC from equipment leaks in SOCMI (40 CFR part 60, subparts VV and VVa) and the NSPS for equipment leaks in petroleum refineries (40 CFR part 60, subparts GGG and GGGa) pursuant to CAA section 307(d)(7)(B) from the following petitioners: American Chemistry Council, American Petroleum Institute (API), and National Petrochemical and Refiners Association (now the American Fuel and Petrochemical Manufacturers). A copy of the petition and subsequent EPA correspondence granting reconsideration is provided in the docket for this rulemaking (see Docket No. EPA-HQ-OAR-2022-0730). The petitioners primarily requested that the EPA reconsider four provisions in those rules: (1) The clarification of the definition of process unit in subparts VV, VVa, GGG, and GGGa; (2) the assignment of shared storage vessels to specific process units in subparts VV, VVa, GGG, and GGGa; (3) the monitoring of connectors in subpart VVa; and (4) the definition of capital expenditure in subpart VVa. The rationale for this request is provided in the petition. The petitioners also requested that the EPA stay the effectiveness of these provisions of the rule pending resolution of their petition for reconsideration. On March 4, 2008, the EPA sent a letter to the petitioners informing them that the EPA was granting their request for reconsideration on issues (2) through (4) above. The letter also indicated that the EPA was not taking action on the first issue related to the definition of process unit. Finally, the letter indicated that the EPA was granting a 90-day stay of the provisions of the rules under reconsideration (see CAA section 307(d)(7)(B)), as well as the clarification of the definition of process unit, because of its reliance upon the new provision on the allocation of shared storage vessels. On June 2, 2008, the EPA published three actions in the Federal Register relative to extending the 90-day stay. Specifically, the EPA published a direct final rule (73 FR 31372) and a parallel proposal (73 FR 31416) in the Federal Register to extend the stay until we took final action on the issues of which the EPA granted reconsideration. Under the direct final rule, the stay would take effect 30 days after the close of the comment period on the proposed stay if no adverse comments were received. The third notice published that same day was an interim final rule extending the 90-day stay at the time for an additional 60 days so that the stay would not expire before the direct final rule could take effect (73 FR 31376). The EPA did not receive adverse comments on the proposed stay and, as a result, the stay became effective August 1, 2008.

In the three June 2, 2008 actions, the EPA indicated that it would be publishing a Federal Register notice in response to the petition; this action constitutes such notice and formally responds to the issues raised in the petition with respect to NSPS subparts VV and VVa. This final action presents the EPA's revisions to the NSPS for VOC from equipment leaks in SOCMI based on the EPA's reconsideration of issues (2) through (4) in the petition. We are also finalizing amendments that address the stay on issue (1) in the petition. See sections III.E and IV.E of this preamble for details about these final amendments.

B. What are the source categories and how did the previous standards regulate emissions?

The source categories that are the subject of this final action are the SOCMI source category subject to the HON and 11 Polymers and Resins Production source categories subject to the P&R I and P&R II NESHAP. This final action also addresses equipment leaks in the SOCMI and SOCMI air oxidation unit processes, distillation operations, and reactor processes. The NESHAP and NSPS included in this action that regulate emission sources from the SOCMI and Polymers and Resins Production source categories are described below.

1. HON

The sources affected by the HON include heat exchange systems and maintenance wastewater located at SOCMI facilities that are regulated under NESHAP subpart F; process vents, storage vessels, transfer racks, and wastewater streams located at SOCMI facilities that are regulated under NESHAP subpart G; equipment leaks associated with SOCMI processes regulated under NESHAP subpart H; and equipment leaks from certain non-SOCMI processes at chemical plants regulated under NESHAP subpart I. As previously mentioned, these four NESHAP are more commonly referred together as the HON.

In general, the HON applies to CMPUs that: (1) Produce one of the listed SOCMI chemicals, and (2) either use as a reactant or produce a listed organic HAP in the process. A CMPU means the equipment assembled and connected by pipes or ducts to process raw materials and to manufacture an intended product. A CMPU consists of more than one unit operation. A CMPU includes air oxidation reactors and their associated product separators and recovery devices; reactors and their associated product separators and recovery devices; distillation units and their associated distillate receivers and recovery devices; associated unit operations; associated recovery devices; and any feed, intermediate and product storage vessels, product transfer racks, and connected ducts and piping. A CMPU includes pumps, compressors, agitators, PRDs, sampling connection systems, open-ended valves or lines (OEL), valves, connectors, instrumentation systems, and control devices or systems. A CMPU is identified by its primary product.

a. NESHAP Subpart F

NESHAP subpart F contains provisions to determine which chemical manufacturing processes at a SOCMI facility are subject to the HON. Table 1 of NESHAP subpart F contains a list of SOCMI chemicals, and Table 2 of NESHAP subpart F contains a list of organic HAP regulated by the HON. In general, if a process both: (1) Produces one of the listed SOCMI chemicals and (2) either uses as a reactant or produces a listed organic HAP in the process, then that SOCMI process is subject to the HON. Details on how to determine which emission sources ( i.e., heat exchange systems, process vents, storage vessels, transfer racks, wastewater, and equipment leaks) are part of a chemical manufacturing process are also contained in NESHAP subpart F. NESHAP subpart F also contains monitoring requirements for HAP ( i.e., HAP listed in Table 4 of NESHAP subpart F) that may leak into cooling water from heat exchange systems. Additionally, NESHAP subpart F requires sources to prepare a description of procedures for managing maintenance wastewater as part of a SSM plan.

b. NESHAP Subpart G

NESHAP subpart G contains the standards for process vents, transfer racks, storage vessels, and wastewater at SOCMI facilities; it also includes emissions averaging provisions. NESHAP subpart G provides an equation representing a site-specific allowable overall emission limit for the combination of all emission sources subject to the HON at a SOCMI facility. Existing sources must demonstrate compliance using one of two approaches: the point-by-point compliance approach or the emissions averaging approach. New sources are not allowed to use emissions averaging, but rather must demonstrate compliance using the point-by-point approach. Under the point-by-point approach, the owner or operator would apply control to each Group 1 emission source. A Group 1 emission source is a point which meets the control applicability criteria, and the owner or operator must reduce emissions to specified levels; whereas a Group 2 emission source is one that does not meet the criteria and no additional emission reduction is required. Under the emissions averaging approach, an owner or operator may elect to control different groups of emission sources to different levels than specified by the point-by-point approach, as long as the overall emissions do not exceed the overall allowable emission level. For example, an owner or operator can choose not to control a Group 1 emission source (or to control the emission source with a less effective control technique) if the owner or operator over-controls another emission source. For the point-by-point approach, NESHAP subpart G contains the following standards:

• Group 1 process vents must reduce emissions of organic HAP using a flare meeting40 CFR 63.11(b); reduce emissions of total organic HAP or TOC by 98 percent by weight or to an exit concentration of 20 ppmv; or achieve and maintain a TRE index value greater than 1.0.

• Group 1 transfer racks must reduce emissions of total organic HAP by 98 percent by weight or to an exit concentration of 20 ppmv; or reduce emissions of organic HAP using a flare meeting 40 CFR 63.11(b), using a vapor balancing system, or by routing emissions to a fuel gas system or to a process.

• Group 1 storage vessels must reduce emissions of organic HAP using a fixed roof tank equipped with an IFR; using an external floating roof (EFR); using an EFR tank converted to a fixed roof tank equipped with an IFR; by routing emissions to a fuel gas system or to a process; or reduce emissions of organic HAP by 95 percent by weight using a closed vent system (i.e., vapor collection system) and control device, or combination of control devices (or reduce emissions of organic HAP by 90 percent by weight using a closed vent system and control device if the control device was installed before December 31, 1992).
• Group 1 process wastewater streams and equipment managing such streams at both new and existing sources must meet control requirements for: (1) Waste management units including wastewater tanks, surface impoundments, containers, individual drain systems, and oil-water separators; (2) treatment processes including the design steam stripper, biological treatment units, or other treatment devices; and (3) closed vent systems and control devices such as flares, catalytic incinerators,etc. Existing sources are not required to meet control requirements if Group 1 process wastewater streams are included in a 1 megagram per year source-wide exemption allowed by NESHAP subpart G.
• In general, Group 2 emission sources are not required to apply any additional emission controls (provided they remain below Group 1 thresholds); however, they are subject to certain monitoring, reporting, and recordkeeping requirements to ensure that they were correctly determined to be Group 2 and that they remain Group 2.

c. NESHAP Subpart H

NESHAP subpart H contains the standard for equipment leaks at SOCMI facilities, including leak detection and repair (LDAR) provisions and other control requirements. Equipment regulated includes pumps, compressors, agitators, PRDs, sampling connection systems, OEL, valves, connectors, surge control vessels, bottoms receivers, and instrumentation systems in organic HAP service. A piece of equipment is in organic HAP service if it contains or contacts a fluid that is at least 5 percent by weight organic HAP. Depending on the type of equipment, the standards require either periodic monitoring for and repair of leaks, the use of specified equipment to minimize leaks, or specified work practices. Monitoring for leaks must be conducted using EPA Method 21 in appendix A-7 to 40 CFR part 60 or other approved equivalent monitoring techniques.

d. NESHAP Subpart I

NESHAP subpart I provides the applicability criteria for certain non-SOCMI processes subject to the negotiated regulation for equipment leaks. Regulated equipment is the same as that for NESHAP subpart H.

2. P&R I NESHAP

The P&R I NESHAP generally follows and refers to the requirements of the HON, with additional requirements for batch process vents. Generally, the P&R I NESHAP applies to EPPUs and associated equipment. Similar to a CMPU in the HON, an EPPU means a collection of equipment assembled and connected by hard-piping or duct work used to process raw materials and manufacture elastomer product. The EPPU includes unit operations, recovery operations, process vents, storage vessels, and equipment that are covered by equipment leak standards and produce one of the elastomer types listed as an elastomer product, including: butyl rubber, epichlorohydrin elastomer, ethylene propylene rubber, halobutyl rubber, Hypalon^TM, neoprene, nitrile butadiene latex, nitrile butadiene rubber, polybutadiene rubber/styrene butadiene rubber by solution, polysulfide rubber, styrene butadiene latex, and styrene butadiene rubber by emulsion. An EPPU consists of more than one unit operation. An EPPU includes, as “equipment,” pumps, compressors, agitators, PRDs, sampling connection systems, OEL, valves, connectors, surge control vessels, bottoms receivers, instrumentation systems, and control devices or systems.

The emissions sources affected by the P&R I NESHAP include heat exchange systems and maintenance wastewater at P&R I facilities regulated under NESHAP subpart F; storage vessels, transfer racks, and wastewater streams at P&R I facilities regulated under NESHAP subpart G; and equipment leaks at P&R I facilities regulated under NESHAP subpart H. Process vents are also regulated emission sources but, unlike the HON, these emissions sources are subdivided into front and back-end process vents in the P&R I NESHAP. The front-end are unit operations prior to and including the stripping operations. These are further subdivided into continuous front-end process vents regulated under NESHAP subpart G and batch front-end process vents that are regulated according to the requirements within the P&R I NESHAP. Back-end unit operations include filtering, coagulation, blending, concentration, drying, separating, and other finishing operations, as well as latex and crumb storage. The requirements for back-end process vents are not subcategorized into batch or continuous and are also found within the P&R I NESHAP.

3. P&R II NESHAP

The P&R II NESHAP regulates HAP emissions from two source categories, Epoxy Resins Production (also referred to as BLR) and Non-Nylon Polyamides Production (also referred to as WSR). The P&R II NESHAP takes a different regulatory and format approach from the P&R I NESHAP but still refers to HON provisions for a portion of the standards. BLR are resins made by reacting epichlorohydrin and bisphenol A to form diglycidyl ether of bisphenol-A. WSR are polyamide/epichlorohydrin condensates which are used to increase the tensile strength of paper products.

The emission sources affected by the P&R II NESHAP are all HAP emission points within a facility related to the production of BLR or WSR. These emission points include process vents, storage tanks, wastewater systems, and equipment leaks. Equipment includes connectors, pumps, compressors, agitators, PRDs, sampling connection systems, OEL, and instrumentation system in organic HAP service. Equipment leaks are regulated under the HON ( i.e., NESHAP subpart H).

Process vents, storage tanks, and wastewater systems combined are regulated according to a production-based emission rate ( e.g., pounds HAP per million pounds BLR or WSR produced). For existing sources, the rate shall not exceed 130 pounds per 1 million pounds of BLR produced and 10 pounds per 1 million pounds of WSR produced. For new sources, BLR requires all uncontrolled emissions to achieve 98 percent reduction or limits the total emissions to 5,000 pounds of HAP per year. New WSR sources are limited to 7 pounds of HAP per 1 million pounds of WSR produced.

4. NSPS Subpart VVa

NSPS subpart VVa contains VOC standards for leaks from equipment within a process unit for which construction, reconstruction, or modification commenced after November 7, 2006. Under NSPS subpart VVa, equipment means each pump, compressor, PRD, sampling connection system, OEL, valve, and flange or other connector in VOC service and any devices or systems required by the NSPS. Process units consist of components assembled to produce, as intermediate or final products, one or more of the chemicals listed in 40 CFR 60.489. A process unit can operate independently if supplied with sufficient feed or raw materials and sufficient storage facilities for the product. The standards in NSPS subpart VVa include LDAR provisions and other control requirements. A piece of equipment is in VOC service if it contains or contacts a fluid that is at least 10 percent by weight VOC. Depending on the type of equipment, the standards require either periodic monitoring for and repair of leaks, the use of specified equipment to minimize leaks, or specified work practices. Monitoring for leaks must be conducted using EPA Method 21 in appendix A-7 to 40 CFR part 60 or other approved equivalent monitoring techniques.

5. NSPS Subpart III

NSPS subpart III regulates VOC emissions from SOCMI air oxidation reactors for which construction, reconstruction, or modification commenced after October 21, 1983. For the purpose of NSPS subpart III, air oxidation reactors are devices or process vessels in which one or more organic reactants are combined with air, or a combination of air and oxygen, to produce one or more organic compounds. The affected facility is designated as a single air oxidation reactor with its own individual recovery system (if any) or the combination of two or more air oxidation reactors and the common recovery system they share that produces one or more of the chemicals listed in 40 CFR 60.617 as a product, co-product, by-product, or intermediate. The BSER for reducing VOC emissions from SOCMI air oxidation units was identified as combustion ( e.g., incineration, flares) and the standard of performance requires owners and operators of an affected facility to reduce emissions of TOC (minus methane and ethane) by 98 percent by weight or to a concentration of 20 ppmv on a dry basis corrected to 3 percent oxygen; combust the emissions in a flare meeting 40 CFR 60.18(b); or maintain a TRE index value greater than 1.0 without use of VOC emission control devices.

6. NSPS Subpart NNN

NSPS subpart NNN regulates VOC emissions from SOCMI distillation operations for which construction, reconstruction, or modification commenced after December 30, 1983. For the purpose of NSPS subpart NNN, distillation operations are operations separating one or more feed stream(s) into two or more exit stream(s), each exit stream having component concentrations different from those in the feed stream(s); and the separation is achieved by the redistribution of the components between the liquid and vapor-phase as they approach equilibrium within a distillation unit. The affected facility is designated as a single distillation column with its own individual recovery system (if any) or the combination of two or more distillation columns and the common recovery system they share that is part of a process unit that produces any of the chemicals listed in 40 CFR 60.667 as a product, co-product, by-product, or intermediate. The BSER for reducing VOC emissions from SOCMI distillation operations was identified as combustion ( e.g., incineration, flares) and the standard of performance requires owners and operators of an affected facility to reduce emissions of TOC (minus methane and ethane) by 98 percent by weight or to a concentration of 20 ppmv on a dry basis corrected to 3 percent oxygen; combust the emissions in a flare meeting 40 CFR 60.18(b); or maintain a TRE index value greater than 1.0 without use of VOC emission control devices.

7. NSPS Subpart RRR

NSPS subpart RRR regulates VOC emissions from SOCMI reactor processes for which construction, reconstruction, or modification commenced after June 29, 1990. For the purpose of NSPS subpart RRR, reactor processes are unit operations in which one or more chemicals, or reactants other than air, are combined or decomposed in such a way that their molecular structures are altered and one or more new organic compounds are formed. The affected facility is designated as a single reactor process with its own individual recovery system (if any) or the combination of two or more reactor processes and the common recovery system they share that is part of a process unit that produces any of the chemicals listed in 40 CFR 60.707 as a product, co-product, by-product, or intermediate. The BSER for reducing VOC emissions from SOCMI reactor processes was identified as combustion ( e.g., incineration, flares) and the standard of performance requires owners and operators of an affected facility to reduce emissions of TOC (minus methane and ethane) by 98 percent by weight or to a concentration of 20 ppmv on a dry basis corrected to 3 percent oxygen; combust the emissions in a flare meeting 40 CFR 60.18(b); or maintain a TRE index value greater than 1.0 without use of VOC emission control devices.

C. What changes did we propose in our April 25, 2023, proposal?

1. NESHAP

a. Proposed Actions Related to CAA Section 112(f) Risk Assessment

To reduce risk from the SOCMI source category to an acceptable level, we proposed under CAA section 112(f) to require (in the HON) control of EtO emissions from: (1) Process vents, (2) storage vessels, (3) equipment leaks, (4) heat exchange systems, and (5) wastewater “in ethylene oxide service” (see 88 FR 25080, April 25, 2023, for our proposed definition of “in ethylene oxide service”). We also proposed requirements to reduce EtO emissions from maintenance vents, flares, and PRDs.

• For process vents and storage vessels in EtO service, we proposed owners and operators reduce emissions of EtO by either: (1) Venting emissions through a closed-vent system to a control device that reduces EtO by greater than or equal to 99.9 percent by weight, to a concentration less than 1 ppmv for each process vent and storage vessel, or to less than 5 lb/yr for all combined process vents; or (2) venting emissions through a closed-vent system to a flare meeting the proposed operating and monitoring requirements for flares in NESHAP subpart F.
• For equipment leaks in EtO service, we proposed the following combined requirements: monitoring of connectors in gas/vapor and light liquid service at a leak definition of 100 ppm on a monthly basis with no reduction in monitoring frequency and no delay of repair; light liquid pump monitoring at a leak definition of 500 ppm monthly; and gas/vapor and light liquid valve monitoring at a leak definition of 100 ppm monthly with no reduction in monitoring frequency and no delay of repair.
• For heat exchange systems in EtO service, we proposed to require owners or operators to conduct more frequent leak monitoring (weekly instead of quarterly) and repair leaks within 15 days from the sampling date (in lieu of the current 45-day repair requirement after receiving results of monitoring indicating a leak), and delay of repair would not be allowed.
• For wastewater in EtO service, we proposed to revise the Group 1 wastewater stream threshold for sources to include wastewater streams in EtO service.
• For maintenance vents, we proposed a requirement that owners and operators cannot release more than 1.0 ton of EtO from all maintenance vents combined in any consecutive 12-month period.
• For flares, we proposed a requirement that owners and operators can send no more than 20 tons of EtO to all of their flares combined from all HON emission sources at a facility in any consecutive 12-month period.
• For PRDs in EtO service, we proposed that any atmospheric PRD release is a violation of the standard.

To reduce risk from the Neoprene Production source category to an acceptable level, we proposed under CAA section 112(f) to require (in the P&R I NESHAP) control of chloroprene for: (1) Process vents, (2) storage vessels, and (3) wastewater “in chloroprene service” (see 88 FR 25080, April 25, 2023, for our proposed definition of “in chloroprene service”). We also proposed requirements to reduce chloroprene emissions from maintenance vents and PRDs.

• For process vents and storage vessels in chloroprene service, we proposed owners and operators reduce emissions of chloroprene by venting emissions through a closed-vent system to a control device that reduces chloroprene by greater than or equal to 99.9 percent by weight, to a concentration less than 1 ppmv for each process vent and storage vessel, or to less than 5 lb/yr for all combined process vents.
• For wastewater in chloroprene service, we proposed to revise the Group 1 wastewater stream threshold for sources to include wastewater streams in chloroprene service.
• For maintenance vents, we proposed a requirement that owners and operators cannot release more than 1.0 ton of chloroprene from all maintenance vents combined in any consecutive 12-month period.
• For PRDs in chloroprene service, we proposed that any atmospheric PRD release is a violation of the standard.
• We also proposed a facility-wide chloroprene emissions cap for all neoprene production emission sources as a backstop.

Based on our ample margin of safety analysis, we proposed that the controls to reduce EtO emissions at HON processes and chloroprene emissions at neoprene production processes to get risks to an acceptable level (described in this section of the preamble) would also provide an ample margin of safety to protect public health. We also proposed that HAP emissions from the source categories do not result in an adverse environmental effect, and that it is not necessary to set a more stringent standard to prevent, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect.

b. Proposed Actions Related to CAA Section 112(d)(6) Technology Review

Pursuant to the CAA section 112(d)(6) technology review for the HON and the P&R I, and P&R II NESHAP, we proposed that no revisions to the current standards beyond the fenceline monitoring work practice standard discussed below and those proposed under CAA section 112(f) are necessary for transfer racks, wastewater streams, and equipment leaks; however, we did propose additional changes under CAA section 112(d)(6) for heat exchange systems, storage vessels and process vents.

• For HON and P&R I heat exchange systems, we proposed requirements that owners or operators must use the Modified El Paso Method and repair leaks of total strippable hydrocarbon concentration (as methane) in the stripping gas of 6.2 ppmv or greater. The P&R II NESHAP currently does not regulate HAP emissions from heat exchange systems.
• For HON and P&R I storage vessels, we proposed to revise applicability thresholds to require existing storage vessels between 38 m³ (10,000 gal) and 151 m³ (40,000 gal) with a vapor pressure ≥6.9 kilopascals to add control, and also require upgraded deck fittings and controls for guidepoles for all IFR storage vessels. For P&R II storage vessels, we proposed that no revisions to the current standards are necessary.
• For HON and P&R I process vents, we proposed to: (1) Remove the TRE concept in its entirety; (2) remove 50 ppmv and 0.005 scmm Group 1 process vent thresholds; and (3) redefine a Group 1 process vent (require control) as any process vent that emits ≥1.0 lb/hr of total organic HAP. For P&R II process vents, we proposed that no revisions to the current standards are necessary.

Under CAA section 112(d)(6), we also proposed a fenceline monitoring work practice standard requiring owners and operators to monitor for any of six specific HAP ( i.e., benzene, 1,3-butadiene, ethylene dichloride, vinyl chloride, EtO, and chloroprene) if their site uses, produces, stores, or emits any of them, and conduct root cause analysis and corrective action upon exceeding the annual average concentration action level set forth for each HAP. We also requested public comments on whether to promulgate the fenceline monitoring work practice standards, including the proposed action levels for EtO and chloroprene, under the second step of the CAA section 112(f)(2) residual risk decision framework to provide an ample margin of safety to protect public health in light of facility-wide risks.

c. Proposed Actions Related to CAA Section 112(d)(2) and (3), and 112(h)

We proposed other requirements for the HON and P&R I and P&R II NESHAP based on analyses performed pursuant to CAA sections 112(d)(2) and (3), and 112(h), and that are consistent with Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008), ensuring that CAA section 112 standards apply continuously, including:

• new monitoring and operational requirements for flares in the HON and P&R I NESHAP;
• work practice standards for periods of SSM for certain HON and P&R I vent streams (i.e., PRD releases, maintenance vents, and planned routine maintenance of storage vessels);
• regulatory provisions for vent control bypasses for certain HON and P&R I vent streams (i.e., closed vent systems containing bypass lines);
• dioxins and furans emission limits in the HON and the P&R I and P&R II NESHAP;
• new monitoring requirements for HON and P&R I pressure vessels;
• new emission standards for HON & P&R I surge control vessels and bottoms receivers;
• a revised applicability threshold for HON transfer racks;
• requirements in the P&R II NESHAP for heat exchange systems;
• requirements in the P&R II NESHAP for WSR sources and equipment leaks;
• to require owners and operators that use a sweep, purge, or inert blanket between the IFR and fixed roof of a storage vessel to route emissions through a closed vent system and control device;
• to remove exemptions in the HON and the P&R I and P&R II NESHAP from the requirement to comply during periods of SSM; and
• to remove affirmative defense provisions from the P&R I NESHAP that were adopted in 2011.

d. Other Proposed Actions

In addition to the actions described in the sections above related to NESHAP, we also proposed:

• changes to the HON and the P&R I and P&R II NESHAP recordkeeping and reporting requirements to require the use of electronic reporting of performance test reports and periodic reports;
• restructuring of all HON definitions;
• monitoring requirements for adsorbers that cannot be regenerated and regenerative adsorbers that are regenerated offsite;
• to require subsequent performance testing on non-flare control devices no later than 60 calendar months after the previous performance test; and
• to correct section reference errors and make other minor editorial revisions.

2. NSPS

a. Proposed Actions Related to CAA Section 111(b)(1)(B) Review

Pursuant to the CAA section 111(b)(1)(B) reviews for the SOCMI NSPS rules, we proposed new NSPS for equipment leaks (NSPS subpart VVb) and process vents associated with air oxidation units (NSPS subpart IIIa), distillation operations (NSPS subpart NNNa), and reactor processes (NSPS subpart RRRa).

• For NSPS subpart VVb, we proposed the same requirements in NSPS subpart VVa plus a requirement that all gas/vapor and light liquid valves be monitored monthly at a leak definition of 100 ppm and all connectors be monitored once every 12 months at a leak definition of 500 ppm.
• For NSPS subparts IIIa, NNNa, and RRRa, we proposed the same requirements in NSPS subparts III, NNN, and RRR, except we proposed to: (1) Eliminate the TRE concept in its entirety (including the removal of the alternative of maintaining a TRE index value greater than 1 without the use of control device and the limited applicability exemptions) and instead require owners and operators to reduce emissions of TOC (minus methane and ethane) from all vent streams of an affected facility (i.e., SOCMI air oxidation unit processes, distillation operations, and reactor processes for which construction, reconstruction, or modification commences after April 25, 2023) by 98 percent by weight or to a concentration of 20 ppmv on a dry basis corrected to 3 percent oxygen, or combust the emissions in a flare meeting the same operating and monitoring requirements for flares that we proposed for flares subject to the HON; (2) eliminate the relief valve discharge exemption from the definition of “vent stream” such that any relief valve discharge to the atmosphere of a vent stream is a violation of the emissions standard; (3) require the same work practice standards for maintenance vents that we proposed for HON process vents; and (4) require the same monitoring requirements that we proposed for HON process vents for adsorbers that cannot be regenerated and regenerative adsorbers that are regenerated offsite.

b. Proposed Actions Related to NSPS Subparts VV and VVa Reconsideration

In response to the January 2008 petition for reconsideration we proposed: (1) Definitions for “process unit” for NSPS subparts VV and VVa; (2) to remove the requirements in 40 CFR 60.482-1(g) (for NSPS subpart VV) and 40 CFR 60.482-1a(g) (for NSPS subpart VVa) that are related to a method for assigning shared storage vessels to specific process units; (3) to remove the connector monitoring provisions from NSPS subpart VVa at 40 CFR 60.482-11a in their entirety and instead, include connector monitoring provisions in NSPS subpart VVb; and (4) to revise the “capital expenditure” definition in NSPS subpart VVa at 40 CFR 60.481a to reflect the definition used in NSPS subpart VV at 40 CFR 60.481 for owners or operators that start a new, reconstructed, or modified affected source prior to November 16, 2007.

c. Other Proposed Actions

In addition to the actions described in the sections above related to the CAA section 111(b)(1)(B) reviews for the SOCMI NSPS rules and the NSPS subparts VV and VVa reconsideration, we also proposed:

• standards in NSPS subparts VVb, IIIa, NNNa, and RRRa that apply at all times;
• the use of electronic reporting of performance test reports and periodic reports;
• several corrections to the calibration drift assessment requirements in NSPS subpart VVa; and
• to require subsequent performance testing on non-flare control devices no later than 60 calendar months after the previous performance test.

III. What is included in this final rule?

This action finalizes the EPA's determinations pursuant to the applicable provisions of CAA section 112 for the SOCMI source category and various polymers and resins source categories and amends the HON and P&R I and P&R II NESHAP based on those determinations. In addition, this action finalizes determinations of our review of the SOCMI NSPS rules pursuant to CAA section 111(b)(1)(B). This actions also finalizes other changes to the NESHAP, including adding requirements and clarifications for periods of SSM and bypasses; revising the operating and monitoring requirements for flares; adding provisions for electronic reporting; and other editorial and technical changes. Additionally, this action finalizes amendments to NSPS subparts VV and VVa in response to the January 2008 petition for reconsideration. This action also reflects several changes to the April 25, 2023 proposal (88 FR 25080), in consideration of comments received during the public comment period as described in section IV of this preamble.

A. What are the final rule amendments based on the risk review for the SOCMI and Neoprene Production source categories NESHAP?

Consistent with the proposal, the EPA determined that the risks for the SOCMI and Neoprene Production source categories under the previous MACT standards are unacceptable. When risks are unacceptable, the EPA must determine the emissions standards necessary to reduce risk to an acceptable level. As such, the EPA is promulgating final amendments to the HON pursuant to CAA section 112(f)(2) that require control of EtO for: (1) Process vents, (2) storage vessels, (3) equipment leaks, (4) heat exchange systems, and (5) wastewater “in ethylene oxide service.” We are also finalizing requirements to reduce EtO emissions from maintenance vents and PRDs. As discussed in section IV.A of this preamble, implementation of these controls will reduce risk to an acceptable level and provide an ample margin of safety to protect public health from source category emissions points. In addition, the fenceline monitoring requirements being finalized in this action will further reduce whole-facility EtO and chloroprene emissions at facilities with HON and Neoprene Production processes, with consequential reductions in risks from these pollutants. In general, we are finalizing all of the EtO related requirements as proposed (for HON), except: we are not finalizing (in response to persuasive comments received during the public comment period) the proposed requirement at 40 CFR 63.108(p) that would prohibit owners and operators from sending more than 20 tons of EtO to all of their flares combined in any consecutive 12-month period. In addition to the primary CAA section 112(d)(6)-based fenceline monitoring program action levels that we are finalizing for all six HAP that reflect compliance with the source category-specific emissions limits for SOCMI and P&R I source category processes (see section III.B.1 of this preamble), we are also finalizing separately, in the P&R I NESHAP for Neoprene Production sources, an additional secondary action level under CAA section 112(f)(2) for fenceline monitoring of chloroprene emissions. This secondary action level for chloroprene for facilities with Neoprene Production sources is the same action level that was proposed. The primary chloroprene action level, which applies to sources subject to 40 CFR subpart H in the HON, is higher than what was proposed, but reflects the modeled emissions concentrations expected to result from compliance with the other emission standards adopted in the final rule, as we discussed in the proposed rule. See 88 FR at 25145/col. 2. The secondary chloroprene action level will further reduce whole-facility risks caused by such emissions from facilities with Neoprene Production sources, consistent with the goal to provide an ample margin of safety to protect public health. For this reason, for facilities with Neoprene Production sources we are promulgating the secondary chloroprene action level we had proposed under CAA section 112(d)(6) under our CAA section 112(f)(2) authority, as we requested comment on in the proposed rule. See id., at 25145/col. 3.

Also, based on comments received on the proposed rulemaking, we are clarifying in this final action that:

• we mean “the procedures specified in § 63.109” instead of “sampling and analysis” within the definitions of “in ethylene oxide service” for storage vessels, equipment leaks, and heat exchange systems (see40 CFR 63.101);
• the sampling site for determining whether an emissions source is in EtO service is after the last recovery device (if any recovery devices are present) but prior to the inlet of any control device that is present and prior to release to the atmosphere (see40 CFR 63.109(a));
• owners and operators can use good engineering judgment to determine the percent of EtO of the process fluid cooled by the heat exchange system similar to what we are allowing for equipment leaks in40 CFR 63.109(c)(2) (see 40 CFR 63.109(e));
• the 5 lb/yr EtO mass threshold for combined process vents in EtO service is on a CMPU-by-CMPU basis (see40 CFR 63.113(j)(2), 40 CFR 63.124(a)(4) and (a)(4)(iii), and within the definition of “in ethylene oxide service” for process vents);
• owners and operators may delay repair of equipment leaks in EtO service, and heat exchange systems in EtO service, indefinitely as long as there is no longer an active EtO leak once the equipment is isolated and not in EtO service (see40 CFR 63.104(h)(6) and 40 CFR 63.171(b));
• we mean “process wastewater” instead of “wastewater” in40 CFR 63.132(c)(1)(iii) and (d)(1)(ii);
• owners and operators can demonstrate compliance with the standards for wastewater in EtO service if the concentration of EtO is reduced, by removal or destruction, to a level less than 1 ppmw as determined in the procedures specified in40 CFR 63.145(b) (see 40 CFR 63.138(b)(3) and (c)(3)); and
• owners and operators can use test methods specified in40 CFR 63.109(d) for analysis of EtO in wastewater (see 40 CFR 63.144(b)(5)(i)).

Additionally, the EPA is promulgating final amendments to the P&R I NESHAP for Neoprene Production sources pursuant to CAA section 112(f)(2) that require control of chloroprene for: (1) Process vents, (2) storage vessels, (3) wastewater “in chloroprene service.” We are also finalizing requirements to reduce chloroprene emissions from maintenance vents and PRDs. As discussed in section IV.A of this preamble, implementation of these controls will reduce risk to an acceptable level and provide an ample margin of safety to protect public health from the Neoprene Production source category. In general, we are finalizing all of the chloroprene related requirements as proposed (for Neoprene Production sources in the P&R I NESHAP), except in response to persuasive comments received during the public comment period: (1) We are not finalizing the facility-wide chloroprene emissions cap at 40 CFR 63.483(a)(10) that would prohibit owners and operators from emitting 3.8 tpy of chloroprene in any consecutive 12-month period from all neoprene production emission sources; (2) we are revising the performance standard from a 99.9 percent by weight reduction requirement to a 98 percent by weight reduction requirement for storage vessels in chloroprene service (see 40 CFR 63.484(u) and 40 CFR 53.510), continuous front-end process vents in chloroprene service (see 40 CFR 63.485(y) and 40 CFR 53.510), and batch front-end process vents in chloroprene service (see 40 CFR 63.487(j)); (3) we are finalizing a requirement that owners and operators reduce emissions of chloroprene from back-end process vents in chloroprene service at affected sources producing neoprene by venting emissions through a closed-vent system to a non-flare control device that reduces chloroprene by greater than or equal to 98 percent by weight, to a concentration less than 1 ppmv for each process vent, or to less than 5 lb/yr for all combined process vents (see 40 CFR 63.494(a)(7)); and (4) we are finalizing in the primary CAA section 112(d)(6)-based fenceline monitoring program action levels for all six HAP addressed in the proposal that reflect compliance with the source category-specific emissions limits for SOCMI and P&R I source category processes, and which subject sources are largely already meeting (see section III.B.1 of this preamble). Separately, we are also setting an additional secondary action level under CAA section 112(f)(2) for fenceline monitoring of chloroprene emissions. This standard will further reduce whole-facility risks caused by such emissions, consistent with the goal to provide an ample margin of safety to protect public health. Also, based on comments received on the proposed rulemaking, we are clarifying in this final action that:

• we mean “the procedures specified in § 63.509” instead of “sampling and analysis” within the definitions of “in chloroprene service” for storage vessels (see40 CFR 63.482);
• the sampling site for determining whether an emissions source is in chloroprene service is after the last recovery device (if any recovery devices are present) but prior to the inlet of any control device that is present and prior to release to the atmosphere (see40 CFR 63.509(a)); and
• the 5 lb/yr chloroprene mass threshold for combined process vents in chloroprene service is on a EPPU-by-EPPU basis (see the definition of “in chloroprene service” for process vents).

Section IV.A.3 of this preamble provides a summary of key comments we received on the CAA section 112(f) provisions and our responses.

B. What are the final rule amendments based on the technology review for the SOCMI, P&R I, and P&R II source categories NESHAP pursuant to CAA section 112(d)(6) and NSPS reviews for the SOCMI source category pursuant to CAA section 111(b)(1)(B)?

1. NESHAP

For transfer racks, wastewater streams, and equipment leaks in the SOCMI, P&R I, and P&R II source categories, the EPA is finalizing its proposed determination in the technology review that there are no developments in practices, processes, and control technologies that warrant revisions to the MACT standards beyond those needed under CAA section 112(f) or for other purposes besides section 112(d)(6). Therefore, with the exception of the fenceline monitoring standards that are discussed further below, we are not finalizing revisions to the MACT standards for these emission sources under CAA section 112(d)(6).

For heat exchange systems, we determined that there are developments in practices, processes, and control technologies that warrant revisions to the MACT standards for heat exchange systems in the SOCMI, P&R I, and P&R II source categories. Therefore, to satisfy the requirements of CAA section 112(d)(6), we are revising the MACT standards, consistent with the proposed rule (88 FR 25080, April 25, 2023), to include revisions to the heat exchange system requirements to require owners or operators to use the Modified El Paso Method and repair leaks of total strippable hydrocarbon concentration (as methane) in the stripping gas of 6.2 ppmv or greater. We are also finalizing, as proposed, that owners and operators may use the current leak monitoring requirements for heat exchange systems at 40 CFR 63.104(b) in lieu of using the Modified El Paso Method provided that 99 percent by weight or more of the organic compounds that could leak into the heat exchange system are water soluble and have a Henry's Law Constant less than 5.0E-6 atmospheres-cubic meters/mol at 25 degrees Celsius. See 40 CFR 63.104(g) through (j) and (l) (for HON), 40 CFR 63.502(n)(7) (for the P&R I NESHAP), and 40 CFR 63.523(d) and 40 CFR 63.524(c) (for the P&R II NESHAP).

For storage vessels, we did not identify any control options for storage tanks subject to the P&R II NESHAP. However, we determined that there are developments in practices, processes, and control technologies that warrant revisions to the MACT standards for storage vessels in the SOCMI and P&R I source categories. Therefore, to satisfy the requirements of CAA section 112(d)(6), we are revising the MACT standards, consistent with the proposed rule (88 FR 25080, April 25, 2023), to include revisions to the storage vessel applicability threshold to require both existing and new storage vessels between 38 m³ and 151 m³ with a vapor pressure greater than or equal to 6.9 kilopascals to reduce emissions of organic HAP by 95 percent utilizing a closed vent system and control device, or reduce organic HAP emissions either by utilizing an IFR, an EFR, or by routing the emissions to a process or a fuel gas system, or vapor balancing. We are also finalizing, as proposed, requirements that all openings in an IFR (except those for automatic bleeder vents (vacuum breaker vents), rim space vents, leg sleeves, and deck drains) be equipped with a deck cover; and that the deck cover be equipped with a gasket between the cover and the deck; and control requirements for guidepoles for all storage vessels equipped with an IFR. See Tables 5 and 6 to subpart G, and 40 CFR 63.119(b)(5)(ix), (x), (xi), and (xii) (for HON) and 40 CFR 63.484(t) (for the P&R I NESHAP).

For process vents, we did not identify any control options for process vents subject to the P&R II NESHAP. However, we determined that there are developments in practices, processes, and control technologies that warrant revisions to the MACT standards for process vents in the SOCMI and P&R I source categories. Therefore, to satisfy the requirements of CAA section 112(d)(6), we are revising the MACT standards, consistent with the proposed rule (88 FR 25080, April 25, 2023), to include revisions to the process vent applicability threshold to redefine a HON Group 1 process vent and P&R I Group 1 continuous front-end process vent ( i.e., to require control) as any process vent that emits greater than or equal to 1.0 lb/hr of total organic HAP. We are also removing, as proposed, the TRE concept in its entirety, and removing, as proposed, the 50 ppmv and 0.005 scmm Group 1 process vent thresholds. See 40 CFR 63.101 and 40 CFR 63.113(a)(1), (2), and (4) (for HON) and 40 CFR 63.482 and 40 CFR 63.485(l)(6), (o)(6), (p)(5), and (x) (for the P&R I NESHAP). To satisfy the requirements of CAA section 112(d)(6), we are also revising the MACT standards, consistent with the proposed rule (88 FR 25080, April 25, 2023), to include revisions to the process vent applicability threshold to redefine a P&R I Group 1 batch front-end process vent as process vents that release total annual organic HAP emissions greater than or equal to 4,536 kg/yr (10,000 lb/yr) from all batch front-end process vents combined. See 40 CFR 63.482, 40 CFR 63.487(e)(1)(iv), 40 CFR 63.488(d)(2), (e)(4), (f)(2), and (g)(3) (for the P&R I NESHAP).

Also, to satisfy the requirements of CAA section 112(d)(6), we are revising the MACT standards, consistent with the proposed rule (88 FR 25080, April 25, 2023), to include a fenceline monitoring work practice standard for the SOCMI and P&R I source categories, requiring owners and operators to monitor for any of six specific HAP ( i.e., benzene, 1,3-butadiene, ethylene dichloride, vinyl chloride, EtO, and chloroprene) if their affected source uses, produces, stores, or emits any of them, and to conduct root cause analysis and corrective action upon exceeding the annual average concentration action level set forth for each HAP. However, based on comments received on the proposed rulemaking, we are amending the fenceline monitoring work practice standards in the final rule adopted under CAA section 112(d)(6) to include the action level of 0.8 ug/m for chloroprene, which reflects compliance with the source category-specific emissions limits for P&R I source category processes. The action levels for benzene, 1,3-butadiene, ethylene dichloride, EtO, and vinyl chloride will also correspond to the modeled concentrations resulting from compliance with the process emission standards promulgated in the final rule and/or levels that HON-subject sources are largely already meeting. Separately, we are also setting an additional secondary action level of 0.3 ug/m for chloroprene under CAA section 112(f)(2), because this standard will further reduce elevated risks from facility-wide emissions of this pollutant consistent with the goal to provide an ample margin of safety to protect public health. See 40 CFR 63.184 (for HON) and 40 CFR 63.502 (for the P&R I NESHAP). In addition, the final rule includes burden reduction measures to allow owners and operators to skip fenceline measurement periods for specific monitors with a history of measurements that are at or below certain specified action levels. We have also made a clarification that fenceline monitoring is required for owners and operators with affected sources that produce, store, or emit one or more of the target analytes; and we have reduced the requirements in the final rule for the minimum detection limit of alternative measurement approaches (for fenceline monitoring). In addition, we have made clarifications on the calculation of delta c (Δc) when a site-specific monitoring plan is used to correct monitoring location concentrations due to offsite impacts, and we have made a change in the required method detection limit for alternative test methods from an order of magnitude below the action level to one-third of the action level. Finally, with the exception of fenceline monitoring of chloroprene at P&R I affected sources producing neoprene, discussed below, we have changed the compliance date to begin fenceline monitoring from 1 to 2 years after the effective date of the final rule. For P&R I affected sources producing neoprene, we have changed the compliance date for fenceline monitoring of chloroprene to begin no later than October 15, 2024, or upon startup, whichever is later, subject to the owner or operator seeking the EPA's authorization of an extension of up to 2 years from July 15, 2024.

Section III.G.1 of this preamble provides a more detailed discussion of the effective and compliance dates for the requirements we are finalizing in this action for the HON and the P&R I NESHAP. Section IV.B.3 of this preamble provides a summary of key comments we received on the CAA section 112(d)(6) provisions and our responses.

2. NSPS

The EPA is finalizing, as proposed, a determination that the BSER for reducing VOC emissions from SOCMI air oxidation units, distillation operations, and reactor processes remains combustion ( e.g., incineration, flares), and we are also maintaining that the standard of performance of 98 percent reduction of TOC (minus methane and ethane), or reduction of TOC (minus methane and ethane) to an outlet concentration of 20 ppmv on a dry basis corrected to 3 percent oxygen, continues to reflect the BSER for NSPS subparts IIIa, NNNa, and RRRa. While we are finalizing no changes in the BSER for reducing VOC emissions from SOCMI air oxidation units, distillation operations, and reactor processes, we determined that there are certain advances in process operations that were not identified or considered during development of the original NSPS subparts III, NNN, and RRR (for SOCMI air oxidation units, distillation operations, and reactor processes, respectively), which warrant revisions to the requirements for process vents in the SOCMI source category. Therefore, pursuant to CAA section 111(b)(1)(B), we are finalizing revised process vent requirements in new NSPS subparts IIIa, NNNa, and RRRa (for SOCMI air oxidation unit processes, distillation operations, and reactor processes for which construction, reconstruction, or modification commenced after April 25, 2023), consistent with the proposed rule (88 FR 25080, April 25, 2023). In particular, we are finalizing for NSPS subparts IIIa, NNNa and RRRa, as proposed, the removal of the entire TRE concept (including the removal of the alternative of maintaining a TRE index value greater than 1 without the use of control device and the limited applicability exemptions) such that owners and operators of affected facilities (for which construction, reconstruction, or modification commences after April 25, 2023) are required to reduce emissions of TOC (minus methane and ethane) from all vent streams of an affected facility by 98 percent by weight or to a concentration of 20 ppmv on a dry basis corrected to 3 percent oxygen, or combust the emissions in a flare. The EPA is also finalizing, as proposed, that affected sources that combust the emissions in a flare meet the same operating and monitoring requirements for flares that we are finalizing for flares subject to the HON. However, based on comments received on the proposed rulemaking, we are finalizing a mass-based exemption criteria of 0.001 lb/hr TOC (for which emission controls are not required) in new NSPS subparts IIIa and NNNa. Also, as proposed, we are not including in the final NSPS subparts IIIa, NNNa, and RRRa a relief valve discharge exemption in the definition of “vent stream”; instead, any relief valve discharge to the atmosphere of a vent stream is a violation of the emissions standard. In addition, we are finalizing, as proposed, the same work practice standards for maintenance vents that we are finalizing for HON process vents, and, as proposed, the same monitoring requirements that we are finalizing for HON process vents for adsorbers that cannot be regenerated and regenerative adsorbers that are regenerated offsite.

For equipment leaks, we determined that there are techniques used in practice related to LDAR of certain equipment that achieve greater emission reductions than those currently required by NSPS subpart VVa. Therefore, pursuant to the requirements of CAA section 111(b)(1)(B), we are finalizing revised equipment leak requirements in new NSPS subpart VVb (for facilities that commence construction, reconstruction, or modification after April 25, 2023), consistent with the proposed rule (88 FR 25080, April 25, 2023). We are finalizing that BSER for gas and light liquid valves is the same monitoring in an LDAR program as NSPS subpart VVa, but now at a leak definition of 100 ppm, and BSER for connectors is monitoring in the LDAR program at a leak definition of 500 ppm and monitored annually, with reduced frequency for good performance. In a change from the proposed rule, we are finalizing a definition of “capital expenditure” in NSPS subpart VVb to use a formula that better reflects the trajectory of inflation.

Section IV.B.3 of this preamble provides a summary of key comments we received on the proposed provisions pursuant to CAA section 111(b)(1)(B) and our responses.

C. What are the final rule amendments pursuant to CAA sections 112(d)(2) and (3), and 112(h) for the SOCMI, P&R I, and P&R II source categories?

Consistent with Sierra Club v. EPA 551 F. 3d 1019 (D.C. Cir. 2008) and the April 25, 2023, proposal (88 FR 25080), we are revising monitoring and operational requirements for flares to ensure HON and P&R I flares meet the MACT standards at all times when controlling HAP emissions. See 40 CFR 63.108 (for HON) and 40 CFR 63.508 (for the P&R I NESHAP). In addition, we are finalizing provisions and clarifications as proposed for periods of SSM and bypasses, including:

• PRD releases (see40 CFR 63.165(e) (for HON) and 40 CFR 63.502(a) (for the P&R I NESHAP));
• bypass lines on closed vent systems (see40 CFR 63.114(d)(3), 40 CFR 63.118(a)(5), 40 CFR 63.127(d)(3), 40 CFR 63.130(a)(2)(iv), (b)(3), and (d)(7), and 40 CFR 63.148(f)(4), (i)(3)(iii), and (j)(4) (for HON and the P&R I NESHAP) as well as 40 CFR 63.480(d)(3), 40 CFR 63.491(e)(6), 40 CFR 63.497(d)(3), and 63.498(d)(5)(v) (for the P&R I NESHAP));
• maintenance vents and equipment openings (excluding storage vessel degassing) (see40 CFR 63.113(k) (for HON) 40 CFR 63.485(x) and 40 CFR 63.487(i) (for the P&R I NESHAP));
• storage vessel degassing (see40 CFR 63.119(a)(2) (for HON) and 40 CFR 63.484(a) (for the P&R I NESHAP)); and
• planned routine maintenance for storage vessels (see40 CFR 63.119(e)(3) through (5) (for HON) and 40 CFR 63.484(a) (for the P&R I NESHAP)).

However, in response to comments received on the proposed rulemaking for storage vessel degassing, we are: (1) Clarifying in the final rule at 40 CFR 63.119(a)(6) that the storage vessel degassing work practice standard applies to all Group 1 storage vessels, including storage vessels in EtO service, and (2) revising the storage vessel degassing work practice standard in the final rule at 40 CFR 63.119(a)(6) to allow storage vessels to be vented to the atmosphere once a storage vessel degassing organic HAP concentration of 5,000 ppmv as methane is met, or until the vapor space concentration is less than 10 percent of the LEL. In addition, in response to comments received on the proposed rulemaking for planned routine maintenance of storage vessels, we are clarifying in the final rule at 40 CFR 63.119(f)(3) that the 240-hour planned routine maintenance provisions also apply for breathing losses for fixed rood roof vessels routed to a fuel gas system or to a process.

To address regulatory gaps, we are also finalizing the emission limits as proposed for polychlorinated dibenzo-p-dioxins (dioxins) and polychlorinated dibenzofurans (furans) for HON, P&R I, and P&R II facilities (see 40 CFR 63.113(a)(5) (for HON), 40 CFR 63.485(x) and 40 CFR 63.487(a)(3) and (b)(3) (for the P&R I NESHAP), and 40 CFR 63.523(e), 40 CFR 63.524(a)(3), and 40 CFR 63.524(b)(3) (for the P&R II NESHAP)). We are also finalizing the requirements as proposed for transfer operations (see 40 CFR 63.101 (for HON)), heat exchange systems (40 CFR 63.523(d) and 40 CFR 63.524(c) (for the P&R II NESHAP)), and WSR sources and equipment leaks (see 40 CFR 63.524(a)(3) and (b)(3) (for the P&R II NESHAP)). In addition, we are finalizing the requirements as proposed for pressure vessels (see 40 CFR 63.119(a)(7) (for HON) and 40 CFR 63.484(t) (for the P&R I NESHAP)), surge control and bottoms receivers (see 40 CFR 63.170(b) (for HON) and 40 CFR 63.485(d) (for the P&R I NESHAP)), but with a few changes in the final rule in response to persuasive comments received during the public comment period.

In response to comments received on the proposed rulemaking for pressure vessels, we are:

• clarifying that the pressure vessel requirements at40 CFR 63.119(a)(7) only apply to pressure vessels that are considered Group 1 storage vessels;
• clarifying that if the equipment is not a connector, gas/vapor or light liquid valve, light liquid pump, or PRD in ETO service and the equipment is on a pressure vessel located at a HON or P&R I facility, then that particular equipment is not subject to HON subpart H, but rather the equipment is subject to the pressure vessel requirements we proposed and are finalizing in40 CFR 63.119(a)(7);
• clarifying that unsafe and difficult/inaccessible to monitor provisions in40 CFR 63.168(h) and (i) (for valves in gas/vapor service and in light liquid service) and in 40 CFR 63.174(f) and (h) (for connectors in gas/vapor service and in light liquid service) still apply to valves and connectors when complying with 40 CFR 63.119(a)(7); and
• replacing the word “deviation” with “violation” in the final rule text at40 CFR 63.119(a)(7).

In response to comments received on the proposed rulemaking for surge control and bottoms receivers, we are adding language in the “C” and “Q” terms of the equations at 40 CFR 63.115(g)(3)(ii) and (g)(4)(iv) to allow the use of engineering calculations to determine concentration or flow rate only in situations where measurements cannot be taken with EPA reference methods. We are also adding reference methods for measuring flow rate at 40 CFR 63.115(g)(3)(ii) and 40 CFR 63.115(g)(4)(iv).

Finally, we are finalizing, as proposed, that owners and operators that use a sweep, purge, or inert blanket between the IFR and fixed roof of a storage vessel are required to route emissions through a closed vent system and control device (see 40 CFR 63.119(b)(7)). However, based on comments received on the proposed rulemaking, we are clarifying in the final rule that 40 CFR 63.119(b)(7) applies only if a continuous sweep, purge, or inert blanket is used between the IFR and fixed roof that causes a pressure/vacuum vent to remain continuously open to the atmosphere where uncontrolled emissions are greater than or equal to 1.0 lb/hr of total organic HAP.

Section IV.C.3 of this preamble provides a summary of key comments we received on the CAA sections 112(d)(2), (d)(3), and (h) provisions and our responses.

D. What are the final rule amendments addressing emissions during periods of SSM?

1. NESHAP

We are finalizing the proposed amendments to the HON and the P&R I and P&R II NESHAP to remove and revise provisions related to SSM. In its 2008 decision in Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008), the Court vacated portions of two provisions in the EPA's CAA section 112 regulations governing the emissions of HAP during periods of SSM. Specifically, the Court vacated the SSM exemptions contained in 40 CFR 63.6(f)(1) and (h)(1), holding that under section 302(k) of the CAA, emissions standards or limitations must be continuous in nature, and that the SSM exemptions violated the CAA's requirement that some CAA section 112 standards apply at all times. We are finalizing, as proposed, a requirement that the standards apply at all times (see 40 CFR 63.102(e) (for HON) and 40 CFR.525(j) (for the P&R II NESHAP)), consistent with the Sierra Club decision. We determined that facilities in the SOCMI and P&R II source categories can meet the applicable MACT standards at all times, including periods of startup and shutdown. We note that on April 21, 2011 (see 77 FR 22566), the EPA finalized amendments to eliminate the SSM exemption in the P&R I NESHAP; however, for consistency with the SSM-related amendments that we are finalizing for the HON and the P&R II NESHAP, we are also finalizing, as proposed, additional amendments to the P&R I NESHAP related to the SSM exemption that were not addressed in the April 21, 2011, P&R I rule.

As discussed in the proposal preamble, the EPA interprets CAA section 112 as not requiring emissions that occur during periods of malfunction to be factored into development of CAA section 112 standards, although the EPA has the discretion to set standards for malfunction periods where feasible. Where appropriate, and as discussed in section III.C of this preamble, we are also finalizing alternative standards for certain emission points during periods of SSM to ensure a CAA section 112 standard applies “at all times.” Other than for those specific emission points discussed in section III.C of this preamble, the EPA determined that no additional standards are needed to address emissions during periods of SSM and that facilities in the SOCMI and P&R II source categories can meet the applicable MACT standards at all times, including periods of startup and shutdown.

We are also finalizing, as proposed, revisions to the HON and P&R II General Provisions tables (Table 3 to subpart F of part 63 and Table 1 to subpart W of part 63, respectively) to eliminate requirements that include rule language providing an exemption for periods of SSM. We note that the EPA already made a similar revision to the General Provisions table to the P&R I NESHAP (see 77 FR 22566, April 21, 2011). Additionally, we are finalizing our proposal to eliminate language related to SSM that treats periods of startup and shutdown the same as periods of malfunction. Finally, we are finalizing our proposal to revise reporting and recordkeeping requirements for deviations as they relate to exemptions for periods of SSM. These revisions are consistent with the requirement in 40 CFR 63.102(e) and 40 CFR.525(j) that the standards apply at all times. We are also finalizing, as proposed, a revision to the performance testing requirements. The final performance testing provisions prohibit performance testing during SSM because these conditions are not representative of normal operating conditions. The final rule also requires, as proposed, that operators maintain records to document that operating conditions during the test represent normal operations. In light of NRDC v. EPA, 749 F.3d 1055 (D.C. Cir., 2014) (vacating affirmative defense provisions in the CAA section 112 rule establishing emission standards for Portland cement kilns), the EPA is also removing, as proposed, all of the regulatory affirmative defense provisions from the P&R I NESHAP at 40 CFR 480(j)(4) in its entirety and all other rule text that references these provisions ( i.e., the definition of affirmative defense in 40 CFR 63.482(b) and the reference to “§ 63.480(j)(4)” in 40 CFR 63.506(b)(1)(i)(A) and (b)(1)(i)(B)); and we did not receive any comments in opposition to these amendments.

The legal rationale and detailed revisions for SSM periods and the affirmative defense provision that we are finalizing here are set forth in the proposal preamble (see 88 FR 25080, April 25, 2023).

2. NSPS

The EPA has determined the reasoning in the court's decision in Sierra Club applies equally to CAA section 111 because the definition of “emission” or “standard” in CAA section 302(k), and the embedded requirement for continuous standards, also applies to the NSPS. Therefore, we are finalizing, as proposed, standards in NSPS subparts VVb, IIIa, NNNa, and RRRa that apply at all times, and more specifically during periods of SSM. The NSPS general provisions in 40 CFR 60.8(c) currently exempt non-opacity emission standards during periods of SSM. We are finalizing, as proposed, specific requirements in NSPS subparts IIIa, NNNa, and RRRa that override the general provisions for SSM (see 40 CFR 60.612a, 40 CFR 60.662a, and 40 CFR 60.702a, respectively).

E. What are the final amendments addressing the NSPS Subparts VV and VVa reconsideration?

In response to the January 2008 petition for reconsideration, we are finalizing, as proposed: (1) Definitions for “process unit” for NSPS subparts VV and VVa; (2) removal of the requirements in 40 CFR 60.482-1(g) (for NSPS subpart VV) and 40 CFR 60.482-1a(g) (for NSPS subpart VVa) that are related to a method for assigning shared storage vessels to specific process units; and (3) removal of the connector monitoring provisions from NSPS subpart VVa at 40 CFR 60.482-11a in their entirety. However, based on comments received on the proposed rulemaking, we are revising the value of “X” in the capital expenditure equation of NSPS subpart VVa to correct an erroneous phrasing that attached the value of “X” in the percent Y equation to the date of construction, reconstruction and modification (as opposed to date of physical or operational change). In the final rule, we have revised the “capital expenditure” definition in NSPS subpart VVa at 40 CFR 60.481a such that for owners or operators that made a physical or operational change to their existing facility prior to November 16, 2007, the percent Y is determined from the following equation: Y = 1.0 − 0.575 log X, where the value of “X” is 1982 minus the year of construction, and for owners or operators that made a physical or operational change to their existing facility on or after November 16, 2007, the percent Y is determined from the following equation: Y = 1.0 − 0.575 log X, where the value of “X” is 2006 minus the year of construction. Section IV.E.3 of this preamble provides a summary of key comments we received on the NSPS subparts VV and VVa reconsideration issues and our responses.

F. What other changes have been made to the NESHAP and NSPS?

This rule also finalizes, as proposed, revisions to several other NESHAP and NSPS requirements. We describe these revisions in this section as well as other proposed provisions that have changed since proposal.

To increase the ease and efficiency of data submittal and data accessibility, we are finalizing, as proposed, a requirement that owners or operators submit electronic copies of certain required performance test reports, flare management plans, and periodic reports (including fenceline monitoring reports for HON and the P&R I NESHAP) through the EPA's Central Data Exchange (CDX) using the Compliance and Emissions Data Reporting Interface (CEDRI) (see 40 CFR 63.108(e), 40 CFR 63.152(c) and (h), and 40 CFR 63.182(d) and (e) (for HON), 40 CFR 63.506(e)(6), and (i)(3) (for the P&R I NESHAP), and 40 CFR 63.528(a) and (d) (for the P&R II NESHAP), 40 CFR 60.486(l), and 60.487(a) and (g) through (i) (for NSPS subpart VV), 40 CFR 60.486a(l), and 60.487a(a) and (g) through (i) (for NSPS subpart VVa), 40 CFR 60.486b(l), and 60.487b(a) and (g) through (i) (for NSPS subpart VVb), 40 CFR 60.615(b), (j), (k), and (m) through (o) (for NSPS subpart III), 40 CFR 60.615a(b), (h) through (l), and (n), and 40 CFR 619a(e) (for NSPS subpart IIIa), 40 CFR 60.665(b), (l), (m), and (q) through (s) (for NSPS subpart NNN), 40 CFR 60.665a(b), (h), (k) through (n), and (p), and 40 CFR 669a(e) (for NSPS subpart NNNa), 40 CFR 60.705(b), (l), (m), and (u) through (w) (for NSPS subpart RRR), and 40 CFR 60.705a(b), (k) through (o), and (v), and 40 CFR 709a(e) (for NSPS subpart RRRa)). A description of the electronic data submission process is provided in the memorandum, Electronic Reporting Requirements for New Source Performance Standards (NSPS) and National Emission Standards for Hazardous Air Pollutants (NESHAP) Rules (see Docket Item No. EPA-HQ-OAR-2022-0730-0002). The final rule requires that performance test results collected using test methods that are supported by the EPA's Electronic Reporting Tool (ERT) as listed on the ERT website at the time of the test be submitted in the format generated through the use of the ERT or an electronic file consistent with the xml schema on the ERT website, and other performance test results be submitted in portable document format (PDF) using the attachment module of the ERT. For periodic reports (including fenceline monitoring reports), the final rule requires that owners or operators use the appropriate spreadsheet template to submit information to CEDRI. We have made minor clarifying edits to the spreadsheet templates based on comments received during the public comment period. The final version of the templates for these reports are located on the CEDRI website. The final rule requires that flare management plans be submitted as a PDF upload in CEDRI. Furthermore, we are finalizing, as proposed, provisions in the NSPS that allow facility operators the ability to seek extensions for submitting electronic reports for circumstances beyond the control of the facility, i.e., for a possible outage in the CDX or CEDRI or for a force majeure event in the time just prior to a report's due date, as well as the process to assert such a claim. For a more detailed discussion of these final amendments, see section III.E.3 of the proposal preamble (see 88 FR 25080, April 25, 2023), as well as sections IV.F and VI.B of this preamble.

Also, we are finalizing, as proposed, the restructuring of all HON definitions from NESHAP subparts G and H ( i.e., 40 CFR 63.111 and 40 CFR 63.161, respectively) into the definition section of NESHAP subpart F ( i.e., 40 CFR 63.101). To consolidate differences between certain definitions in these subparts, we are also finalizing the amendments we proposed in Table 30 of the proposal preamble (88 FR 25080, April 25, 2023), with only minor changes based on comments received on the proposed rulemaking. The comments and our specific responses to these items can be found in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

In addition, we are finalizing requirements, as proposed, at 40 CFR 63.114(a)(5)(v), 40 CFR 63.120(d)(1)(iii), 40 CFR 63.127(b)(4), and 40 CFR 63.139(d)(5) (for HON), and 40 CFR 63.484(t), 40 CFR 63.485(x), and 40 CFR 63.489(b)(10) (for the P&R I NESHAP) for owners or operators using adsorbers that cannot be regenerated and regenerative adsorbers that are regenerated offsite to use dual (two or more) adsorbent beds in series and conduct monitoring of HAP or TOC on the outlet of the first adsorber bed in series using a sample port and a portable analyzer or chromatographic analysis. However, we have clarified in the proposed rule text in this final action that the monitoring plan provisions in 40 CFR 63.120(d)(2) and (3) do not apply to HON sources subject to the monitoring provisions in 40 CFR 63.120(d)(1)(iii); and the monitoring plan provisions in 40 CFR 63.120(d)(2) and (3) do not apply to P&R I sources subject to the monitoring provisions in 40 CFR 63.120(d)(1)(iii) (via 40 CFR 63.484(t) and 40 CFR 63.485(x)). The comments and our specific responses to these items can be found in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

We are also finalizing, as proposed, several corrections to the calibration drift assessment requirements in NSPS subpart VVa at 40 CFR 60.485a(b)(2). These amendments include: (1) Correcting a regulatory citation to read “§ 60.486a(e)(8)” instead of “§ 60.486a(e)(7)”; (2) removing the extraneous sentence “Calculate the average algebraic difference between the three meter readings and the most recent readings and the most recent calibration value.”; (3) providing clarity in the mathematical step of the assessment by replacing the sentence “Divide this algebraic difference by the initial calibration value and multiply by 100 to express the calibration drift as a percentage.” with “Divide the arithmetic difference of the initial and post-test calibration response by the corresponding calibration gas value for each scale and multiply by 100 to express the calibration drift as a percentage.”; and (4) providing clarity by making other minor textural changes to the provisions related to the procedures for when a calibration drift assessment shows negative or positive drift of more than 10 percent. We did not receive any comments in opposition of these amendments.

In addition, we are finalizing, as proposed, the requirement in the HON and the P&R I and P&R II NESHAP, and NSPS subparts IIIa, NNNa, and RRRa to conduct subsequent performance testing on non-flare control devices no later than 60 calendar months after the previous performance test. The comments and our specific response to this item can be found in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

Also, we are finalizing, as proposed to: (1) Remove the provisions that allow compliance with certain portions of 40 CFR part 264, subpart AA or CC in lieu of portions of NESHAP subpart G (see 40 CFR 63.110(h)); and (2) remove the provisions that allow compliance with certain portions of 40 CFR part 65 in lieu of portions of NESHAP subparts G and H (see 40 CFR 63.110(i) and 40 CFR 60.160(g)). In addition, based on comments received on the proposed rulemaking, we are: (1) Revising 40 CFR 63.160(b)(1) and (c)(1) in the final rule such that compliance with HON subpart H constitutes compliance with NSPS subpart VVa provided the owner or operator continues to comply with 40 CFR 60.480a(e)(2)(i); and (2) revising 40 CFR 63.160(b)(1) and (c)(1) in the final rule such that compliance with HON subpart H constitutes compliance with NSPS subpart VVb provided the owner or operator continues to comply with 40 CFR 60.480b(e)(2)(i). We have also revised 40 CFR 60.480b(e)(2)(i) in the final rule to require compliance with 40 CFR 60.482-7b ( i.e., the standards for gas and light liquid valves in NSPS subpart VVb) in addition to the requirements of 40 CFR 60.485b(d), (e), and (f), and 40 CFR 60.486b(i) and (j). The comments and our specific responses to these items can be found in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

Finally, we are finalizing all of the revisions that we proposed for clarifying text or correcting typographical errors, grammatical errors, and cross-reference errors. These editorial corrections and clarifications are discussed in section III.E.5.f of the proposal preamble (see 88 FR 25080, April 25, 2023). We are also including several additional minor clarifying edits in the final rule based on comments received during the public comment period. The comments and our specific responses to these items can be found in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

G. What are the effective and compliance dates of the standards?

1. HON and the P&R I and P&R II NESHAP

For all of the requirements we are finalizing under CAA sections 112(d)(2), (3), and (6), and 112(h) (except for the removal of affirmative defense provisions in the P&R I NESHAP and fenceline monitoring requirements in HON and the P&R I NESHAP), all existing affected sources and all affected sources that were new sources under the previous HON and P&R I NESHAP ( i.e., sources that commenced construction or reconstruction after December 31, 1992 (for HON) or after June 12, 1995 (for the P&R I NESHAP), and on or before April 25, 2023), must comply with all of the amendments no later than July 15, 2027, or upon startup, whichever is later. For existing sources, CAA section 112(i) provides that the compliance date for standards promulgated under section 112(d) shall be as expeditious as practicable, but no later than 3 years after the effective date of the standard. Association of Battery Recyclers v. EPA, 716 F.3d 667, 672 (D.C. Cir. 2013) (“Section 112(i)(3)'s three-year maximum compliance period applies generally to any emission standard . . . promulgated under [section 112].”). We agree with the commenters (see section 11.1 of the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking) that 3 years is needed for owners and operators to implement the requirements we are finalizing under CAA sections 112(d)(2), (3), and (6). For example, for process vents, if an affected source has uncontrolled process vents that emit greater than or equal to 1.0 lb/hr of total organic HAP, then a new control system, such as a thermal oxidizer with piping, ductwork, etc., may need to be installed (due to the removal of the TRE concept in its entirety in the final rule). Also, additional permits ( e.g., New Source Review and/or a Title V permit modifications) may be required for new emission control equipment. Moreover, 3 years is needed to understand the final rule changes; revise site guidance and compliance programs; ensure operations can meet the standards during startup and shutdown; update operation, maintenance, and monitoring plans; upgrade emission capture and control systems; install new flare monitoring equipment; and install new process control systems. As provided in CAA section 112(i) and 5 U.S.C. 801(3), all new affected sources that commenced construction or reconstruction after April 25, 2023, are required to comply with all requirements under CAA sections 112(d)(2), (3), (6), and 112(h) (including fenceline monitoring) by July 15, 2024 or upon startup, whichever is later. We are also finalizing, as proposed, that owners or operators of P&R I affected sources must comply with the removal of the affirmative defense provisions 60 days after the publication date of the final rule (or upon startup, whichever is later). We provided additional rationale for these compliance dates in the preamble to the proposed rule (88 FR 25080, April 25, 2023).

In a change from the proposed rule, we have extended the compliance date for fenceline monitoring (with the exception of fenceline monitoring of chloroprene at P&R I affected sources producing neoprene, which is discussed later in this section) from 1 to 2 years. Owners and operators of all existing sources, and all affected sources that were new under the current rules— i.e., sources that commenced construction or reconstruction after December 31, 1992 (for HON) or after June 12, 1995 (for the P&R I NESHAP), and on or before April 25, 2023—must begin fenceline monitoring 2 years after the effective date of the final rule and, starting 3 years after the effective date of the final rule, must perform root cause analysis and apply corrective action requirements upon exceedance of an annual average concentration action level. We extended the timeline for fenceline monitoring from 1 to 2 years based on comments received, which indicated that EPA Method 327 will require laboratories to increase their capacity to meet the requirements for fenceline monitoring. We consider this expanded timeline to be necessary to allow commercial labs to conduct the needed method development, expand capacity, and develop the logistics needed to meet the requirements in the final rule. We also agree with commenters' other assertions that more time is needed to read and assess the new fenceline monitoring requirements; prepare sampling and analysis plans; develop and submit site-specific monitoring plans; identify representative, accessible, and secure monitoring locations for offsite monitors and obtain permission from the property owner to both place and routinely access the monitors; make any necessary physical improvements to fencelines to be able to site monitors, including construction of access roads, physical fencing, and potential drainage improvements; and obtain approval of any necessary capital expenditures. We consider 2 years to be necessary to allow for all of these things. For additional details, see section 11.1 of the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

For all of the requirements we are finalizing under CAA sections 112(f) for the HON, we are finalizing as proposed, except we are clarifying that the compliance dates we proposed are from the effective date of the rule rather than the publication date of the proposal. In other words, all existing affected sources and all affected sources that were new sources under the previous HON ( i.e., sources that commenced construction or reconstruction after December 31, 1992, and on or before April 25, 2023) must comply with the EtO requirements no later than July 15, 2026, or upon startup, whichever is later. As explained in the April 25, 2023, proposed rule (88 FR 25080, 25176), CAA section 112(f)(4) prescribes the compliance date for emission standards issued under CAA section 112(f). Ass'n of Battery Recyclers v. EPA, 716 F.3d 667, 672 (D.C. Cir. 2013) (“[S]ection 112(f)(4)'s two-year maximum applies more specifically to standards `under this subsection,' i.e., section 112(f).”). For existing sources, the earliest compliance date for CAA section 112(f) standards is 90 days. However, the compliance period can be extended up to 2 years if the EPA finds that more time is needed for the installation of controls. 42 U.S.C. 7412(f)(4)(B). The EPA finds that the new EtO provisions under CAA section 112(f) will require additional time to plan, purchase, and install emission control equipment. For example, for process vents, if an affected source cannot demonstrate 99.9-percent control of EtO emissions, or reduce EtO emissions to less than 1 ppmv (from each process vent) or 5 pounds per year (for all combined process vents), then a new control system, such as a scrubber with piping, ductwork, feed tanks, etc., may need to be installed. Similarly, this same scenario ( i.e., installation of a new control system, such as a scrubber with piping, ductwork, feed tanks, etc) may be necessary for storage vessels in order to reduce EtO emissions by greater than or equal to 99.9 percent by weight or to a concentration less than 1 ppmv. Likewise, a new steam stripper may be needed control wastewater with a total annual average concentration of EtO greater than or equal to 1 ppmw. Additionally, we agree with commenters (see section 11.1 of the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking) that additional permits may be required for these new emission control equipment ( e.g., New Source Review and/or a Title V permit modifications). In other words, sufficient time is needed to properly engineer the project, obtain capital authorization and funding, procure the equipment, obtain permits, and construct and start-up the equipment. Therefore, we are finalizing a compliance date of 2 years after the effective date of the final rule for all existing affected sources to meet the EtO requirements. All new affected sources that commence construction or reconstruction after April 25, 2023, are required to comply with the EtO requirements for the HON by July 15, 2024 or upon startup, whichever is later. This compliance schedule is consistent with the compliance deadlines outlined in the CAA under section 112(f)(4) and the CRA. We provided additional rationale for these compliance dates in the preamble to the proposed rule (88 FR 25080, April 25, 2023).

In a change from the proposed rule, the EPA is shortening the compliance deadline for affected sources producing neoprene, due to the EPA's finding that chloroprene emissions from the only such source pose an imminent and substantial endangerment under CAA section 303, 42 U.S.C. 7603. United States v. Denka Performance Elastomer, LLC, et al., No. 2:23-cv-00735 (E.D. La. filed Feb. 28, 2023). All existing affected sources producing neoprene and all affected sources producing neoprene that were new sources under the previous P&R I NESHAP ( i.e., sources that commenced construction or reconstruction after June 12, 1995, and on or before April 25, 2023) must comply with the chloroprene requirements we are finalizing under CAA section 112(f) for the P&R I NESHAP (see sections III.B.1 and IV.A.3.e of this preamble for a details about these chloroprene requirements) no later than October 15, 2024, or upon startup, whichever is later. However, such sources may seek the EPA's approval of a waiver from the 90-day compliance deadline and obtain a compliance date of up to July 15, 2026 if they demonstrate to the Administrator's satisfaction that “such period is necessary for the installation of controls” and that steps will be taken during the waiver period to assure that the public health of persons will be protected from any imminent endangerment. See 42 U.S.C. 112(f)(4)(B); 40 CFR 63.6(i)(4)(ii).

All new affected sources that commence construction or reconstruction after April 25, 2023, are required to comply with the chloroprene requirements for P&R I affected sources producing neoprene no later than by July 15, 2024 or upon startup, whichever is later. This compliance schedule is consistent with the compliance deadlines outlined in the CAA under section 112(f)(4) and the CRA, 5 U.S.C. 801.

2. NSPS Subparts VV, VVa, VVb, III, IIIa, NNN, NNNa, RRR, RRRa

All sources of equipment leaks in the SOCMI (regulated under NSPS subpart VVb) and all SOCMI air oxidation unit processes, distillation operations, and reactor processes (regulated under NSPS subparts IIIa, NNNa, and RRRa, respectively), that commenced construction, reconstruction, or modification on or after April 25, 2023, must meet the requirements of the new NSPS upon startup of the new, reconstructed or modified facility or by July 15, 2024, whichever is later. This compliance schedule is consistent with the requirements in section 111 of the CAA and the CRA.

Also, for NSPS subparts VV, VVa, III, NNN, and RRR, we are finalizing, as proposed, the change in format of the reporting requirements to require electronic reporting ( i.e., we are not finalizing any new data elements); and owners and operators must begin submitting performance test reports electronically beginning on July 15, 2024 and semiannual reports on and after July 15, 2025 or once the report template for the subpart has been available on the CEDRI website ( https://www.epa.gov/electronic-reporting-air-emissions/cedri ) for 1 year, whichever date is later. For NSPS subparts IIIa, NNNa, and RRRa, we are finalizing, as proposed, that owners and operators must submit performance test reports electronically within 60 days after the date of completing each performance test, and for NSPS subparts VVb, IIIa, NNNa, and RRRa, semiannual reports on and after July 15, 2024 or once the report template for the subpart has been available on the CEDRI website ( https://www.epa.gov/electronic-reporting-air-emissions/cedri ) for 1 year, whichever date is later.

IV. What is the rationale for our final decisions and amendments for the SOCMI, P&R I, and P&R II source categories?

For each issue, this section provides a description of what we proposed and what we are finalizing for the issue, the EPA's rationale for the final decisions and amendments, and a summary of key comments and responses. For all comments not discussed in this preamble, comment summaries and the EPA's responses can be found in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

A. Residual Risk Review for the SOCMI and Neoprene Production Source Categories NESHAP

1. What did we propose pursuant to CAA section 112(f) for the SOCMI and Neoprene Production source categories?

a. SOCMI Source Category

Pursuant to CAA section 112(f), the EPA conducted a residual risk review and presented the results of this review, along with our proposed decisions regarding risk acceptability and ample margin of safety, in the April 25, 2023, proposed rule for the SOCMI source category subject to HON (88 FR 25080). The results of the risk assessment for the proposal are presented briefly in Table 1 of this preamble. More detail is in the residual risk technical support document, Residual Risk Assessment for the SOCMI Source Category in Support of the 2023 Risk and Technology Review Proposed Rule (see Docket Item No. EPA-HQ-OAR-2022-0730-0085).

The results of the proposed chronic baseline inhalation cancer risk assessment at proposal indicated that, based on estimates of current actual and allowable emissions, the maximum individual lifetime cancer risk posed by the source category was 2,000-in-1 million driven by EtO emissions from PRDs (74 percent) and equipment leaks (20 percent). At proposal, the total estimated cancer incidence from this source category was estimated to be 2 excess cancer cases per year. Approximately 7.2 million people were estimated to have cancer risks above 1-in-1 million from HAP emitted from the facilities in this source category. At proposal, the estimated maximum chronic noncancer target organ-specific hazard index (TOSHI) for the source category was 2 for respiratory effects at two different facilities (from maleic anhydride emissions at one facility and chlorine emissions at another facility).

As shown in Table 1 of this preamble, the worst-case acute hazard quotient (HQ) (based on the reference exposure level (REL)) at proposal was 3 based on the RELs for chlorine and acrolein. In addition, at proposal, the multipathway risk screening assessment resulted in a maximum Tier 3 cancer screening value (SV) of 60 for mercury and 2 for cadmium for the fisher scenario, and 20 for polycyclic organic matter (POM) for the gardener scenario. At proposal, no site-specific assessment using TRIM.FaTE (which incorporates AERMOD deposition, enhanced soil/water run-off calculations, and model boundary identification) was deemed necessary. The EPA determined that it is not necessary to go beyond the Tier 3 lake analysis or conduct a site-specific assessment for cadmium, mercury, or POM. The EPA compared the Tier 3 screening results to site-specific risk estimates for five previously assessed source categories and concluded that if the Agency was to perform a site-specific assessment for the SOCMI source category, the HQ for ingestion exposure, specifically cadmium and mercury through fish ingestion, is at or below 1; and for POM, the maximum cancer risk under the rural gardener scenario would likely decrease to below 1-in-1 million. Also, at proposal, the highest annual average lead concentration of 0.004 micrograms per cubic meter (μg/m³ ) was well below the National Ambient Air Quality Standards (NAAQS) for lead, indicating low potential for multipathway risk of concern due to lead emissions.

At proposal, the maximum lifetime individual cancer risk posed by the 195 modeled facilities, based on whole-facility emissions, was 2,000-in-1 million, with EtO emissions from PRDs (74 percent) and equipment leaks (20 percent) from SOCMI source category emissions driving the risk. Regarding the noncancer risk assessment, the maximum chronic noncancer hazard index (HI) posed by whole-facility emissions was estimated to be 4 (for respiratory effects) due mostly (98 percent) to emissions from 2 facilities.

We weighed all health risk measures and factors, including those shown in Table 1 of this preamble, in our risk acceptability determination and proposed that the risks posed by the SOCMI source category under the current MACT provisions are unacceptable (section III.B of the proposal preamble, 88 FR 25080, April 25, 2023). At proposal, we identified EtO as the driver of the unacceptable risk and evaluated several options to control EtO emissions from (1) process vents, (2) storage vessels, (3) equipment leaks, (4) heat exchange systems, and (5) wastewater “in ethylene oxide service.” We also proposed requirements to reduce EtO emissions from maintenance vents, flares, and PRDs.

For process vents, we proposed to define “in ethylene oxide service” in the HON at 40 CFR 63.101 to mean each process vent in a process that, when uncontrolled, contains a concentration of greater than or equal to 1 ppmv undiluted EtO, and when combined, the sum of all these process vents would emit uncontrolled EtO emissions greater than or equal to 5 pounds per year (2.27 kilograms per year).

For storage vessels of any capacity and vapor pressure, we proposed to define “in ethylene oxide service” in the HON at 40 CFR 63.101 to mean that the concentration of EtO of the stored liquid is at least 0.1 percent by weight. Additionally, we proposed that unless specified by the Administrator, owners and operators may calculate the concentration of EtO of the fluid stored in a storage vessel if information specific to the fluid stored is available such as concentration data from safety data sheets. We also proposed that the exemption for “vessels storing organic liquids that contain organic hazardous air pollutants only as impurities” listed in the definition of “storage vessel” at 40 CFR 63.101 does not apply for storage vessels in EtO service.

For the EtO equipment leak provisions, we proposed to define “in ethylene oxide service” in the HON at 40 CFR 63.101 to mean any equipment that contains or contacts a fluid (liquid or gas) that is at least 0.1 percent by weight of EtO.

For heat exchange systems, we proposed to define “in ethylene oxide service” in the HON at 40 CFR 63.101 to mean each heat exchange system in a process that cools process fluids (liquid or gas) that are 0.1 percent or greater by weight of EtO.

For wastewater, we proposed to define “in ethylene oxide service” in the HON at 40 CFR 63.101 to mean each wastewater stream that contains total annual average concentration of EtO greater than or equal to 1 ppmw at any flow rate.

To reduce risks from process vents in EtO service, we proposed requirements at 40 CFR 63.113(j) to reduce emissions of EtO by either (1) venting emissions through a closed-vent system to a control device that reduces EtO by greater than or equal to 99.9 percent by weight, to a concentration less than 1 ppmv for each process vent, or to less than 5 lb/yr for all combined process vents; or (2) venting emissions through a closed-vent system to a flare meeting the flare operating requirements discussed in section III.B.4.a.i of the proposal preamble (88 FR 25080, April 25, 2023).

To reduce risks from storage vessels in EtO service, we proposed a requirement at 40 CFR 63.119(a)(5) to reduce emissions of EtO by either (1) venting emissions through a closed-vent system to a control device that reduces EtO by greater than or equal to 99.9 percent by weight or to a concentration less than 1 ppmv for each storage vessel vent; or (2) venting emissions through a closed-vent system to a flare meeting the flare operating requirements discussed in section IV.A.1 of the proposal preamble (84 FR 69182, December 17, 2019).

To reduce risks from equipment leaks in EtO service, we proposed the following combined requirements: monitoring of connectors in gas/vapor and light liquid service at a leak definition of 100 ppm on a monthly basis with no reduction in monitoring frequency or delay of repair (at 40 CFR 63.174(a)(3) and 40 CFR 63.174(b)(3)(vi)); light liquid pump monitoring at a leak definition of 500 ppm monthly (at 40 CFR 63.163(b)(2)(iv)); and gas/vapor and light liquid valve monitoring at a leak definition of 100 ppm monthly with no reduction in monitoring frequency or delay of repair (at 40 CFR 63.168(b)(2)(iv) and 40 CFR 63.168(d)(5)).

To reduce risks from EtO emissions due to heat exchange system leaks, we proposed at 40 CFR 63.104(g)(6) to require weekly monitoring for leaks for heat exchange systems in EtO service using the Modified El Paso Method, and if a leak is found, we proposed at 40 CFR 63.104(h)(6) that owners and operators must repair the leak to reduce the concentration or mass emissions rate to below the applicable leak action level as soon as practicable, but no later than 15 days after the sample was collected with no delay of repair allowed.

To reduce risks from wastewater in EtO service, we proposed at 40 CFR 63.132(c)(1)(iii) and (d)(1)(ii) that owners and operators of HON sources manage and treat any wastewater streams that are “in ethylene oxide service.” We also proposed at 40 CFR 63.104(k) to prohibit owners and operators from injecting water into or disposing of water through any heat exchange system in a CMPU meeting the conditions of 40 CFR 63.100(b)(1) through (3) if the water contains any amount of EtO, has been in contact with any process stream containing EtO, or the water is considered wastewater as defined in 40 CFR 63.101.

In addition, we proposed at 40 CFR 63.165(e)(3)(v)(D) that any release event from a PRD in EtO service is a violation of the standard to ensure that these process vent emissions are controlled and do not bypass controls. Also, in order to help reduce EtO risk from the SOCMI source category to an acceptable level, we proposed: (1) A requirement at 40 CFR 63.113(k)(4) that owners and operators cannot release more than 1.0 ton of EtO from all maintenance vents combined in any consecutive 12-month period; and (2) a requirement at 40 CFR 63.108(p) that owners and operators can send no more than 20 tons of EtO to all of their flares combined in any consecutive 12-month period from all HON emission sources at a facility.

After implementation of the proposed controls for: (1) Process vents, (2) storage vessels, (3) equipment leaks, (4) heat exchange systems, and (5) wastewater “in ethylene oxide service,” as well as implementation of the proposed requirements to reduce EtO emissions from maintenance vents, flares, and PRDs, we proposed that the resulting risks would be acceptable for the SOCMI source category. We determined at proposal that estimated post-control risks would be reduced to 100-in-1 million (down from 2,000-in-1 million) with no individuals exposed to risk levels greater than 100-in-1 million from HAP emissions from HON processes (see section III.B.2 of the proposal preamble, 88 FR 25080, April 25, 2023).

We then considered whether the existing MACT standards provide an ample margin of safety to protect public health and whether, taking into consideration costs, energy, safety, and other relevant factors, additional standards are required to prevent an adverse environmental effect. We noted that the EPA previously made a determination that the standards for the SOCMI source category provided an ample margin of safety to protect public health, and that the most significant change since that determination was the revised 2016 IRIS inhalation URE for EtO and new 2010 IRIS inhalation URE for chloroprene. As such, we focused our ample margin of safety analysis on cancer risk for EtO and chloroprene, since these pollutants, even after application of controls needed to get risks to an acceptable level, drive cancer risk and cancer incidence ( i.e., 60 percent of remaining cancer incidence is from EtO) for the SOCMI source category. The ample margin of safety analysis for the SOCMI source category identified no other control options for EtO beyond those proposed to reduce risks to an acceptable level. For chloroprene emissions from HON-subject sources, we identified control options for equipment leaks and maintenance activities; however, the options evaluated were found not to be cost-effective (see sections III.C.6 and III.D.4 of the proposal preamble, 88 FR 25080, April 25, 2023). Therefore, we proposed that the requirements that we proposed to achieve acceptable risk would also provide an ample margin of safety to protect public health (section III.B.3 of the proposal preamble, 88 FR 25080, April 25, 2023).

b. Neoprene Production Source Category

Pursuant to CAA section 112(f), the EPA conducted a residual risk review and presented the results of this review, along with our proposed decisions regarding risk acceptability and ample margin of safety, in the April 25, 2023, proposed rule for the Neoprene Production source category subject to the P&R I NESHAP (88 FR 25080). The results of the risk assessment for the proposal are presented briefly in Table 2 of this preamble. More detail is in the residual risk technical support document, Residual Risk Assessment for the Polymers & Resins I Neoprene Production Source Category in Support of the 2023 Risk and Technology Review Proposed Rule (see Docket Item No. EPA-HQ-OAR-2022-0730-0095).

The results of the proposed chronic baseline inhalation cancer risk assessment at proposal indicated that, based on estimates of current actual and allowable emissions, the MIR posed by the source category was 500-in-1 million, driven by chloroprene emissions from maintenance vents (67 percent), storage vessels (11 percent), wastewater (8 percent), and equipment leaks (4 percent). At proposal, the total estimated cancer incidence from this source category was estimated to be 0.05 excess cancer cases per year, or 1 cancer case every 20 years. Approximately 690,000 people were estimated to have cancer risks above 1-in-1 million from HAP emitted from this source category. At proposal, the estimated maximum chronic noncancer TOSHI for the source category was 0.05 for respiratory effects from chloroprene emissions.

As shown in Table 2 of this preamble, the worst-case acute HQ at proposal was 0.3 based on the REL for chloroform. In addition, at proposal, we did not undertake the three-tier human health risk screening assessment that was conducted for the SOCMI source category given that we did not identify reported persistent and bioaccumulative HAP (PB-HAP) emissions from the Neoprene Production source category. Instead, at proposal, we noted that we would expect dioxins likely to be formed by combustion controls used to control chlorinated chemicals such as chloroprene from this source category and concluded that risk from dioxins from the Neoprene Production source category would be lower than they are for the SOCMI source category after compliance with the proposed dioxin limit occurs. Also, because we did not identify reported PB-HAP emissions, we did not undertake the environmental risk screening assessment of PB-HAP for the Neoprene Production source category; however, we did conduct an environmental risk screening assessment for acid gases and concluded that no ecological benchmark was exceeded.

At proposal, the maximum lifetime individual cancer risk posed by the one neoprene production facility, based on whole-facility emissions, was 600-in-1 million, with chloroprene emissions from maintenance vents (66 percent total, 55 percent from neoprene production sources and 11 percent from HON sources), storage vessels (9 percent total, all from neoprene production sources), equipment leaks (7 percent total, 3 percent from neoprene production sources and 4 percent from HON sources), and wastewater (7 percent, all from neoprene production sources) driving the risk. Regarding the noncancer risk assessment, the maximum chronic noncancer TOSHI posed by whole-facility emissions was estimated to be 0.3 (for respiratory effects) due to chlorine emissions.

We weighed all health risk measures and factors, including those shown in Table 2 of this preamble, in our risk acceptability determination and proposed that the risks posed by the Neoprene Production source category under the current MACT provisions are unacceptable (section III.B of the proposal preamble, 88 FR 25080, April 25, 2023). At proposal, we identified chloroprene as the driver of the unacceptable risk and evaluated several options to control chloroprene emissions from (1) process vents, (2) storage vessels, and (3) wastewater “in chloroprene service.” We also proposed requirements to reduce chloroprene emissions from maintenance vents and PRDs, as well as a facility-wide chloroprene emissions cap for all neoprene production emission sources as a backstop.

For process vents, we proposed to define “in chloroprene service” in the P&R I NESHAP at 40 CFR 63.482 to mean each continuous front-end process vent and each batch front-end process vent in a process at affected sources producing neoprene that, when uncontrolled, contains a concentration of greater than or equal to 1 ppmv undiluted chloroprene, and when combined, the sum of all these process vents would emit uncontrolled, chloroprene emissions greater than or equal to 5 lb/yr (2.27 kg/yr).

For storage vessels of any capacity and vapor pressure in a process at affected sources producing neoprene, we proposed to define “in chloroprene service” in the P&R I NESHAP at 40 CFR 63.482 to mean that the concentration of chloroprene of the stored liquid is at least 0.1 percent by weight. Additionally, we proposed that unless specified by the Administrator, owners and operators may calculate the concentration of chloroprene of the fluid stored in a storage vessel if information specific to the fluid stored is available such as concentration data from safety data sheets. We also proposed that the exemption for “vessels and equipment storing and/or handling material that contains no organic HAP, or organic HAP as impurities only” listed in the definition of “storage vessel” at 40 CFR 63.482 does not apply for storage vessels in chloroprene service.

For wastewater, we proposed to define “in chloroprene service” in the P&R I NESHAP at 40 CFR 63.482 to mean each wastewater stream that contains total annual average concentration of chloroprene greater than or equal to 10.0 ppmw at any flow rate.

To reduce risks from process vents in chloroprene service, we proposed requirements at 40 CFR 63.485(y)(1) and 40 CFR 63.487(j)(1) to reduce emissions of chloroprene by either venting emissions through a closed-vent system to a non-flare control device that reduces chloroprene by greater than or equal to 99.9 percent by weight or to a concentration less than 1 ppmv for each process vent, or to less than 5 lb/yr for all combined process vents.

To reduce risks from storage vessels in chloroprene service, we proposed a requirement at 40 CFR 63.484(u)(1) to reduce emissions of chloroprene by either venting emissions through a closed-vent system to a non-flare control device that reduces chloroprene by greater than or equal to 99.9 percent by weight or to a concentration less than 1 ppmv for each storage vessel.

To reduce risks from wastewater in chloroprene service, we proposed at 40 CFR 63.501(a)(10)(iv) that owners and operators of P&R I sources producing neoprene manage and treat any wastewater streams that are “in chloroprene service.” We also proposed at 40 CFR 63.502(n)(8) to prohibit owners and operators from injecting water into or disposing of water through any heat exchange system in an EPPU if the water contains any amount of chloroprene, has been in contact with any process stream containing chloroprene, or the water is considered wastewater as defined in 40 CFR 63.482.

In addition, we proposed at 40 CFR 63.165(e)(3)(v)(D) that any release event from a PRD in chloroprene service is a violation of the standard to ensure that these process vent emissions are controlled and do not bypass controls. Also, in order to help reduce chloroprene risk from the Neoprene Production source category to an acceptable level, we proposed: (1) A requirement at 40 CFR 63.485(z) and 40 CFR 63.487(i)(4) that owners and operators cannot release more than 1.0 ton of chloroprene from all maintenance vents combined in any consecutive 12-month period; and (2) a facility-wide chloroprene emissions cap at 40 CFR 63.483(a)(10) that owners and operators cannot release more than 3.8 tpy in any consecutive 12-month period from all neoprene production emission sources, combined.

After implementation of the proposed controls for: (1) Process vents, (2) storage vessels, and (3) wastewater “in chloroprene service,” as well as implementation of the proposed requirements to reduce chloroprene emissions from maintenance vents, PRDs, and all neoprene production emission sources, combined, we proposed that the resulting risks would be acceptable from HAP emissions from the Neoprene Production source category. We determined at proposal that estimated post-control risks would be reduced to 100-in-1 million (down from 500-in-1 million) with no individuals exposed to risk levels greater than 100-in-1 million (see section III.B.2 of the proposal preamble, 88 FR 25080, April 25, 2023) from neoprene production emission sources.

We then considered whether the existing MACT standards provide an ample margin of safety to protect public health and whether, taking into consideration costs, energy, safety, and other relevant factors, additional standards are required to prevent an adverse environmental effect. We noted that the EPA previously made a determination that the standards for the Neoprene Production source category provided an ample margin of safety to protect public health, and that the most significant change since that determination was the new 2010 IRIS inhalation URE for chloroprene. As such, we focused our ample margin of safety analysis on cancer risk for chloroprene since this pollutant, even after application of controls needed to get risks to an acceptable level, drives cancer risk and cancer incidence ( i.e., 99.995 percent of remaining cancer incidence is from chloroprene) for the Neoprene Production source category. To determine whether the rule provides an ample margin of safety, we considered the chloroprene specific requirements that we proposed to achieve acceptable risks, as well as additional control requirements for chloroprene. The ample margin of safety analysis found that additional chloroprene controls would not be cost-effective, and therefore, we proposed that the requirements that we proposed to achieve acceptable risk would also provide an ample margin of safety to protect public health (section III.B.4 of the proposal preamble, 88 FR 25080, April 25, 2023). See the technical documents titled Residual Risk Assessment for the Polymers & Resins I Neoprene Production Source Category in Support of the 2023 Risk and Technology Review Proposed Rule; Analysis of Control Options for Process Vents and Storage Vessels to Reduce Residual Risk of Chloroprene Emissions at P&R I Affected Sources Producing Neoprene; and Analysis of Control Options for Wastewater Streams to Reduce Residual Risk of Chloroprene From Neoprene Production Processes Subject to P&R I (see Docket Item No. EPA-HQ-OAR-2022-0730-0095, -0083 and -0092, respectively).

2. How did the risk review change for the SOCMI and Neoprene Production source categories?

In response to comments received on the proposed rulemaking, we revised the risk assessments for the SOCMI and Neoprene Production source categories. The comments included our approach to modeling flares, which impacted the SOCMI baseline and post control risk assessments, and the performance standard for process vents and storage vessels in chloroprene service, which impacted the Neoprene Production post control risk assessment. The following sections provide the results of the revised risk assessments.

a. SOCMI Source Category

In response to a comment in section 1.1 of the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking, we modified our approach to modeling flares for the SOCMI source category and performed a revised risk assessment of baseline risk ( i.e., risk prior to the implementation of the control requirements described in this final action). Based on this revised risk assessment, the baseline MIR risk posed by the source category is 2,000-in-1 million driven by EtO emissions from PRDs (74 percent) and equipment leaks (20 percent). The total estimated cancer incidence due to emissions from this source category is estimated to be 2 excess cancer cases per year. Within 50 km (~31 miles) of HON-subject facilities, the population exposed to cancer risk greater than 100-in-1 million for HON actual and allowable emissions is approximately 83,000 people, and the population exposed to cancer risk greater than or equal to 1-in-1 million is approximately 7.17 million people. Of the 195 facilities that were assessed for risk, 8 facilities have an estimated maximum cancer risk greater than 100-in-1 million. In addition, the maximum modeled chronic noncancer TOSHI for the source category based on actual and allowable emissions is estimated to be 2 (for respiratory effects) at two different facilities (from maleic anhydride emissions at one facility and chlorine emissions at another facility). Approximately 83 people are estimated to be exposed to a TOSHI greater than 1. We note that the only change in these results from the proposal is the number of people exposed to cancer risk greater than 100-in-1 million for HON emissions, which decreased from 87,000 people at proposal to 83,000 people here. See Table 3 of this preamble for a summary of the HON baseline inhalation risk assessment results.

We conducted a revised assessment of facility-wide (or “whole-facility”) risk to characterize the source category risk in the context of whole-facility risk. The maximum lifetime individual cancer risk posed based on whole-facility emissions is 2,000-in-1 million with EtO emissions from PRDs (74 percent) and equipment leaks (20 percent) from SOCMI source category emissions driving the risk. The total estimated cancer incidence based on facility-wide emission levels is 2 excess cancer cases per year. Within 50 km (~31 miles) of HON-subject facilities, the population exposed to cancer risk greater than 100-in-1 million for HON facility-wide emissions is approximately 90,000 people, and the population exposed to cancer risk greater than or equal to 1-in-1 million is approximately 8.92 million people. The maximum chronic noncancer TOSHI posed by whole-facility emissions is estimated to be 4 (for respiratory effects) due mostly (98 percent) to emissions from 2 facilities. Emissions from one facility contribute to 83 percent of the TOSHI, with approximately 60 percent of the total TOSHI from non-source category emissions of chlorine and another 15 percent from source category emissions of chlorine. Emissions from the second facility contribute to 15 percent of the TOSHI, with approximately 11 percent of the total TOSHI from source category emissions of acrylic acid and 2 percent from source category emissions of acrylonitrile. Approximately 1,100 people are estimated to be exposed to a TOSHI greater than 1 due to whole-facility emissions. Again, we note that the only change in these results from the proposal is the number of people exposed to cancer risk greater than 100-in-1 million, which decreased from 95,000 people at proposal to 90,000 people here (due to our modified approach to modeling flares, discussed above).

Finally, we conducted a revised assessment to evaluate risks after implementation of the control requirements described in this action. After implementation of the controls, the MIR for the SOCMI source category is reduced to 100-in-1 million (down from 2,000-in-1 million) with no individuals exposed to risk levels greater than 100-in-1 million from HAP emissions from the SOCMI source category, which is the same as in the proposal. The total population exposed to risk levels from the SOCMI source category greater than or equal to 1-in-1 million living within 50 km (~31 miles) of a facility would be reduced from 7.17 million people to 6.27 million people. The cancer incidence would be reduced from 2 excess cancer cases per year to 0.4 excess cancer cases per year. The maximum modeled chronic noncancer TOSHI for the source category remains unchanged. Specifically, the chronic noncancer TOSHI is estimated to be 2 (for respiratory effects) at two different facilities (from maleic anhydride emissions at one facility and chlorine emissions at another facility) with approximately 83 people estimated to be exposed to a TOSHI greater than 1. The estimated worst-case off-site acute exposures to emissions from the SOCMI source category also remains unchanged, with a maximum modeled acute HQ of 3 based on the RELs for chlorine and acrolein. The only change in these results from proposal is the number of people exposed to cancer risk levels greater than or equal to 1-in-1 million (6.27 million here compared to 5.7 million at proposal) due to us not finalizing (in response to persuasive comments received during the public comment period) the requirement at 40 CFR 63.108(p) that would prohibit owners and operators from sending more than 20 tons of EtO to all of their flares combined in any consecutive 12-month period (for more information on this, see Section IV.A.3.d.v of this preamble). Table 4 of this preamble summarizes the reduction in risks due to emissions from the SOCMI source category based on the controls in this action. For further details on the revised risk assessment for the SOCMI source category, see the document titled Residual Risk Assessment for the SOCMI Source Category in Support of the 2024 Risk and Technology Review Final Rule, which is available in the docket for this rulemaking.

Table 4 of this preamble also summarizes the facility-wide risks for facilities in the SOCMI source category. The post-control facility-wide MIR remains 2,000-in-1 million, driven by EtO emissions from Polyether Polyols Production source category emissions sources, which the EPA intends to address in a future action. Further, we note that the fenceline monitoring action level of 0.2 μg/m³ for EtO will reduce EtO emissions and therefore risks below these levels, with the MIR reduced to 1,000-in-1 million or lower and the number of individuals exposed to cancer risk levels greater than 100-in-1 million and greater than or equal to 1-in-1 million expected to be lower than those in Table 4 of this preamble.

b. Neoprene Source Category

In response to a comment in section IV.A.3.e.i of this preamble, we revised the performance standard for process vents and storage vessels in chloroprene service for the Neoprene Production source category. This revision did not change the baseline source category or facility-wide risk assessments for the Neoprene Production source category from proposal (see section IV.A.1.b of this preamble and Table 5 of this preamble). The revised assessment indicated that, after implementation of the controls, the MIR for the Neoprene Production source category is 100-in-1 million (down from 500-in-1 million in the pre-control baseline) with no individuals exposed to risk levels greater than 100-in-1 million from HAP emissions from the Neoprene Production source category. This result is the same as in the proposal. The total population exposed to risk levels from the Neoprene Production source category greater than or equal to 1-in-1 million would be reduced from 690,000 people to 58,000 people. The total estimated cancer incidence of 0.05 drops to 0.01 excess cancer cases per year. For the risk results estimated after implementation of controls, the two changes from proposal are the number of people exposed to risk levels greater than or equal to 1-in-1 million (58,000 here compared to 48,000 at proposal) and the cancer incidence (0.01 here compared to 0.008 at proposal) from HAP emissions from the Neoprene Production source category. All other results remained the same. Table 5 of this preamble summarizes the reduction in cancer risks due to emissions from the Neoprene Production source category based on the controls in this action. For further details on the revised risk assessment for the Neoprene Production source category, see the document titled Residual Risk Assessment for the Polymers & Resins I Neoprene Production Source Category in Support of the 2024 Risk and Technology Review Final Rule, which is available in the docket for this rulemaking.

Table 5 of this preamble also provides the facility-wide risks for the facility in the Neoprene Production source category, which are of increased importance due to the secondary fenceline action level for chloroprene, before (pre-control baseline) and after controls (post-control) of neoprene production emission sources in this action. The post-control facility-wide MIR is 200-in-1 million, driven by chloroprene emissions from SOCMI and neoprene production emission sources. The secondary fenceline action level of 0.3 μg/m³ for chloroprene will further reduce chloroprene emissions and therefore risks below these levels, with the MIR expected to be 100-in-1 million or lower, with no individuals exposed to lifetime cancer risk levels greater than 100-in-1 million, and the number of people exposed to cancer risk levels greater than or equal to 1-in-1 million expected to be lower than those in Table 5 of this preamble.

3. What key comments did we receive on the risk review, and what are our responses?

This section provides summaries of and responses to the key comments received regarding our risk assessment for the SOCMI source category, our risk assessment for the Neoprene Production source category, the proposed requirements to reduce EtO emissions from the SOCMI source category, and the proposed requirements to reduce chloroprene emissions from the Neoprene Production source category. We received comments in support of and against the proposed residual risk review, the IRIS URE used in the review, and our determination that additional controls were warranted under CAA section 112(f)(2) for the SOCMI and Neoprene Production source categories. Other comments on these issues, as well as the EtO IRIS URE, chloroprene IRIS URE, and on additional issues regarding the residual risk review and the EPA's proposed changes based on the residual risk review, can be found in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

a. EtO IRIS URE

We received numerous comments in support of, and in opposition to, the EPA's use of the EtO IRIS value in assessing cancer risk for a source category under CAA section 112(f)(2) for EtO. After careful review of the comments, the Agency has determined that commenters did not identify new scientific information that would alter aspects of the EPA IRIS assessments or call into question the scientific judgments reflected in those assessments. The EPA continues to affirm its determination that the IRIS assessments are scientifically sound and robust and represent the best available inhalation cancer risk values for EtO. These comments are not summarized in this preamble. Instead, all of these comments (related to the EPA's use of the EtO IRIS value for CAA section 112(f)(2) risk assessment) and the EPA's responses are in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

b. Chloroprene IRIS URE

We received numerous comments in support of, and in opposition to, the EPA's use of the chloroprene IRIS value in assessing cancer risk for a source category under CAA section 112(f)(2) for chloroprene. After careful review of the comments, the Agency has determined that commenters did not identify new scientific information that would alter aspects of the EPA IRIS assessments or call into question the scientific judgments reflected in those assessments. The EPA continues to affirm its determination that the IRIS assessments are scientifically sound and robust and represent the best available inhalation cancer risk values for chloroprene. These comments are not summarized in this preamble. Instead, all of these comments (related to the EPA's use of the chloroprene IRIS value for CAA section 112(f)(2) risk assessment) and the EPA's responses are in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

c. Risk Assessment

Several commenters provided comments on specific facilities in the EPA risk assessment and submitted additional data for the EPA to use for assessing public health risks. We also received comments regarding environmental justice, our community-based risk assessment, and the statutory authority to assess risk. Key comments on these topics are as follows:

i. Emissions Data

Comment: Commenters objected to the use of the 2017 National Emissions Inventory (NEI) data without corrections or revisions to model risk. These commenters requested that the EPA incorporate all of the revisions that were provided by various companies that participated in the EPA's January 18, 2022, CAA section 114 request. A commenter explained that the EPA allowed facilities to update emissions values so the EPA's assessment was representative of current operations and improvements to both emissions controls and emissions estimation methodologies. The commenter pointed out that although several facilities provided revisions to the EPA for their NEI modeling file inputs, the EPA rejected many of them. The commenter contended that if the EPA corrected its emissions modeling file to reflect more accurate emissions levels or upgraded emissions controls, it would determine, for a number of facilities, that risks were acceptable, or some emissions units were not meaningfully contributing to risk.

Commenters provided the following specific examples of corrections facilities made to their 2017 NEI data, but were rejected by the EPA:

• Huntsman Petrochemical—Conroe Plant (ID 4945611); Conroe, TX

Used actual emissions for equipment leaks.

Used updated emission rates for holding ponds.

Used actual operation hours for pumps.

• Eastman Chemical Company—Texas Operations (ID 4941511); Longview, TX

Provided consistency with process vent stack test data.

Used refined El Paso Method response factors for cooling towers.

Used updated wastewater emissions calculations.

Used updated fugitive emissions calculations.

• Sasol Chemicals—Lake Charles Chemical Complex (ID 8468011); Westlake, LA

Removed a process vent not subject to HON.

Removed a transfer rack not subject to HON.

• BASF Corporation—Geismar Site (ID 8465611); Geismar, LA

Used more recent process vent stack test data.

• Clear Lake Plant (ID 4057911); Pasadena, TX

Used revised stream compositions to estimate equipment leak emissions.

Used revised calculation methodologies to estimate process vent emissions.

• Shell Chemical—Geismar Plant (ID 7445611); Geismar, LA

Installed a thermal oxidizer to reduce EtO emissions.

Used more accurate concentration data and targeted source control efforts for wastewater.

Used more frequent connector monitoring to estimate equipment leak emissions.

Changed the specification of residual EtO in Ethoxylate product to reduce EtO emissions.

Installed a thermal oxidizer on some process vents.

By incorporating the above revisions, commenters insisted the residual risk attributable to EtO would be reduced and the EPA would conclude that risks are acceptable, even if the current IRIS value for EtO is used.

A different commenter asserted that the EPA cannot rely on a single year of emissions data from HON and P&R I sources to evaluate residual risk. The commenter explained that the NEI does not provide a reliable basis for estimating downwind concentrations of specific HAPs and the resulting cancer or noncancer risk to the communities nearby. The commenter said that, by the EPA's conclusions, fenceline monitoring data has shown that modeled concentrations greatly underestimate monitored concentrations. The commenter contended that the reliance on 2017 NEI data would contradict the EPA's own statements and would not provide the ample margin of safety that the CAA requires. While the NEI can be used as a starting point, the commenter recommended that the EPA should select the highest annual emissions that each source has reported to either the Toxics Release Inventory (TRI) or the NEI within the most recent five-year period for which data are available. The commenter explained that TRI reports are filed annually and may provide a more accurate picture of current emissions, and it would be irrational to base a residual risk assessment for sources on the 2017 NEI when the same sources are reporting higher emissions in the 2017-2021 TRI or 2020 NEI reports.

Similarly, a commenter objected to the EPA's use of the 2019 baseline actual emissions for Denka Performance Elastomers, LLC to assess residual risk of chloroprene emissions. The commenter said that the 2019 baseline actual emissions are substantially lower than historic actual emission levels reported to the Louisiana Department of Environmental Quality (LDEQ) from 1991 through 2017; and the EPA's risk report does not appear to include a description of the primary causes for the observed 2019 emission reductions. The commenter added that the combined average 2019 community monitored chloroprene concentration is 2.5 times the EPA's 2019 modeled average fenceline concentration (0.74 μg/m³ ). The commenter also asserted that the 2019 actual annual baseline emissions do not reflect sustainable chloroprene emission reductions achieved through work practice standards or application of MACT emission controls given that the average chloroprene concentration measured at 5th Ward Elementary during the first 6 months of 2020 were ~52 percent higher than the measured 2019 concentrations.

Response: We disagree with commenters who object to the use of the 2017 NEI data. We relied on the January 2021 version of the 2017 NEI dataset because it provided the best available data for EtO emissions and other HAP emissions for the SOCMI source category and the Neoprene Production source category covered under the P&R I NESHAP. However, in a few instances where facility-specific data were not available or not reflective of current controls in the 2017 NEI, we attempted to obtain data from a more recent dataset ( e.g., review of emissions inventory data from our CAA section 114 request, more recent inventories submitted to states, or the 2018 NEI). Where we did not have better data, we did not update our dataset. Of note, for the one neoprene production facility (which is also part of the SOCMI source category), we used the 2019 emissions inventory that was provided to the EPA from our CAA section 114 request. The NEI data were also used to develop the other parameters needed to perform the risk modeling analysis, including the emissions release characteristics, such as stack heights, stack diameters, flow rates, temperatures, and emission release point locations.

We note that the EPA has an obligation to use the best available data for establishment of risk-based standards and generally updates the dataset where we have sufficient rationale or improved data ( e.g., relevant stack test data, documented process concentrations), but the EPA has discretion to reject updated emissions estimates when insufficient rationale and information is provided. In general, we rejected the corrections facilities made to their 2017 NEI data ( i.e., the corrections listed by commenters as specified in this comment summary) due to insufficient information when numbers were updated without a clear or substantive explanation of why emissions changed and where EPA could not fully verify the changes. For example, many suggested changes were due to revisions in the engineering calculation methods with no documented detailed calculations shown. Other examples include changing calculation input assumptions for the amount of HAP in process streams where no source testing/sampling was provided by commenters to support their suggested changes. Further, in many cases we also rejected corrections listed by commenters related to pollutants that drive cancer risks for HON ( i.e., EtO) and neoprene production sources ( i.e., chloroprene) given that we contend, based on the fenceline data, that the modeling file emissions for these pollutants are underestimated.

Regarding the commenter's objection to the EPA's use of the 2019 baseline actual emissions for Denka Performance Elastomers, LLC to assess residual risk of chloroprene emissions, the facility's emissions inventory was provided to the EPA pursuant to our CAA section 114 request. In particular, the EPA requested emission inventories from the past 5 years ( i.e., 2016-2020) from the facility's operations as part of this request. As 2017 NEI data did not represent current controls being employed at Denka Performance Elastomers, LLC, the EPA chose to use the most current data it had available, which is reflective of current operations and emissions. Given the EPA's concerns about decreased production and emissions in 2020 from the COVID-19 pandemic, we elected to use Denka Performance Elastomer, LLC's 2019 emissions inventory submitted as part of the CAA section 114 request in its risk assessment for the HON and Neoprene Production source categories in lieu of the 2017 NEI data. The EPA also reviewed chloroprene emission records to determine whether the emissions were associated with HON processes, neoprene processes, or other non-HON and non-neoprene processes and updated the regulatory code in the risk modeling input files to account for this review.

In summary, we took many steps to develop an emissions modeling file that was representative of emissions from HON and P&R I sources, including declining to revise data where we had insufficient rationale or information to verify commenters' suggested changes. As described in more detail in the preamble to the proposed rulemaking (88 FR 25080, April 25, 2023), the EPA used many sources of information to develop the HAP emissions inventory used to assess risks for this rulemaking, including, but not limited to, the 2017 NEI and information gathered under our CAA section 114 authority. The EPA typically has wide latitude in determining the extent of data-gathering necessary to solve a problem and courts generally defer to the agency's decision to proceed on the basis of imperfect scientific information, rather than to “invest the resources to conduct the perfect study.” Sierra Club v. EPA, 167 F. 3d 658, 662 (D.C. Cir. 1999) (“If the EPA were required to gather exhaustive data about a problem for which gathering such data is not yet feasible, the agency would be unable to act even if such inaction had potentially significant consequences . . . . [A]n agency must make a judgment in the face of a known risk of unknown degree.” Mexichem Specialty Resins, Inc., 787 F.3d. 561 (D.C. Cir. 2015)).

For further details on the assumptions and methodologies used to estimate actual emissions, see Appendix 1 of the documents titled Residual Risk Assessment for the SOCMI Source Category in Support of the 2024 Risk and Technology Review Final Rule and Residual Risk Assessment for the Polymers & Resins I Neoprene Production Source Category in Support of the 2024 Risk and Technology Review Final Rule, which are both available in the docket for this rulemaking.

Comment: A commenter contended that the EPA's inclusion of infrequent, episodic events in their risk assessment is inappropriate. The commenter explained that short-term or one-time emissions release events are not representative of concentrations an individual would be exposed to over a lifetime. Furthermore, the commenter contended that the EPA should also have excluded EtO emissions related to SSM events from its voluntary risk analysis because the EPA is statutorily obligated to address SSM events under CAA sections 112(d)(2) and (d)(3).

Response: If any operating period (including SSM periods) leads to noncompliance with standards, we would not model such noncompliance for purposes of assessing risk in the CAA section 112(f) risk review because the agency estimates risk based on compliance with the established NESHAP. The statute does not require the agency to determine risk based on some assumed level of noncompliance. In addition, the appropriate remedy for noncompliance with a NESHAP is an enforcement action seeking to require the source to come into compliance with the standard.

Emissions events in violation of the standards, whether or not they are caused by malfunction events, are not considered as part of risk analyses. The EPA interprets CAA section 112 as not requiring emissions that occur during periods of malfunction to be factored into development of CAA section 112 standards, and this reading has been upheld as reasonable by the U.S. Court of Appeals for the District of Columbia in U.S. Sugar Corporation v. EPA, 830 F.3d 579, 606-10 (D.C. Cir. 2016). Consistent with previous risk assessments, the EPA considered both allowable and actual emissions in assessing chronic inhalation exposure and risk under CAA section 112(f)(2) for the SOCMI source category and the Neoprene Production source category covered under the P&R I NESHAP (see, e.g., the National Emission Standards for Coke Oven Batteries [70 FR 19998-19999, April 15, 2005] and the proposed and final HON (71 FR 34428, June 14, 2006 and 71 FR 76603, December 21, 2006, respectively)). The final rule is designed to require sources to comply during all periods of operation. As explained in the preamble to the proposed rule (see 88 FR 25080, April 25, 2023), it is not generally possible to model malfunctions in the risk assessment, because by nature they are infrequent and unpredictable, and we generally have insufficient information to model these types of events. The main purpose of the risk review for these source categories is to evaluate whether the emission limits—the “standards promulgated pursuant to subsection (d),” not the non-compliance with those standards—should be made more stringent to reduce the risk posed after compliance with the underlying MACT standards. To the extent that a source is violating an underlying MACT standard, it is unlikely that tightening of the emission standard as a result of the residual risk review will avoid or mitigate such violations. In other words, a source that is violating a MACT emissions standard promulgated under CAA section 112(d) would not be any more likely to be able to avoid such violations and comply with a different presumably more stringent standard promulgated under CAA section 112(f). Such events are violations and subject to enforcement by the EPA, the states, or citizens, and an action for injunctive relief is the most effective means to address violations, whether or not they are caused by malfunctions, if an emissions event poses a significant health or environmental risk.

The EPA notes that the final Petroleum Refinery Sector Rule included a conservative, screening-level assessment (not a refined risk assessment) performed using available information collection response (ICR) data to see the impacts of certain non-routine emissions events from PRDs and flares. [80 FR 75178, December 1, 2015] That assessment conservatively combined routine and non-routine emissions merely to define an upper bound of combined risk, and the EPA ultimately concluded that risks were not significantly different, given the uncertainties and conservative nature of the screening. In this risk assessment, the EPA did have information on EtO emissions from PRD events at one facility as they were reported to the Texas Commission on Environmental Quality (TCEQ). The modeling indicated that emissions from one single PRD release contributed to the majority of the cancer risk for that facility and as such we proposed and are finalizing requirements that any releases from PRD in EtO service are violations of these emission standards. The EPA did not include other additional emission estimates from non-routine PRD or flare events in the emissions inventory that was used to assess residual risk. Other than for highly toxic compounds such as EtO and chloroprene, we have found that non-routine emissions from PRDs and flares in similar source categories, including ethylene production facilities and petroleum refineries, have not significantly affected risks (see, e.g.,85 FR 75187-75188, December 1, 2015).

ii. Environmental Justice

Comment: Commenters asserted that the EPA should continue to place environmental justice at the forefront as it moves through the regulatory process and ensure it takes steps to reduce impacts on overburdened communities. A commenter pointed out that populations with lung disease, children, people with heart disease, and others are typically at higher risk of health harm from air pollution. The commenter declared that the EPA must place a priority on ensuring the current administration meets its goals on improving environmental justice, ensuring that people who live near these facilities do not continue to face overlapping health inequities that increase their overall risk. Other commenters called attention to the 7 million people who live near chemical plants who face serious cancer risk from uncontrolled toxic air emissions and are majority Black and Brown residents. Commenters stated that chemical manufacturing facilities are commonly located in communities of color and low-income neighborhoods (especially in Texas and Louisiana) and the emissions reductions from the proposed standards will help reduce the burden on disproportionately impacted communities.

Another commenter asserted that the EPA should strengthen the proposed HON standards to further reduce HAP emissions with the goal of eliminating racial disparities in exposure at all risk levels. The commenter claimed that, even after adoption of the proposed rule, about 1.6 million people of color will still face serious cancer risk at the 1-in-1 million level simply by living within 10 km (6.2 miles) of toxic air emissions emitted by regulated sources from chemical manufacturing plants. The commenter contended that the EPA succeeded at identifying environmental justice concerns, however it failed to address these concerns. The commenter cited the EPA's environmental justice web page, specifically the phrase “no group of people should bear a disproportionate share of the negative environmental consequences,” and stated that people of color will still bear a disproportionate share of exposure to HAPs and resulting cancer risk if the HON rule is adopted as proposed. Furthermore, the commenter contended that the EPA failed to cite and analyze the scientific evidence that shows that people of color are also uniquely susceptible to the health effects of toxic air pollutants, in addition to being more highly exposed, due to the cumulative impacts from a combination with other psycho-social stressors including racism, poverty, lack of access to health care and healthful foods.

Response: The EPA is directed, to the greatest extent practicable and permitted by law, to make environmental justice part of its mission by identifying and addressing, as appropriate, disproportionate and adverse human health or environmental effects of its programs, policies, and activities on communities with environmental justice concerns. The EPA's environmental justice policies promote justice, including access to health impact data, by providing information on the types of environmental justice harms and risks that are prevalent in communities with environmental justice concerns. No such policies mandate consideration of any specific factors or particular outcomes from an action, but they direct that environmental justice analysis be performed as part of regulatory impact analysis, as appropriate, so that the public can have this information. As noted above, the assessment of costs and benefits described herein and in the RIA, including the environmental justice analysis, is presented for the purpose of providing the public with as full as possible an understanding of the potential impacts of this final action. The EPA notes that analysis of such impacts is distinct from the determinations finalized in this action under CAA sections 111 and 112, which are based solely on the statutory factors the EPA is required to consider under those sections.

The EPA evaluated the risks for various populations as described in the demographic analysis in the proposed rule preamble and in the documents titled Analysis of Demographic Factors for Populations Living Near Hazardous Organic NESHAP (HON) Operations—Final; Analysis of Demographic Factors for Populations Living Near Hazardous Organic NESHAP (HON) Operations: Whole Facility Analysis—Final; Analysis of Demographic Factors for Populations Living Near Neoprene Production Operations—Final; Analysis of Demographic Factors for Populations Living Near Neoprene Production Operations: Whole Facility Analysis—Final; and Analysis of Demographic Factors for Populations Living Near Polymers and Resins I and Polymer and Resins II Facilities, which are available in the docket for this rulemaking. The EPA used its Environmental Justice Risk and Proximity Analysis Tool (“EJ Tool”) to link HEM/AERMOD modeling results for the HON and P&R sources with detailed census data, in order to evaluate the distribution of cancer and noncancer risks for different demographic factors (including racial, ethnic, age, economic, educational, and linguistically isolated population categories). In addition to evaluating risk distribution, this analysis also presents the demographic composition of the population located within close proximity (10 km) and within the overall HEM/AERMOD model domain (50 km) of the source category emissions (irrespective of risk). The following demographic groups were included in this risk and proximity analysis:

Total population;

White;

Black (or African American);

American Indian or Alaska Native;

Other races and multiracial;

Hispanic or Latino;

Children 17 years of age and under;

Adults 18 to 64 years of age;

Adults 65 years of age and over;

Adults without a high school diploma;

People living below the poverty level, and

Linguistically isolated people.

The total population statistics near facilities in the source category, irrespective of risk ( i.e., at all risk levels) are in the Analysis of Demographic memorandum. These results indicate that the demographic composition of the population located within close proximity (10 km) and within the overall HEM/AERMOD model domain (50 km) of the source category emissions are the same or lower than the nationwide average for all communities of environmental justice concern.

Considering risk, the post-control scenario is expected to reduce cancer incidence across all demographic groups including communities of environmental justice concern. Regarding the commenter's concern about the post-control risk exposure of people of color, the requirements for the HON/SOCMI facilities reduce the chronic cancer risks for Black individuals as follows: >100-in-1 million from 12,000 people to zero people; ≥50-in-1 million from 59,000 to 4,000; and ≥1-in-1 million from 694,000 to 692,000. The rule has the greatest impact at the higher chronic cancer risk levels. Additionally, regarding concern about the unique susceptibility of people of color to the health impacts of toxic air pollutants, the EPA is currently exploring data and methods to make it possible to more explicitly evaluate the role of non-chemical stressors in an environmental justice analysis.

iii. Community-Based Risk Assessment

Comment: Commenters said that they supported the addition of the EPA's community-based risk assessment in the rulemaking proposal given that it reflects a commitment to evidence-based decision-making and the well-being of communities affected by these facilities, and implored the EPA to continue to employ rigorous community risk assessments in future rulemakings. A commenter remarked that in addition to the communities' benefit, workers within chemical plants would benefit as well.

Some commenters supported the EPA expanding the community-based risk assessment to include air toxics-related cancer risks from all large facilities in communities in the vicinity, including sources that would not be covered by the rule. The commenters explained that since the public's exposure is not limited to one chemical or source category at a time, this is a step in the right direction. The commenters suggested these expanded community-based risk assessments be standard practice. Other commenters proposed to expand the community-based risk assessment to not only include all large facilities in the area, but also include other types of sources ( e.g., mobile sources), include non-cancer endpoints ( e.g., miscarriages, birth defects, neurodevelopmental impacts), and explore other routes of exposure beyond inhalation. Commenters claimed this could be accomplished if the EPA went a step further than the community risk assessment and performed a cumulative risk assessment. The commenter explained that a cumulative risk assessment would take into account chemical and non-chemical stressors, and how these stressors interact to promote adverse health effects.

Other commenters asserted that the EPA should strengthen the proposed HON standards to further reduce HAP emissions with the goal of eliminating or reducing the number of people exposed at or above 1-in-1 million cancer risk to the maximum extent feasible. A commenter claimed that, under the proposed rule, about 5.7 million people would still face serious cancer risk at the 1-in-1 million level simply by living within 50 km (31 miles) of toxic air emissions that are being emitted by regulated sources from chemical manufacturing plants. The commenter further claimed that, by living within 10 km (6.2 miles), there is only a 10 percent reduction of total people at this risk level. The commenter contended that the EPA has done more in the past, specifically when 99 percent of the population living within 50 km had cancer risk reduced to 1-in-1 million through the Benzene NESHAP rule.

On the contrary, a commenter argued that the EPA's “whole-facility” and “community-based” risk assessments are irrelevant to the proposed rule because the EPA is limited to considering only risks associated with the source category that is the subject of the risk assessment. The commenter added these broader risk analyses are less reliable due to uncertainties in the data used.

Response: We appreciate the commenters' support of the community-based risk assessment. In response to reducing the number of people exposed at or above 1-in-1 million cancer risk to the maximum extent feasible, the EPA's ample margin-of-safety determinations are conducted in accord with the two-step framework set forth in the Benzene NESHAP. When making its ample margin of safety determination, the EPA does consider health risks and their associated uncertainties, but also considers costs, technical feasibility, and other factors. For the SOCMI source category, in Step 1 of the Benzene NESHAP framework, the risks were determined to be unacceptable given all of the health information. Standards were proposed to bring the risk down to acceptable levels, not considering costs. Once the risks were determined to be at acceptable levels, Step 2 of the Benzene NESHAP framework requires the EPA to again consider health risks, but also cost, technical feasibility, and other factors, in determining if any additional controls should be required to achieve an ample margin of safety. For the SOCMI source category, the EPA proposed that it was not appropriate to require additional controls (either based on costs, feasibility, or availability) beyond what were proposed to achieve acceptable risks, regardless of health risks, thus we concluded that the proposed standards to address unacceptable risks also achieved an ample margin of safety.

Comment: Some commenters asserted that the community-based risk assessments should be used when making regulatory decisions, although there may be implementation challenges due to potential limitations in the EPA's statutory authority. A commenter explained that the CAA requires the EPA to investigate whether its regulations provide an “ample margin of safety” to protect public health, and if a community risk assessment demonstrates that a proposed rule does not provide an “ample margin of safety” (because of other health stressors in the community not captured by other risk assessments), then the EPA should revise the proposed rule.

Response: Section 112(f)(2) of the CAA expressly preserves our use of the two-step process for developing standards to address residual risk and interpret “acceptable risk” and “ample margin of safety” as developed in the Benzene NESHAP (54 FR 38044, September 14, 1989). In the Benzene NESHAP, the EPA concluded that “With respect to considering other sources of risk from benzene exposure and determining the acceptable risk level for all exposures to benzene, EPA considered this inappropriate because only the risk associated with the emissions under consideration are relevant to the regulation being established and, consequently, the decisions being made.” (54 FR 38044, September 14, 1989). Our authority to use the two-step process set forth in the Benzene NESHAP, and to consider a variety of measures of risk to public health, is discussed more thoroughly in the preamble to the proposed rule (see 88 FR 25080, April 25, 2023). Nothing in the CAA or the Benzene NESHAP in any way forecloses us from considering facility-wide risks in making a determination under CAA section 112(f)(2), as such information can constitute relevant health information.

Although not appropriate for consideration in the determination of acceptable risk presented by just source category emissions, we note that contributions to risk from sources outside the source category under review could be one of the relevant factors considered in the ample margin of safety determination, along with cost and economic factors, technological feasibility and other factors. For the SOCMI source category, the EPA proposed that it was not appropriate to require additional controls (either based on costs, feasibility, or availability) beyond what were proposed to achieve acceptable risks, regardless of health risks, thus we concluded that the proposed standards to address unacceptable risk posed by emissions from the SOCMI source category also achieved an ample margin of safety.

The development of community-based estimates provides additional information about the potential cumulative risks in the vicinity of the RTR sources, as one means of informing potential risk-based decisions about the RTR source category in question. We recognize that, because these risk estimates were derived from facility-wide emissions estimates which have not generally been subjected to the same level of engineering review as the source category emission estimates, they may be less certain than our risk estimates for the source category in question, but they remain important for providing context as long as their uncertainty is taken into consideration in the process.

iv. Statutory Authority To Conduct Risk Assessment

Comment: Commenters argued that the EPA is obligated to consider costs as part of their optional second residual risk review. Some commenters said that the EPA's refusal to consider costs of the controls proposed to reduce EtO emissions is beyond the EPA's statutory authority, and is arbitrary and capricious. The commenters said that unless specifically instructed otherwise, rational decision making requires the consideration of cost. The commenters contended that unless a statute precludes consideration of costs, “[c]onsideration of cost reflects the understanding that reasonable regulation ordinarily requires paying attention to the advantages and the disadvantages of agency decisions.” Michigan v. EPA, 576 U.S. 743, 754 (2015). Some commenters added that the Supreme Court has before held that consideration of costs must occur when the EPA finds that it is “appropriate and necessary” to regulate emissions under the CAA. Michigan v. EPA., 576 U.S. 743, (2015) (holding costs must be considered when determining whether it is “appropriate and necessary” to regulate stationary sources of fossil-fuel fired power plants under CAA section 7412(n)). A commenter opined that because it would be “unreasonable to read an instruction to an administrative agency to determine whether `regulation is appropriate and necessary' as an invitation to ignore costs,” similarly, it would be unreasonable here for the EPA to ignore costs after it discretionally determined that it was “necessary” to “revisit and revise” the residual risk threshold.

The commenters said the residual risk provisions, by reference to the Benzene NESHAP, allow the EPA to exclude costs only in initially determining acceptable risk, but in setting an ample margin of safety, costs are to be considered. The commenters contended that if the EPA has authority to conduct subsequent residual risk findings (which the commenters dispute), then the entire exercise is a secondary one that must take cost into consideration. A commenter explained that under most circumstances under CAA section 112, even when as an initial step, consideration of cost may be prohibited, the CAA requires consideration of cost in subsequent steps and Congress has constrained circumstances under which cost cannot be considered; therefore, the EPA is acting contrary to Congressional intent by attempting to expand its authority to conduct a risk review more than once, which is the only way in which the EPA could attempt to revise the NESHAP without considering costs.

Commenters cited the following court rulings and other references to support their view that the EPA is obligated to consider costs as part of their optional second residual risk review:

• White Stallion Energy Center, LLC v. E.P.A., 748 F.3d 1222 (2014) (Kavanaugh concurring in part and dissenting in part) (citing and quoting RICHARD L. REVESZ & MICHAEL A. LIVERMORE, RETAKING RATIONALITY 12 (2008) (“For certain kinds of governmental programs, the use of cost-benefit analysis is a requirement of basic rationality.”).
• Richard J. Pierce, Jr., The Appropriate Role of Costs in Environmental Regulation, 54 ADMIN. L.REV. 1237, 1247 (2002) (“All individuals and institutions naturally and instinctively consider costs in making any important decision . . . . [I]t is often impossible for a regulatory agency to make a rational decision without considering costs in some way.”)
• the Supreme Court pointed out inEntergy Corp. v. Riverkeeper, Inc., 556 U.S. 208, 224 (2009), that the EPA had long determined that it was unreasonable to interpret a statute in a way “as requiring use of technology whose cost is wholly disproportionate to the environmental benefit to be gained.” (quoting In re Public Service Co. of New Hampshire, 1 E.A.D. 332, 340 (1977)). While Entergy Corp. was in the context of the Clean Water Act, the same logic applies equally here. Justice Breyer reiterated in Entergy Corp., agencies should not read statutes in a way that forbids cost-benefit comparisons when the language does not require doing so. As Justice Breyer explained, not only would that be “difficult to enforce” because “every real choice requires a decisionmaker to weigh advantages against disadvantages, and disadvantages can be seen in terms of (often quantifiable) costs,” but such “absolute prohibition would bring about irrational results.”
• the Supreme Court has concluded that “[n]o regulation is `appropriate' if it does significantly more harm than good,” and reminds agencies that “[c]onsideration of cost reflects the understanding that reasonable regulation ordinarily requires paying attention to the advantages and the disadvantages of agency decisions [reflecting] the reality that too much wasteful expenditure devoted to one problem may well mean considerably fewer resources available to deal effectively with other (perhaps more serious) problems.”Michigan v. EPA at 752-53 (internal quotations omitted); see also id. (Kagan, J. dissenting) (“Cost is almost always a relevant—and usually, a highly important—factor in regulation”)

Response: The EPA disagrees that it was unconditionally obligated to consider costs in this CAA section 112(f)(2) risk review. As explained in response to a comment in section 1.5 of the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking, the EPA has the authority to conduct an additional risk review, particularly where new information has come to light making a prior risk review unreliable. New information became available about both chloroprene and EtO in 2010 and 2016, respectively. After the EPA completed development of the IRIS inhalation URE for chloroprene in 2010 and updated the IRIS inhalation URE for EtO in 2016, the EPA learned that chloroprene and EtO were more toxic than previously known. These updates came after the first risk reviews were conducted for the SOCMI and Neoprene Production (within the P&R I NESHAP) source categories and therefore prompted the EPA to reevaluate residual cancer risks caused by EtO and chloroprene emissions.

This reevaluation meant that reconsideration of our original decisions under CAA section 112(f)(2) for the SOCMI and Neoprene Production source categories is warranted, beginning with whether the existing standards reduce risks to acceptable levels under the Benzene NESHAP. Under the Benzene NESHAP, this meant going through both the (1) acceptability and (2) ample margin of safety steps of the section 112(f)(2) analysis. Only by going through both analytical steps anew could the EPA account for the corrected scientific understanding of risks from these HAP and conduct the appropriately updated residual risk reviews.

Under the approach outlined in the Benzene NESHAP, National Emissions Standards for Hazardous Air Pollutants: Benzene Emissions from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery Plants (54 FR 38,044, September 14, 1989), the EPA evaluates residual risk and develops standards under CAA section 112(f)(2) in two steps, as some commenters correctly stated. See Proposed Rule, 88 FR at 25,089. In step (1), the EPA determines whether risks are acceptable “consider[ing] all health information, including risk estimation uncertainty, and includes a presumptive limit on maximum individual lifetime [cancer] risk (MIR) of approximately 1 in 10 thousand.” 54 FR at 38,045. If risks are unacceptable, the EPA must determine the emissions standards required to reduce risk to an acceptable level without considering costs. In step (2), the EPA considers whether the emissions standards provide an “ample margin of safety” to protect public health “in consideration of all health information, including the number of persons at risk levels higher than approximately 1 in 1 million, as well as other relevant factors, including costs and economic impacts, technological feasibility, and other factors relevant to each particular decision.” Id. (emphasis added). The EPA must then promulgate or revise emission standards necessary to provide an ample margin of safety to protect public health or determine that the standards being reviewed provide an ample margin of safety without any revisions. After conducting the ample margin of safety analysis, we consider whether a more stringent standard is necessary to prevent, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect.

It is true that CAA section 112(f)(2) does not contain words declaring that consideration of costs in assessing risk acceptability is prohibited. However, this Benzene NESHAP approach was incorporated by Congress into CAA section 112(f)(2) in the 1990 CAA amendments and was upheld by the United States Court of Appeals for the District of Columbia Circuit. See NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008); Proposed Rule, 88 FR at 25,089. The approach is both rational and reasonable. While the statute does not expressly forbid consideration of costs at step (1), the Benzene NESHAP which the EPA promulgated in response to the D.C. Circuit's ruling in NRDC v. EPA, 824 F.2d 1146 (D.C. Cir. 1987) ( Vinyl Chloride ), and Congress's endorsement of that approach in enacting the 1990 Amendments to section 112, have long been understood to prohibit consideration of costs at step (1).

The new information gained by the 2010 chloroprene and 2016 EtO IRIS inhalation UREs warranted a complete re-analysis of both steps for the HON and Neoprene Production rules. The EPA therefore started back at step (1), acceptability, in which costs are not considered. Starting back at step (1) was essential to ensure that the risks due to EtO and chloroprene were being adequately addressed given the EPA's new understanding that exposure to EtO and chloroprene poses greater risk than was previously known. The EPA could not simply adjust the risk review at the step (2) ample margin of safety analysis to correct any errors and account for the new understanding. As explained elsewhere in this preamble, the EPA has analyzed acceptability of risks from HON and Neoprene Production processes under step (1) and identified controls necessary to achieve acceptability. Moreover, the EtO and chloroprene emission standards for HON and Neoprene Production processes that the EPA is promulgating are all necessary to reduce risks from HAP emissions from the SOCMI and Neoprene Production source categories to acceptable levels, and the EPA is not adopting further source category- specific emission standards under CAA section 112(f)(2) under step (2) of the Benzene NESHAP. Consequently, the EPA does not agree that the cases commenters cited require that the EPA must or even can consider costs in determining these risk acceptability-based standards for process emissions from these source categories.

Comment: A commenter argued that the EPA should not be carrying out a cost-blind residual risk review for chloroprene when other options to address air toxics risks are available that do take costs into consideration. The commenter pointed out that on May 6, 2021, the EPA's Office of Inspector General (OIG) issued Report No. 21-P-0129: EPA Should Conduct New Residual and Technology Reviews for Chloroprene- and Ethylene July 7, 2023, 61 Oxide-Emitting Source Categories to protect Human Health (“OIG Report”). The commenter said that the EPA's Office of Air and Radiation (OAR) submitted three responses to the OIG Report in which they reiterated: (1) That they are not statutorily required to conduct another residual risk review of chloroprene and (2) that they have multiple options to address risks associated with chloroprene that do not require a cost-blind residual risk review. The commenter stated that OAR explained to OIG that it can consider risks during a technology review and that the EPA has “multiple tools available under the CAA for addressing risk from emissions of air toxics” besides discretionary residual risk reviews under CAA section 112(f).

Other commenters cited various court rulings to support their view that the EPA should withdraw the risk review requirements and repropose with cost consideration under the technology review provisions of the CAA:

• As Justice Kagan noted: “Unless Congress provides otherwise, an agency acts unreasonably in establishing `a standard-setting process that ignore[s] economic considerations.' ” Id. (Kagan, J. dissenting) (quotingIndustrial Union Dep't v. American Petroleum Institute, 448 U.S. 607, 670 (1980) (Powell, J., concurring in part and concurring in judgment)).” Commenters argue that the approach that Justice Kagan warned against is exactly what the EPA has done here.
• the EPA has acted unreasonably, particularly as “Federal administrative agencies are required to engage in “reasoned decision-making.”Allentown Mack Sales & Service, Inc. v. NLRB, 522 U.S. 359, 374(1998) (internal quotation marks omitted). “Not only must an agency's decreed result be within the scope of its lawful authority, but the process by which it reaches that result must be logical and rational.”
• It follows that agency action is lawful only if it rests “on a consideration of the relevant factors.”State Farm 463 U.S. at 43, (internal quotation marks omitted).” Michigan, 576 U.S. at 750. Commenters argue one of those factors is cost.

Response: As explained above, cost is considered in one of the two steps that the EPA undertakes during a residual risk review under 112(f)(2). The residual risk review is not “cost-blind.”

The commenter quotes specific portions of OAR's response to OIG, which may not give the full picture of OAR's position in its response. For completion, the response stated:

[I]n those situations where we are reviewing a NESHAP and there is new information on the toxicity of a given chemical of interest (and the statutorily-required residual risk review has already been completed for that source category), we will determine how to best consider the new risk information in the current review. As described in the roadmaps discussed in our response to Recommendation 2, we will evaluate the multiple tools available under the CAA for addressing risk from emissions of air toxics. Those tools include conducting a discretionary residual risk assessment under CAA section 112(f)(2), conducting a review under CAA section 112(d)(6), and/or establishing new standards for unregulated pollutants if the original NESHAP did not regulate all HAP. We intend to use these tools to reduce risk—consistent with the law and in a sequence that provides an ample margin of safety to protect public health.

(Emphasis in original.)

As OAR stated in the above response, there are multiple tools available to “address” risk from emissions of air toxics, and OAR said it would evaluate those tools, which may include a CAA section 112(d)(6) review. But the EPA did not say that it commonly “considers” risk in a CAA section 112(d)(6) review, or that risk is a factor that must drive a regulatory decision under CAA section 112(d)(6). The EPA considers the public health and environmental risks from HAP emissions during the CAA section 112(f) phase of regulation, when the EPA considers any residual risk after technology-based CAA section 112(d)(2) standards are implemented. However, when the EPA revises standards under CAA section 112(d)(6) and imposes additional controls or work practice standards that lead to HAP emission reductions, risk from those HAP emission reductions is inherently addressed to some degree given that reduced emissions will correlate to some degree of reduced risk. While the EPA does not have to directly consider risk in the CAA section 112(d)(6) analysis, risks are lowered when additional emission controls are imposed as a result of those standards.

However, in the case of the SOCMI and Neoprene Production standards, the risks were so significantly affected by the IRIS values for EtO and chloroprene that it became clear that a full risk review under CAA section 112(f)(2) was warranted, rather than relying on ancillary risk benefits that might result from conducting only a CAA section 112(d)(6) technology review. Consequently, under the Benzene NESHAP approach incorporated by CAA section 112(f), as explained above, we had to re-assess whether the existing standards were sufficiently protective, and we determined that they did not reduce risks to acceptable levels. The standards adopted in the final rulemaking are based on what is necessary to reduce risks to acceptable levels under the Benzene NESHAP, and therefore may not be based on consideration of costs. However, our rulemaking analyses do estimate the costs that will result from compliance with the standards, even if that information did not drive regulatory decisions. For details on the assumptions and methodologies used in the costs and impacts analyses, see the technical documents titled Analysis of Control Options for Process Vents and Storage Vessels to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Equipment Leaks to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Heat Exchange Systems to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Wastewater Streams to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Flares to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Process Vents and Storage Vessels to Reduce Residual Risk of Chloroprene Emissions at P&R I Affected Sources Producing Neoprene; and Analysis of Control Options for Wastewater Streams to Reduce Residual Risk of Chloroprene From Neoprene Production Processes Subject to P&R I (see Docket Item No. EPA-HQ-OAR-2022-0730-0074, -0003, -0071, -0087, -0070, -0083 and -0092, respectively).

Comment: A commenter argued that the Agency arbitrarily fails to properly implement the authority it claims to possess. The commenter pointed out that the EPA does not limit its review to chloroprene and EtO ( e.g., in presenting the results of its risk assessment, the EPA concludes that maleic anhydride, chlorine, acrylic acid, and acrylonitrile present the highest acute inhalation risks for the SOCMI source category) even though the EPA claims a second residual risk review is only warranted for chloroprene and EtO because of the IRIS reassessments. The commenter claimed that the EPA's approach is arbitrary and unfounded because the Agency asserts no basis for conducting a new risk review for any pollutants other than chloroprene and EtO.

Response: As explained above in response to another comment in this section of this preamble, new information about risks of chloroprene and EtO exposure has come to light, warranting an updated residual risk review for the SOCMI and Neoprene Production (within the P&R I NESHAP) source categories. This risk review was conducted in accordance with longstanding, congressionally and judicially approved steps laid out in the 1989 Benzene NESHAP. Those steps account for the risk due to emissions of all HAP from a source category and the risk review is not limited to one or two HAP solely because updated risk information is available for only two HAP. Therefore, in order to make risk acceptability and ample margin of safety determinations for each source category, we assessed risks for all HAP emitted by the SOCMI and Neoprene Production source categories.

Importantly, though, the EPA is only imposing new standards under CAA section 112(f)(2) to control EtO and chloroprene emissions. The EPA is not imposing CAA section 112(f)(2) standards to control maleic anhydride, chlorine, acrylic acid, or acrylonitrile in this rulemaking and we found no new information regarding the health effects associated with these pollutants (like the new information on chloroprene and EtO) that would lead us to amend standards for these pollutants under CAA section 112(f)(2). Commenters do not provide any explanation, therefore, of how they are affected or harmed by the EPA analyzing other HAP during this risk review. We have concluded that unacceptable risk posed by emissions from these source categories is driven by emissions of EtO and chloroprene and we imposed additional standards under CAA section 112(f)(2) to reduce emissions of EtO and chloroprene to an acceptable level.

Comment: A commenter argued that given the EPA's failure to articulate a legal basis for its position to conduct a second risk review violates the Agency's obligation to set forth in a proposed rule “the major legal interpretations and policy considerations underlying the proposed rule” according to CAA section 307(d)(3)(c), the commenter did not have adequate notice or an opportunity to comment on this key issue, which plainly is of central relevance to the rule. The commenter asserted that the EPA must supplement the current proposal to provide the required legal analysis and provide a reasonable opportunity for public comment.

Response: The EPA explained in the proposed rule that we were undertaking an updated residual risk review for the SOCMI and Neoprene Production (within the P&R I NESHAP) source categories “due to the development of the EPA's Integrated Risk Information System (IRIS) inhalation unit risk estimate (URE) for chloroprene in 2010” and because “in 2016, the EPA updated the IRIS inhalation URE for EtO.” 88 FR at 25083-84.

The EPA explained that, due to the updated chloroprene information, “the EPA conducted a CAA section 112(f) risk review for the SOCMI source category and Neoprene Production source category. In the first step of the CAA section 112(f)(2) determination of risk acceptability for this rulemaking, the use of the 2010 chloroprene risk value resulted in the EPA identifying unacceptable residual cancer risk caused by chloroprene emissions from affected sources producing neoprene subject to P&R I[.] Consequently, the proposed amendments to P&R I address the EPA review of additional control technologies, beyond those analyzed in the technology review conducted for P&R I, for one affected source producing neoprene and contributing to unacceptable risk.” 88 FR at 25083-84.

Similarly, the EPA explained that, due to updated EtO information, “In the first step of the CAA section 112(f)(2) determination of risk acceptability for this rulemaking, the use of the updated 2016 EtO risk value resulted in the EPA identifying unacceptable residual cancer risk driven by EtO emissions from HON processes. Consequently, the proposed amendments to the HON also address the EPA review of additional control technologies, beyond those analyzed in the technology review conducted for the HON, focusing on emissions sources emitting EtO that contribute to unacceptable risk.” 88 FR at 25084.

The EPA also explained that “even though we do not have a mandatory duty to conduct repeated residual risk reviews under CAA section 112(f)(2), we have the authority to revisit any rulemaking if there is sufficient evidence that changes within the affected industry or significant new scientific information suggesting the public is exposed to significant increases in risk as compared to the previous risk assessments prepared for earlier rulemakings.” 88 FR at 25090. See also 88 FR at 25111 (“Considering all of the health risk information and factors discussed above, particularly the high MIR for both the SOCMI and Neoprene Production source categories, the EPA proposes that the risks for both source categories are unacceptable. . . . [W]hen risks are unacceptable, under the 1989 Benzene NESHAP approach and CAA section 112(f)(2)(A), the EPA must first determine the emissions standards necessary to reduce risk to an acceptable level, and then determine whether further HAP emissions reductions are necessary to provide an ample margin of safety to protect public health or to prevent, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect.”).

Finally, the scientific and technical bases for the EPA's proposed action are voluminously presented in the numerous supporting memoranda contained in the public docket for the proposed rulemaking. See, e.g., the documents titled Residual Risk Assessment for the SOCMI Source Category in Support of the 2023 Risk and Technology Review Proposed Rule; Residual Risk Assessment for the Polymers & Resins I Neoprene Production Source Category in Support of the 2023 Risk and Technology Review Proposed Rule; Analysis of Control Options for Process Vents and Storage Vessels to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Equipment Leaks to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Heat Exchange Systems to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Wastewater Streams to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Flares to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Process Vents and Storage Vessels to Reduce Residual Risk of Chloroprene Emissions at P&R I Affected Sources Producing Neoprene; Analysis of Control Options for Wastewater Streams to Reduce Residual Risk of Chloroprene From Neoprene Production Processes Subject to P&R I; and Analysis of Demographic Factors for Populations Living Near Polymers and Resins I and Polymer and Resins II Facilities (see Docket Item No. EPA-HQ-OAR-2022-0730-0085, -0095, -0074, -0003, -0071, -0087, -0070, -0083, -0092, and -0060, respectively). Also see the documents titled Analysis of Demographic Factors for Populations Living Near Hazardous Organic NESHAP (HON) Operations—Final; Analysis of Demographic Factors for Populations Living Near Hazardous Organic NESHAP (HON) Operations: Whole Facility Analysis—Final; Analysis of Demographic Factors for Populations Living Near Neoprene Production Operations—Final; and Analysis of Demographic Factors for Populations Living Near Neoprene Production Operations: Whole Facility Analysis—Final, which are available in the docket for this rulemaking.

The EPA clearly did articulate its legal position in a manner that was sufficient to provide the public a meaningful opportunity to comment on the basis for its action, as evidenced by the EPA's receipt of comments from several commenters discussing the EPA's use of its CAA section 112(f)(2) authority to conduct an updated residual risk review and discussing the merits of the risk review. As explained in this section, commenters argued on both sides: that the EPA did not have authority to conduct the risk review in this rule, or that the EPA must conduct additional risk reviews during every 112(d)(6) technology review. (See other responses above in this section of this preamble.) While comments may not provide the only evidence that a point was adequately noticed, “insightful comments may be reflective of notice and may be adduced as evidence of its adequacy.” Horsehead Dev. Co. v. Browner, 16 F.3d 1246 (D.C. Cir. 1994); Nat'l Rest. Ass'n v. Solis, 870 F. Supp. 2d 42, 52-53 & n.6 (D.D.C. 2012). With thoughtful comments from both sides of the issue received here, the EPA has met this test.

d. HON Rule Changes Related To EtO

i. Process Vents and Storage Vessels in EtO Service

Comment: A commenter said that they supported the EPA's proposed definition for “in ethylene oxide service” for process vents and the sampling and analysis procedures for owners and operators to demonstrate that each process vent does, or does not, meet the definition. However, other commenters requested the following clarifications or revisions to the proposed text:

• the EPA should revise the definition of “in ethylene oxide service” and the corresponding procedures in40 CFR 63.109(a) for determining whether a process vent is in EtO service so that the corresponding 1 ppmv cut-off for process vents in the definition of “in ethylene oxide service” applies on an annual average basis. The commenter provided numerous examples showing that EtO concentration in the process or the vent stream can vary over time depending on what material is being produced.
• the EPA should clarify that the 5 lb/yr EtO mass emission rate limit for combined process vents as specified in40 CFR 63.113(j)(2), 40 CFR 63.124(a)(4) and (a)(4)(iii), and within the definition of “in ethylene oxide service” should be on a CMPU-by-CMPU basis.
• the EPA should clarify at40 CFR 63.109(a) that the location to measure the EtO concentration for process vents should be after the last recovery device (if any recovery devices are present) but prior to the inlet of any control device that is present and prior to release to the atmosphere to be consistent with requirements elsewhere in the HON ( e.g., see 40 CFR 63.115(a)).

Commenters requested that the EPA revise the concentration threshold for process vents from 1 ppmv to 3 ppmv or greater and only require additional control of process vents that total 100 pounds per year or more on an affected source basis. The commenters argued these thresholds would alleviate detection limit challenges; and that process vents with concentrations and mass emissions rates below these thresholds do not significantly contribute to unacceptable risk. A commenter pointed out that moisture and interferents will prevent obtaining measurements down to 1 ppmv in certain streams such as those associated with vacuum distillation operations where motive force is provided by steam jet exhaust, and the emission point contains primarily steam with potentially trace levels of organic HAP, or in streams at the inlet to control devices.

Response: We acknowledge a commenter's support of the definition for “in ethylene oxide service” for process vents and the procedures for owners and operators to demonstrate that process vent does, or does not, meet the definition. However, we are not revising the definition in the final rule as requested by other commenters such that it applies on an annual average basis. We also disagree with the commenters' request to revise the concentration threshold for process vents from 1 ppmv to 3 ppmv or greater and only require additional control of process vents that total 100 pounds per year or more on an affected source basis.

While we agree that the EtO concentration in the process or the vent stream can vary over time depending on what material is being produced, we consider the corresponding 1 ppmv EtO cut-off for process vents reasonable in terms of being measurable and quantifiable, and also appropriate for the vent stream characteristics we intended to regulate that resulted in risk reductions. We acknowledge every facility is different. Some facilities may pose less risks than others, but in a densely populated area with a nearby receptor and under specific conditions, the risks could none-the-less be unacceptable. In order to be protective of public health, we took a conservative approach.

We note that several facilities reported (in response to our CAA section 114 request) EtO measurements below 1 ppm; one of these measurements is equivalent to greater than 0.5 lb/hr and all other measurements below 1 ppm exhibited mass rates less (sometimes much less) than 0.02 lb/hr. Given that there do not appear to be detection limit challenges based on this recent stack test data, we disagree with the commenters' assertion that there is a need to alleviate detection limit challenges. Additionally, the 1 ppmv undiluted EtO threshold is also used in the Miscellaneous Organic Chemical Manufacturing NESHAP (MON) and we are not aware of any detection limit issues within that source category.

With regard to a commenter's request that the 5 lb/yr EtO mass threshold for combined process vents be on a CMPU-by-CMPU basis, we agree that this was our intent; therefore, we have clarified this in the final rule at 40 CFR 63.113(j)(2), 40 CFR 63.124(a)(4) and (a)(4)(iii), and within the definition of “in ethylene oxide service.” Finally, as requested by a commenter, we have clarified at 40 CFR 63.109(a)(3) that the sampling site shall be after the last recovery device (if any recovery devices are present) but prior to the inlet of any control device that is present and prior to release to the atmosphere.

Comment: Commenters said that they supported the EPA's proposed definition for “in ethylene oxide service” for storage vessels and the sampling and analysis procedures for owners and operators to demonstrate that each storage vessel does, or does not, meet the definition. However, some commenters requested the following clarifications or revisions to the proposed text:

• the EPA should revise the definition of “in ethylene oxide service” so that the corresponding the 0.1 percent by weight threshold for storage vessels in the definition of “in ethylene oxide service” applies on an annual average basis. The commenter pointed out that this is already allowed for equipment leaks at40 CFR 63.109(c)(1); therefore, the EPA could amend the language in 40 CFR 63.109(b) to consistent with 40 CFR 63.109(c).
• the EPA should add more flexibility to the alternative approach in40 CFR 63.109(b)(2) to allow for good engineering judgment and process knowledge similar to the language in 40 CFR 63.109(c)(2) for equipment leaks.
• the EPA should revise the definition to refer to “the procedures specified in § 63.109” instead of “sampling and analysis” to reduce confusion and eliminate the potential safety risks/costs of unnecessary sampling; it is not until proposed40 CFR 63.109(b)(2) that the reader is informed that one is allowed to use information specific to the stored fluid to calculate the concentration of E.O., which does not necessitate sampling.

A commenter also pointed out that the EPA's proposed definition does not comport with the definition discussed in the Agency's memorandum which states: “For storage vessels of any capacity and vapor pressure, “in ethylene oxide service” means that the concentration of ethylene oxide within the tank liquid is greater than or equal to 1 ppmw. These definitions exclude ethylene oxide that is present as an impurity . . .” (see Docket Item No. EPA-HQ-OAR-2022-0730-0074). The commenter requested that the EPA confirm the threshold for storage vessels is 0.1 percent by weight, as stated in the red-line strike-out version of the proposed rule text, and that the proposed definition should not include the phrase: “The exemption for “vessels storing organic liquids that contain organic hazardous air pollutants only as impurities” listed in the definition of “storage vessel” in this section does not apply for storage vessels that may be in ethylene oxide service.” Commenters added that the EPA should properly justify the 0.1 percent by weight threshold, or revise the threshold to eliminate unnecessary additional control of sources that do not pose unacceptable risk. The commenters asserted that the risks attributable to storage vessels are those storing high concentrations of EtO, not vessels storing low concentration materials, making the EPA's proposed 0.1 percent by weight threshold arbitrary. To address the unnecessary burden imposed by the EPA's proposal, the commenters requested the EPA revise its analysis such that only those storage vessels that significantly contribute to risk ( i.e., those storing 100 percent EtO) be subject to additional control requirements for EtO.

Response: The EPA acknowledges a commenter's support of the definition for “in ethylene oxide service” for storage vessels and the procedures for owners and operators to demonstrate that each storage vessel does, or does not, meet the definition. However, we are not revising the definition in the final rule as requested by other commenters such that it applies on an annual average basis; these commenters did not provide justification for why this revision is needed. We are finalizing the definition as proposed such that a storage vessel is considered in EtO service anytime it is storing a liquid that is at least 0.1 percent by weight of (or 1,000 ppmw) EtO. We consider the 0.1 percent by weight of EtO threshold reasonable in terms of being measurable and quantifiable, and also appropriate for the vent stream characteristics we intended to regulate that resulted in risk reductions. We acknowledge every facility is different. Some facilities may pose less risks than others, but in a densely populated area with a nearby receptor and under specific conditions, the risks could none-the-less be unacceptable. In order to be protective of public health, we took a conservative approach. We note that a 1,000 ppmw threshold corresponds to the chemical inventory reporting requirements under the Emergency Planning and Community Right-to-Know Act and other supplier notification requirements, so facilities should have knowledge of the amount of EtO stored from these sources.

Regarding the inconsistency between language used in docket item EPA-HQ-OAR-2022-0730-0074 versus language used in the red-line strike-out version of the proposed rule text, we have determined that the language used in docket item EPA-HQ-OAR-2022-0730-0074 is an error. In other words, we are finalizing the red-line strike-out version of the proposed rule text such that the definition does include the phrase: “The exemption for “vessels storing organic liquids that contain organic hazardous air pollutants only as impurities” listed in the definition of “storage vessel” in this section does not apply for storage vessels that may be in ethylene oxide service.” While we believe that emissions from vessels storing impurity levels of EtO are very low and do not result in additional risk, we are not providing additional constraints or clarifications on the determination of the threshold ( e.g., providing averaging times) because we anticipate that the Emergency Planning and Community Right-to-Know Act and supplier notifications will generally be the basis for applicability determinations.

Also, we disagree with the commenters' request to add more flexibility to the alternative approach in 40 CFR 63.109(b)(2) for storage vessels to be consistent with the equipment leaks provision at 40 CFR 63.109(c). We believe the rule is already clear regarding determining whether storage vessels are “in ethylene oxide service.” In order to determine the requirements for storage vessels in EtO service, facilities must look at both the definition of “in ethylene oxide service” and the requirements in 40 CFR 63.109 together. The definition of “in ethylene oxide service” lets the owner or operator designate a storage vessel based on process knowledge; however, if an owner or operator wants to say a storage vessel is not in EtO service, they must use the procedures in 40 CFR 63.109(b). The rule at 40 CFR 63.109(b)(2) already explicitly allows an avenue for an owner or operator to calculate the concentration of EtO of the fluid stored in the storage vessels if information specific to the fluid stored is available which includes data based on safety data sheets.

With regard to a commenter's request to change the phrasing of “sampling and analysis is performed as specified in § 63.109” to “the procedures specified in § 63.109 are performed” within the definition of “in ethylene oxide service” for storage vessels, we agree this suggested language is more clear and have revised it in the final rule.

Comment: A commenter said they support the EPA's proposed rule text at 40 CFR 63.113(j) that requires owners and operators to reduce emissions of EtO from process vents in EtO service by either: (1) Venting emissions through a closed-vent system to a control device that reduces EtO by greater than or equal to 99.9 percent by weight, to a concentration less than 1 ppmv for each process vent, or to less than 5 lb/yr for all combined process vents; or (2) venting emissions through a closed-vent system to a flare meeting the proposed operating and monitoring requirements for flares in NESHAP subpart F. The commenter also said they support the EPA's proposed rule text at 40 CFR 63.119(a)(5) that requires owners and operators to reduce emissions of EtO from storage vessels in EtO service by either: (1) Venting emissions through a closed-vent system to a control device that reduces EtO by greater than or equal to 99.9 percent by weight or to a concentration less than 1 ppmv for each storage vessel vent; or (2) venting emissions through a closed-vent system to a flare meeting the proposed operating and monitoring requirements for flares in NESHAP subpart F.

However, other commenters argued that the EPA should disallow the use of flares to control EtO from process vents and storage vessels given that flares can only reduce EtO emissions by, at most, 98.6 percent; and therefore, cannot meet the proposed 99.9 percent by weight EtO reduction requirement. The commenters contended that the EPA arbitrarily and unlawfully assumes HON sources will use non-flare control devices instead of flares to reduce EtO from process vents and storage vessels. The commenters added that the Agency's supposition that it is “likely” that sources will not use flares given the flare cap provides no rational or substantial basis for assuming 99.9 percent destruction of EtO from process vents and storage vessels. A commenter contended that the difference between using a flare and a non-flare control device to reduce emissions of EtO from process vents and storage vessels could be significant, and provided an example using an emissions inventory from 2021 for Indorama's Port Neches plant showing this. A commenter asserted that requiring HON sources to use non-flare controls (and disallowing the use of flares) to control EtO from process vents and storage vessels would not result in additional costs beyond those that the EPA has already predicted, since the EPA's cost-effectiveness analysis assumed that all 12 HON facilities that need to control EtO from process vents and storage vessels to reduce risk to acceptable levels would install thermal oxidizers.

The commenters added that unlike the HON, the EPA in its risk proposal for Neoprene Production processes subject to the P&R I NESHAP (appropriately) proposes to require use of non-flare controls that reduce chloroprene by 99.9 percent. The commenters asserted that if the EPA were to finalize its proposal to allow HON sources to use flares to reduce EtO from process vents and storage vessels (and thus allow destruction efficiencies lower than 99.9 percent), this differing treatment of risk-driving HAPs from HON and P&R I vents and storage vessels would render the Agency's final rule arbitrary and capricious.

Response: We acknowledge a commenter's support for 40 CFR 63.113(j) and 40 CFR 63.119(a)(5). We also disagree with other commenters' assertions that the EPA must prohibit the use of flares to control EtO from process vents and storage vessels. In the proposed rule, we recognized flares cannot achieve 99.9 percent EtO reduction and proposed an EtO flare load limit. We also noted that as part of the CAA section 114 request, six facilities measured EtO emissions from their EtO emission points and none of these six facilities currently use a flare to control EtO emissions from process vents or storage vessels. Even so, our modeling file does include several other HON facilities that do use flares to control process vents and storage vessels that emit EtO. Therefore, we accounted for these flares operating at 98 percent EtO reduction in our risk assessment, proposed an EtO flare load limit, and determined that it is not necessary for flares to achieve 99.9 percent EtO reduction in order to reduce risk to an acceptable level and provide an ample margin of safety to protect public health (provided that owners and operators still comply with the entire suite of EtO control requirements that we are finalizing in the rule). However, in response to a comment addressed in section IV.A.3.d.v of this preamble we are not including an EtO flare load limit in the final rule; and we determined that risks are acceptable for flares operating at 98 percent EtO reduction and flares operating at 98 percent EtO reduction provide an ample margin of safety to protect public health, without the need for an EtO flare load limit.

Also, to the commenter's assertion that the EPA is giving differing treatment between HON process vents and storage vessels and P&R I process vents and storage vessels, we note that in the final rule, we require use of non-flare controls to reduce chloroprene by 98 percent ( i.e., we prohibit the use of flares to control chloroprene in the Neoprene Production source category) because dioxins and furans can be formed when chlorinated compounds ( i.e., chloroprene) are present and combusted, and the more consistent combustion of non-flare controls such as thermal oxidizers is more appropriate than flares to reduce dioxin and furan formation. Dioxin and furan formation is not a concern when combusting EtO in a flare.

ii. Equipment Leaks in EtO Service

Comment: A commenter said that they supported the EPA's proposed definition for “in ethylene oxide service” for equipment leaks and the sampling and analysis procedures for owners and operators to demonstrate that process equipment does, or does not, meet the definition. However, some commenters requested the EPA revise the 0.1 percent by weight threshold to 5.0 percent by weight.

A commenter argued that most of EtO emissions from equipment leaks come from piping that has an EtO concentration of 5.0 percent by weight or higher. The commenter contended that expanding the new regulatory provisions to streams containing EtO between 0.1 and 5.0 percent by weight will result in a much more stringent LDAR program for components that are primarily in ethylene, methane, nitrogen, and carbon dioxide (CO₂) service, and will have a minimal to negligible impact on reducing the fugitive emissions of EtO and the resulting residual risk. The commenter also recommended that the EPA revise 40 CFR 63.109(c)(1) and (2) to reflect the 5.0 percent by weight threshold instead of the 0.1 percent by weight threshold.

Other commenters asserted that the EPA does not explain why a 0.1 percent by weight threshold of EtO in equipment presents unacceptable risk; the commenters said based on their revised risk modeling assessment (including their recommended revisions to the HEM4 modeling file inputs such as revised flare parameterization, updates provided by companies, and removal of one time/infrequent release events), equipment containing less than 5 percent EtO does not significantly contribute to risk, nor is it cost-effective when considered in the context of an ample margin of safety analysis.

A commenter added that the EPA should revise the definition to refer to “the procedures specified in § 63.109” instead of “sampling and analysis” to reduce confusion and eliminate the potential safety risks/costs of unnecessary sampling; it is not until proposed 40 CFR 63.109(c)(2) that the reader is informed that one is allowed to use engineering judgment to determine the EtO concentration of the process fluid, which does not necessitate sampling.

Response: The EPA acknowledges a commenter's support of the definition for “in ethylene oxide service” for equipment leaks and the procedures for owners and operators to demonstrate that process equipment does, or does not, meet the definition. However, we reject other commenters' requests to revise the 0.1 percent by weight threshold to 5.0 percent by weight. As discussed in the preamble to the proposed rule (see 88 FR 25080, April 25, 2023), results from our risk assessment indicate that, for the source category MIR of 2,000-in-1 million, approximately 20 percent is from emissions of EtO related to HON equipment leaks. We also note that the risk from EtO from HON equipment leaks at seven facilities (including the facility driving the MIR) is ≥100-in-1 million. To help reduce the risk from the SOCMI source category to an acceptable level, for EtO emissions from HON equipment leaks, we performed a review of available measures for reducing EtO emissions from components that are most likely to be in EtO service, which include connectors (in gas and vapor service or light liquid service), pumps (in light liquid service), and valves (in gas or light liquid service). Almost all EtO emissions related to equipment leaks come from these three pieces of equipment.

We considered the proposed 0.1 percent by weight threshold reasonable in terms of being measurable and quantifiable, and also appropriate for the vent stream characteristics we intended to regulate that resulted in risk reductions. We acknowledge every facility is different. Some facilities may pose less risks than others, but in a densely populated area with a nearby receptor and under specific conditions, the risks could none-the-less be unacceptable. In order to be protective of public health, we took a conservative approach. Regarding comments that there is no justification for adding additional controls for low risk sources given the cost, in codifying the Benzene NESHAP approach CAA section 112(f)(2) does not allow us to consider cost at the first step of the residual risk analysis in identifying what standards are needed to reduce unacceptable risk to an acceptable level, and at proposal, and in the final rule, we determined that prior to application of the control requirements being finalized, the risk was unacceptable. It is only if the EPA adopts more stringent standards to further reduce emissions and reduce risks below acceptable levels if needed to provide an ample margin of safety to protect public health, at the second step of the residual risk analysis, that costs may be considered among other relevant factors.

With regard to a commenter's request to change the phrasing of “sampling and analysis is performed as specified in § 63.109” to “the procedures specified in § 63.109 are performed” within the definition of “in ethylene oxide service” for equipment leaks, we agree this suggested language is more clear and have revised it in the final rule.

Comment: Several commenters objected to the EPA's proposal at 40 CFR 63.171(f) that does not allow delay of repair for equipment in EtO service.

Commenters contended that the EPA did not consider the cost associated with more frequent and/or longer outage times due to removal of the delay of repair option. Commenters stated that most valves and connectors are not configured with in-line spares; and if a repair requires replacement of a leaking component, the equipment must be isolated, and in certain instances the entire process unit must be shutdown. Commenters contended that additional shutdowns directly increase the likelihood of future leaks given that each shutdown and startup cycle subjects equipment to pressure and temperature changes that could negatively impact equipment reliability.

Commenters added that, often, valves or other connectors may not be “off the shelf” so that a facility would be required to special order and wait on the equipment to arrive while shutdown. A commenter stated that lead up times to shutdowns typically provide adequate time for facilities to order and test components; however, if the delay of repair provisions are eliminated, required lead times for these activities will result in extended shutdowns. The commenter also said that facilities must often carefully evaluate the safety considerations of “boxing in” leaking EtO equipment due to the tendency of stagnant EtO to polymerize which can render equipment such as control valves inoperable. The commenter continued that it is often necessary to evaluate and engineer a clamp style solution, a process that can take more than the allotted 15-day repair time.

Commenters also noted additional consequences of more frequent shutdowns including additional wear on rotating equipment, and reduced catalyst life which could result in emission increases and waste generation.

A commenter argued that eliminating delay of repair would generally require a first repair attempt within 5 days of detection, which is an infeasibly short amount of time to safely shutdown one process unit, much less multiple integrated units. The commenter stated that delay of repair provides facilities with time needed to plan and prepare for a shutdown, which minimizes the safety risks that inevitably accompany shutdowns and startups. The commenter added that being required to shutdown abruptly and more frequently will unnecessarily increase safety risks to employees with minimal environmental benefit. The commenter said that they follow standard industry procedures in preparing for a scheduled shutdown, which involves adequate preparation time and personnel to completely purge of all lines containing EtO, using appropriate controls, before shutdown. The commenter said that stagnant EtO polymerizes, creating heat that can cause explosions.

Commenters argued that an increase in number of shutdowns due to the EPA eliminating delay of repair for equipment in EtO service could also result in impact to supply chain. A commenter said that supply chain disruptions pose significant economic, security and health risks. Another commenter added that impacts on supply could well impact broader EPA and Administration priorities such as the EPA's recent proposal to electrify motor vehicles which is dependent upon EV battery production (and such battery production is currently generally dependent upon ethylene carbonate, which is produced by reacting EtO with CO₂).

Commenters contended that the EPA failed to explain how eliminating delay of repair for equipment in EtO service would reduce EtO emissions or risks. Commenters argued that eliminating the delay of repair provisions results in an increase in emissions due to more frequent shutdowns. Commenters contended that without the ability to delay repair, it will result in unplanned shutdowns which will result in greater emissions as emissions are expected to be higher during shutdown than emissions from components on delay of repair. A commenter said EtO emissions can range from approximately 5 to 340 lbs per shutdown event and provided calculations showing that a repair of a leaking valve would have to be delayed for over 10 years before the emissions exceeded those generated by a CMPU shutdown that resulted in 85 lbs of EtO emissions. Some commenters pointed out that delay of repair provisions allow facilities to assess whether allowing a small leak to continue poses less risk and concern than the emissions necessarily associated with a shutdown.

A commenter argued that they would expect only a small number of component(s) in EtO service to use the delay of repair provisions at 40 CFR 63.171 given that HON CMPUs that produce and use EtO as a raw material will typically have a planned process shutdown every 2 to 3 years depending on the specific process.

Another commenter suggested that the EPA adopt the TCEQ delay of repair program as described in 30 Texas Administrative Code (TAC) 115.352(2): If the repair of a component within 15 days after the leak is detected would require a process unit shutdown that would create more emissions than the repair would eliminate, the repair may be delayed until the next scheduled process unit shutdown. The commenter argued that the TCEQ requirement is reasonable given that it allows companies to choose the lowest-emitting option and attain the goal of minimizing emissions.

Response: Regarding commenters' assertions about cost and timing of repair, with one exception, we are finalizing the proposed requirements for delay of repair for equipment in EtO service pursuant to CAA section 112(f)(2), on the basis of risks being unacceptable. Where we find risks are unacceptable, the EPA must determine the emissions standards necessary to reduce risk to an acceptable level. The largest contributor to risk from EtO facilities is due to emissions from equipment leaks. Because emissions of EtO from the SOCMI source category result in unacceptable risks, we proposed and are finalizing requirements that would reduce risks to an acceptable level, including provisions not allowing a delay of repair for equipment in EtO service. Allowing delay of repair would allow increased emissions of EtO and increased risk. The one exception is that we are revising 40 CFR 63.171(b) to allow a delay of repair for equipment if the equipment is isolated from the process and does not remain in organic HAP service.

To the commenters' assertions that increased startup and shutdown events will lead to additional EtO emissions, we disagree. First, we have removed the exemptions for periods of SSM. As a result, facilities must be in compliance with the rule requirements at all times and must control EtO emissions at all times. Therefore, while there may be additional EtO entering the control device as a result of SSM, the finalized control provisions ensure risk remains acceptable. Second, we are finalizing maintenance vent requirements which are intended to address equipment openings that result from startup, shutdown, maintenance, or inspection of equipment where equipment is emptied, depressurized, degassed, or placed into service. We are finalizing that owners and operators may not release more than 1.0 ton of EtO from all maintenance vents combined per any consecutive 12-month period. An owner or operator may designate any process vent as a maintenance vent if the vent is only used as a result of startup, shutdown, maintenance, or inspection of equipment where equipment is emptied, depressurized, degassed, or placed into service. Thus, shutdowns resulting from the identification of leaks could be included under the 1.0 tpy EtO limit. It is the responsibility of the owner or operator to plan accordingly for equipment replacement and minimizing safety risks during shutdowns. Third, using the commenters' estimates of EtO emissions ranging from 5 to 340 lbs per shutdown event, the number of shutdowns that could fall under the 1 tpy limit could range from almost 6 to 400. Given the typical leak rates seen by industry (as discussed in our responses to comments in section 2.2 of the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking) and the variety of process conditions, the EPA believes that it would be unlikely for a facility to develop 5 leaks at the maximum estimated EtO levels warranting shutdown events. We note that even if a facility were to reach the 1.0 tpy maintenance vent limit, they may still shutdown to repair leaking equipment so long as the emissions are controlled.

Comment: In response to the EPA soliciting comments on alternative monitoring technologies, a commenter supported optical gas imaging (OGI) be used as an option to find larger equipment leak air emissions and to repair leaks, and that perhaps it could be used in conjunction with an annual connector monitoring program for connectors in EtO service. Another commenter contended that the EPA failed to include LDAR alternatives for use of OGI despite the agency's recognition of its efficacy in the recent NSPS subpart OOOOb and EG subpart OOOOc proposed rules and development of Appendix K, which specifically states it is the methodology that the EPA plans to incorporate by reference in the different NSPS/NESHAP subparts to enable implementation of this technology. The commenter contended that the EPA should correct this inconsistency. A commenter recommended that if the EPA determines OGI is an appropriate option to include in the final rule, the EPA model the specific OGI requirements after those contained in NSPS subpart OOOOa at 40 CFR 60.5397a(c)(7) and (d)(1) that address fugitive emissions monitoring plans where OGI is used and the requirements in 40 CFR 60.5397a(h)(4)(iv) that address resurveying equipment to verify repair. The commenter noted that some of the requirements in NSPS subpart OOOOa relative to OGI monitoring will need to be adjusted to account for application of OGI to a CMPU and not an oil and gas production site, as there are more potential interferences in a CMPU.

Another commenter contended that the EPA has not clearly addressed the use of any alternative work practices for fugitive monitoring such as OGI but is soliciting technical justification to include or exclude OGI as an option for the proposed low (100 ppmv) detection levels using EPA Method 21. The commenter added that this low concentration has not been evaluated as a level which can be observed reliably and consistently with an OGI camera. The commenter requested that any technical evaluation and proposed outcome be re-published as a proposal to ensure comprehensive evaluation by all potentially affected parties and authorities. The commenter concluded that the EPA should not collect comments, complete a review, and make a final rule change without further opportunity for comment.

A commenter stated that based on publicized research, including the EPA's Optical Gas Imaging Appendix K Technical Support Document, there is a known variability of response factors within chemical plant gas streams and the detection/sensitivity ranges of OGI technology versus legacy technologies. The commenter noted that case-by-case permits have been issued with an OGI alternative; however, each of these permits has incorporated an annual EPA Method 21 survey to ensure that all components have been properly evaluated for leaks, and the commenter recommended adding this requirement for any OGI alternative for these sites.

A commenter noted that the results obtained using OGI for leak detection can be heavily influenced by instrument performance, environmental conditions, and human factors. The commenter explained that weather conditions such as ambient temperature, wind speed, or wind direction relative to the observer may affect the apparent concentration of any leak when viewed with OGI. The commenter stated that a study of OGI for detection of natural gas leaks found that only 51 percent of leaks were detected at wind speeds above 21 miles per hour. The commenter opined that higher concentrations of gas streams may be needed for detection to occur with OGI technology, especially as it applies to OGI surveys within the chemical sector, whereas the annual EPA Method 21 survey ensures a quantitative measurement and more appropriately demonstrates compliance. The commenter requested the EPA clarify if it plans to include the proposed Appendix K or another monitoring protocol for OGI to be followed so that there are clear and consistent expectations of field experience for camera operators including operator training, component dwell time, required operator breaks, and other criteria which are not addressed in 40 CFR 63.11.

Response: We disagree with the commenters that stated the rules should have required the use of OGI. The SOCMI has been complying with equipment leak regulations since the early 1980s, and leaks are much smaller than those found in the oil and gas industry. As a result, the leak definitions that SOCMI facilities are complying with are in the area of 500 to 1000 ppm for most equipment, and the proposed and final rule lowers leak definitions to 100 ppm for valves and connectors in EtO service. We acknowledge that OGI is effective at finding large leaks quickly for many compounds. OGI is less effective at finding low-level leaks, especially in the environmental conditions that generally exist during a field survey. As a commenter indicated, the low leak concentrations that were proposed and which we are finalizing (100 ppm) have not been evaluated at a level which can be observed reliably and consistently with an OGI camera. In feasibility studies conducted as part of the development of 40 CFR part 60 appendix K, which are the procedures for using OGI in leak detection, leaks below 500 ppm (or even higher in some circumstances) could not be reliably detected even in a laboratory setting except under the most ideal conditions. We also agree with the commenter who noted that leak detection with an OGI camera is heavily influenced by environmental conditions and human factors. Additionally, as explained more fully in response to a comment in section IV.B.3.b.ii of this preamble, OGI cameras, especially in the most common filter bandwidths, are not sensitive to some of the chemicals found at SOCMI facilities, which can make leaks difficult or even impossible to see, even for large leaks. In promulgating NSPS subpart OOOOb and EG subpart OOOOc, the EPA considered the level of control required for fugitive emissions in the oil and natural gas sector, as well as the chemical make-up of the expected fugitive emissions. Based on those considerations, we determined that OGI was a viable option for facilities subject to regulation under those subparts through our BSER analysis. However, for the reasons outlined in this response, while the use of OGI is appropriate for the oil and natural gas sector, it would not be appropriate to rely exclusively upon OGI for the SOCMI source category.

iii. Heat Exchange Systems in EtO Service

Comment: A commenter said that they supported the EPA's proposed definition for “in ethylene oxide service” for heat exchange systems and the sampling and analysis procedures for owners and operators to demonstrate that each heat exchange system does, or does not, meet the definition. However, commenters requested the following clarifications or revisions to the proposed text:

• the EPA should add into the definition an exclusion for EtO present as an impurity consistent with the Agency's memorandum which states: “This definition excludes ethylene oxide that is present as an impurity.” (see Docket Item No. EPA-HQ-OAR-2022-0730-0074).
• the EPA should revise40 CFR 63.109(e) to allow the ability to use good engineering judgment to determine the percent of EtO in the process fluid as they have for equipment leaks in 40 CFR 63.109(c)(2). The commenters said that process fluids serviced by heat exchange systems are the same process fluids contained in equipment that must be evaluated for “in ethylene oxide service,” and this prohibition negates the cost savings and flexibility allowed by the use of good engineering judgment for equipment leaks because facilities will be required to conduct sampling and analysis on the same process streams regardless under the heat exchange system provisions. The commenters added that sampling and analyzing process fluids subject to the monitoring requirements for heat exchange systems presents the same issues and difficulties that the EPA identified as the basis for allowing engineering judgment under the MON RTR.
• the EPA should consider allowing facilities to account for site-specific conversion of EtO to ethylene glycol in water in heat exchange systems based on the characteristics (e.g., temperature and pH) of the heat exchange system in determining the threshold definition.

Some commenters requested the revise the 0.1 percent by weight threshold to at least 0.5 percent by weight. These commenters argued that a heat exchanger with an industry-average flow rate with a leak rate of 3.6 ppmw and a process fluid concentration of 0.5 percent EtO would not pose unacceptable risk if the leak were to occur for 135 days as allowed by the existing heat exchange system monitoring provisions ( i.e., quarterly sampling plus a 45-day repair period). A commenter asserted that the EPA does not explain why a 0.1 percent by weight threshold of EtO in process fluid presents unacceptable risk.

Response: We acknowledge the commenter's support of the definition for “in ethylene oxide service” for heat exchange systems and the procedures for owners and operators to demonstrate that each heat exchange system does, or does not, meet the definition. However, we disagree with other commenters' requests to revise the 0.1 percent by weight threshold to at least 0.5 percent by weight. We consider the 0.1 percent by weight threshold reasonable in terms of being measurable and quantifiable, and also appropriate for heat exchange system leak characteristics we intended to regulate that resulted in risk reductions. We acknowledge every facility is different. Some facilities may pose less risks than others, but in a densely populated area with a nearby receptor and under specific conditions, the risks could none-the-less be unacceptable. In order to be protective of public health, we took a conservative approach.

We agree to the commenter's request to allow the ability to use good engineering judgment at 40 CFR 63.109(e) to determine the percent of EtO of the process fluid cooled by the heat exchange system similar to what we have allowed for equipment leaks in 40 CFR 63.109(c)(2). We are making this change in the final rule due to the difficulty and issues with sampling and testing fluid in process lines, particularly if the fluid contains EtO. Also, we believe the use of site-specific conversion calculations of EtO to ethylene glycol in heat exchange systems already qualifies as good engineering judgment using calculations based on process stoichiometry; however, due to its relation to risk as previously discussed, the threshold for determining if equipment is “in ethylene oxide service” is not being revised per the commenter's request.

Regarding the language used in docket item EPA-HQ-OAR-2022-0730-0074 versus it not being included in the red-line strike-out version of the proposed rule text, we have determined that the language used in docket item EPA-HQ-OAR-2022-0730-0074 is an error. In other words, we are finalizing the red-line strike-out version of the proposed rule text and are not including an exclusion for EtO present as an impurity. The 0.1 percent by weight threshold already accounts for impurities.

Comment: A commenter said they support the EPA's proposed rule text at 40 CFR 63.104(g)(6) and (h)(6) that requires owners and operators to conduct more frequent leak monitoring (weekly instead of quarterly) for heat exchange systems in EtO service and repair leaks within 15 days from the sampling date (in lieu of the current 45-day repair requirement after receiving results of monitoring indicating a leak in the HON), and delay of repair would not be allowed.

However, other commenters raised the following concerns with regard to sampling frequency and delay of repair. Commenters recommended that the EPA modify the proposed 40 CFR 63.104(g)(6) to require monthly (in lieu of weekly) sampling via the Modified El Paso Method. A commenter contended that weekly monitoring of each heat exchange system will require either multiple sampling apparatuses or frequent movement of the sampling apparatus from one system to another. Similarly, another commenter argued that weekly sampling presents some logistical problems as typically a contractor brings in the monitoring device, which is a skid mounted unit; the contractor will then move the device from one sampling location to additional sampling locations at the site. In some cases, the commenter said that the monitoring skid must be moved to other process areas that are subject to the other rules such as the Ethylene MACT and the MON rule; therefore, a requirement to conduct this type of monitoring on a weekly basis will limit the flexibility to move the monitoring skid at the site.

The commenters suggested that the monthly Modified El Paso Method monitoring could be combined with weekly analysis of a surrogate parameter as an alternative to conducting weekly sampling using the Modified El Paso Method. The commenters said that the surrogate parameter could be something like monitoring weekly using a water analytical method to indicate the presence of a leak or monitoring other parameters that would indicate the presence of a leak; and if a surrogate measurement indicates a leak, the facility would be required to confirm the presence of the leak using the Modified El Paso Method and repair as required by the proposed provisions.

A commenter requested that the EPA not eliminate the option that allows facilities to delay the repair provided emissions from the process shutdown needed to repair the leak are greater than the potential emissions of delaying. The commenter said that this option essentially allows facilities to repair the leak with as little emissions and environmental impact as possible by requiring the facility to evaluate the emissions of a continued leak against the emissions from an entire process shutdown. The commenter claimed that allowing a repair to be delayed until the next process unit shutdown, if emissions from the delay would be less than those from the unplanned shutdown itself, has been a longstanding concept in several chemical sector rules (see for example 40 CFR 60.482-9(c), 63.104(e)(2)(i), 63.171(c), 63.1024(d)(3), and 63.105(d)(3)). The commenter contended that by forcing facilities to repair leaks solely based on a concentration-based threshold, facilities with a smaller recirculation rate will likely emit greater amounts of HAP than if they were allowed to assess the overall mass emissions from the leak versus shutdown and choose the option that minimizes emissions.

The commenter also said that it is unclear why the EPA is proposing to not allow facilities to delay a repair by isolating the equipment such that it is no longer in EtO service. The commenter said that in certain instances, a facility may be able to isolate a leaking heat exchanger but cannot open the equipment until a process unit shutdown.

Response: We acknowledge the commenter's support of the rule text at 40 CFR 63.104(g)(6) and (h)(6) that requires owners and operators to conduct more frequent leak monitoring (weekly instead of quarterly) for heat exchange systems in EtO service and repair leaks within 15 days from the sampling date (in lieu of the current 45-day repair requirement after receiving results of monitoring indicating a leak in the HON), and delay of repair would not be allowed.

However, we disagree with other commenters' request to require monthly (in lieu of weekly) sampling via the Modified El Paso Method. As we stated in the document titled Analysis of Control Options for Heat Exchange Systems to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON (see Docket Item No. EPA-HQ-OAR-2022-0730-0071), we determined baseline EtO emissions and emissions reductions using information the EPA received from Union Carbide Corporation-Seadrift, TX about an EtO emissions event (Incident 293911) that was reported to the TCEQ on October 21, 2018. Using information provided, we calculated different sampling and repair periods required to reduce risks to an acceptable level. Because at least a 90+ percent reduction in EtO emissions is needed to get to this level (as the risk posed by this large leak is at least 400-in-1-million based on current the HON standards and Union Carbide's best case emissions estimates and because other emission sources also contribute to risks), we determined that if the facility identifies and repairs an EtO leak (from a heat exchange system) within 15 days from a weekly sampling event, the facility would achieve a 6.06 tpy EtO emission reduction ( i.e., 93 percent reduction in EtO emissions). Less frequent sampling ( e.g., monthly) and more time to repair the leak from the sampling period does not get to the level of reduction needed to bring facility risk to below 100-in-1 million. We also noted that the facility indicated they are currently conducting weekly sampling for leaks of EtO already and have implemented this type of sampling across all their facilities that have heat exchange systems cooling process streams with EtO.

In addition, we also reject the commenters' request to use a weekly analysis of a surrogate parameter as an alternative to conducting weekly sampling using the Modified El Paso Method. Surrogate methods via water analysis are less sensitive than the Modified El Paso Method. Therefore, though weekly monitoring via a surrogate would catch the largest of leaks, there would still be the potential for leaks to go uncaptured until the next monthly check via the Modified El Paso Method. As a result, to keep risk at an acceptable level, we maintain that weekly monitoring via the Modified El Paso Method is appropriate.

Similarly, we reject a commenter's request to allow delay of repair at 40 CFR 63.104(h)(6) for heat exchange systems in EtO service. As previously discussed, our leak analysis is based on reducing the delay of repair to achieve a cancer risk incidence at or below 100-in-1 million. Given that EtO is a major cancer driver, leaks need to be addressed quickly to keep risk at an acceptable level. Having said this, we agree with the commenter that owners and operators should be allowed to delay a repair by isolating the equipment ( e.g., a heat exchanger) such that it is no longer in EtO service. It was our intent to allow this type of delay of repair which has always been allowed in the HON at 63.104(e). In this scenario, the owner and operator may delay repair indefinitely as there is no longer an active EtO leak once the equipment is isolated and not in EtO service. For this reason, we are revising 40 CFR 63.104(h)(6) in the final rule to include the following allowance: “Delay of repair of heat exchange systems in ethylene oxide service for which leaks have been detected is allowed if the equipment is isolated from the process such that it is no longer in ethylene oxide service.”

iv. Wastewater in EtO Service

Comment: A commenter said that they supported the EPA's proposed definition for “in ethylene oxide service” for wastewater and the sampling and analysis procedures for owners and operators to demonstrate that each wastewater stream does, or does not, meet the definition. However, other commenters requested the EPA reevaluate the 1 ppmw EtO concentration threshold for wastewater control. These commenters contended that the EPA should make the EtO concentration threshold less stringent ( i.e., a value >1ppmw EtO) primarily on the basis that wastewater should not be regulated more strictly than process vents, there is negligible additional benefit for excessive complexity controlling down to 1 ppmw, and the majority of wastewater collection and treatment emissions will be captured even with a less stringent EtO concentration threshold for wastewater control. The commenters said the EPA does not state why a 1 ppmw threshold is necessary to reduce risks or provide an ample margin of safety, or why Group 1 streams should be classified based solely on this concentration threshold. The commenters recommended the EtO concentration threshold for wastewater control should be changed to an annual average concentration of either 25 or 27 ppmw EtO with an annual average flow rate of 10 liters per minute or higher (in lieu of proposing a no flow rate threshold).

Additionally, commenters requested the EPA establish a mass threshold for wastewater as a “de minimis” value to prevent having to control very small or low flow intermittent wastewater streams that provide little risk reduction, and to raise the concentration commensurate with other rules. A commenter recommended the cutoff for each wastewater stream be a total annual average mass flow rate of EtO to the sewer of at least 0.01 lb/min (0.6 lb/hr). Other commenters requested the EPA add a cutoff such that none of a facility's process wastewater streams should be considered in EtO service if the entire collection of EtO-containing process wastewater streams from HON CMPUs contain no more than 0.24 tpy of EtO. Commenters pointed out that when reviewing the responses to the EPA's CAA section 114 request, typically only one existing Group 2 wastewater stream contributes the majority of the EtO baseload flow to the sewer system; and there are other process wastewater streams in which the EtO concentration is between 1 and 15 ppmw, and the flowrate of the stream is very low or very intermittent, resulting in flows to the sewer systems that are in some cases less than 0.1 lb/hr or even much lower. The commenters argued that it does not make sense to require Group 1 controls for these low volume streams as one is essentially treating almost pure water at this point.

Response: The EPA acknowledges commenters' support and opposition to revise the Group 1 wastewater stream threshold to include wastewater streams in EtO service ( i.e. wastewater streams with total annual average concentration of EtO greater than or equal to 1 ppmw at any flowrate). We are finalizing the definition of “in ethylene oxide service” definition for wastewater as proposed. With regard to the commenters' assertion that the 1 ppmw threshold was not explained, the document titled Analysis of Control Options for Wastewater Streams to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON (see Docket Item No. EPA-HQ-OAR-2022-0730-0087) states that a 1 ppmw threshold is necessary to reduce risk of EtO emissions from wastewater, as the risk due to wastewater is as high as 200-in-1-million, which contributes to unacceptable risk. Additionally, the data from our CAA section 114 request shows that introducing a flowrate threshold, as one commenter suggested, would leave wastewater streams with large amounts of EtO uncontrolled, and could contribute to increased risk at some facilities over 100-in-1-million.

Similarly, we disagree with the commenters' suggestion to include a mass threshold. We calculated the maximum amount of EtO emissions from wastewater streams that would push a facility over the 100-in-1-million mark, and found the lowest amount of excess EtO emissions to be 0.06 tpy. This is well under the commenters' suggestions for a mass threshold.

Comment: A commenter said that they support the proposed provisions at 40 CFR 63.132(c)(1)(iii) and (d)(1)(ii) to revise the Group 1 wastewater stream threshold to include wastewater streams in EtO service ( i.e., wastewater streams with total annual average concentration of EtO greater than or equal to 1 ppmw at any flow rate). However, at least one commenter claimed that there is no need for the proposed provisions at 40 CFR 63.132(c)(1)(iii) and (d)(1)(ii) because the current treatment options for process wastewater streams in EtO service are already adequate to meet the ample margin of safety provided the EPA made one edit to 40 CFR 63.138(e)(1) and (2) when controlling streams with lower concentrations of EtO than previously regulated by the EPA. The commenter recommended that the EPA add an option to both 40 CFR 63.138(e)(1) and (2) that allows the owner or operator to demonstrate compliance with the performance standard for EtO if the outlet concentration of EtO is less than 1 ppmw on an annual average basis. The commenter argued that based on the EPA's proposed definition of “in ethylene oxide service” for wastewater streams it may be difficult to demonstrate a 98- or 99-percent mass removal efficiency for EtO especially if the concentration flowing into the treatment device is a very low concentration; for example, if the inlet flow is 0.1 lb/hr then it may be difficult to demonstrate that the outlet flow is 0.002 lb/hr (98 percent efficiency) or 0.001 lb/hr (99 percent efficiency).

The commenter argued that EtO should only be included on Table 9 to NESHAP subpart G and removed from Table 8 to NESHAP subpart G for the following reasons:

• The EPA provides no basis for adding EtO to Table 8 in the document titled Analysis of Control Options for Wastewater Streams to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON (see Docket Item No. EPA-HQ-OAR-2022-0730-0087).
• The original basis for the compounds listed on Table 8 was that this subset of compounds are very volatile compounds. All the compounds listed on Table 8 have a fraction removed (Fr) value equal to 0.99 as stated in 40 CFR 63.138(e)(2); and the Fr value for EtO as stated in Table 9 is equal to 0.98. Pages 4-9 to 4-10 of the HON Background Information Document (see EPA-453/R-94-003b) provides the original basis for which compounds are included on Table 8 versus Table 9.

• The fraction emitted (Fe) value for the compounds listed on Table 8 range from 0.79 to 1. A value of 1 represents 100 percent of the compound in the wastewater is volatized to the atmosphere; and EtO has a Fe value of 0.5 or only 50 percent is volatilized.

• For new sources,40 CFR 63.132(b)(2) already requires a determination as to whether each wastewater stream requires control for Table 9 compounds by complying with 40 CFR 63.132(c). 40 CFR 63.132(c)(1)(iii) (as proposed) specifies that a wastewater stream is a Group 1 wastewater stream for Table 9 compounds if the wastewater stream contains EtO such that it is considered to be in EtO service.

The commenter argued that the way the group determination procedures are structured, adding EtO to Table 8 (when it is already included as a Table 9 compound) is not going to change the fact that a stream containing more than 1 ppmw EtO is considered to be in EtO service and subject to further treatment and control regardless of whether the source is existing or new.

Response: The EPA acknowledges the commenters' support for and opposition of the proposed wastewater provisions at 40 CFR 63.132(c)(1)(iii) and (d)(1)(ii). We are finalizing these provisions as proposed. We believe the rule is clear with regard to demonstrating compliance with these provisions. A wastewater stream that is less than 1 ppmw EtO is not considered a Group 1 wastewater stream, since it would not meet the Group 1 criteria at 40 CFR 63.132(c)(1)(iii) and (d)(1)(ii), provided it does not meet the criteria at 40 CFR 63.132(c)(1)(i) and (ii), and (d)(1)(i) either.

The EPA does not agree with the commenter that EtO should be removed from Table 8 to NESHAP subpart G. Simply put, the compounds in Table 8 do not biodegrade well and will need to be stripped, while the compounds in Table 9 to NESHAP subpart G can be treated using a biological treatment process. While we acknowledge EtO can be biodegraded (and is included in Table 9), its low Fe value (0.5) suggests that it can only be reduced by half when using a standard biological treatment method, and the remainder would need to be stripped out of the wastewater in order to meet the 1 ppmw threshold. Since we are building on the existing HON standards, we believe it is appropriate to restrict the treatment options given the risk associated with EtO, and have determined facilities will have to use steam stripping to comply with the proposed standards. For these reasons, it is not appropriate to add an option, as requested by the commenter, to both 40 CFR 63.138(e)(1) and (e)(2) that allows the owner or operator to demonstrate compliance with the performance standard for EtO if the outlet concentration of EtO is less than 1 ppmw on an annual average basis regardless of the control method.

However, we agree with the commenter that verifying mass reductions of 99 percent for wastewater streams containing small amounts of EtO may be difficult. As a result, we are providing language in the final rule at 40 CFR 63.138(b)(3) and (c)(3) that allows owners or operators to reduce, by removal or destruction, the concentration of EtO to less than 1 ppmw as determined by the procedures specified at 40 CFR 63.145(b). We believe these revisions add clarity that streams less than 1 ppmw EtO are no longer considered to be “in ethylene oxide service” per the definition and provides unity with the finalized addition of EtO to Table 8 to NESHAP subpart G.

Comment: A commenter recommended that the EPA incorporate the test methods specified in 40 CFR 63.109(d) for analysis of EtO in wastewater directly into 40 CFR 63.144(b)(5)(i) to provide consistency and clarity with the regulation and to avoid the need to prepare additional sampling plans and method validation under 40 CFR 63.144(b)(5)(ii) and (iii). The commenter argued that in order to use the test methods specified in 40 CFR 63.109(d) for determining the annual average concentration of EtO in the wastewater streams ( i.e., EPA Method 624.1 of 40 CFR part 136, appendix A, or preparation by either EPA Method 5031 or EPA Method 5030B and analysis by EPA Method 8260D in the SW-846 Compendium), without the additional cost and effort required to prepare sampling plans and validate the test methods per 40 CFR 63.144(b)(5)(ii) and (iii), these methods listed in 40 CFR 63.109(d) for EtO need to either be added to the list of acceptable methods under 40 CFR 63.144(b)(5)(i) or a cross-reference to 40 CFR 63.109(d) needs to be added to 40 CFR 63.144(b)(5)(i).

In addition, the commenter claimed that depending upon what treatment option is selected in 40 CFR 63.138 to meet the requirements for wastewater streams in EtO service, the test methods and procedures in 40 CFR 63.145(b) for determining compliance with concentration limit standards for non-combustion treatment processes in 40 CFR 63.138(b)(1) and (c)(1) cross-reference the methods specified in 40 CFR 63.144(b)(5)(i). The commenter asserted that by adding the methods specified in 40 CFR 63.109(d) for determining the EtO concentration to the list of acceptable test methods in 40 CFR 63.144(b)(5)(i), the EPA would be also fixing other cross-referencing issues in 40 CFR 63.145 at the same time.

Response: We are revising the final rule in response to the commenter's request to add the test methods specified in 40 CFR 63.109(d) for analysis of EtO in wastewater to 40 CFR 63.144(b)(5)(i). We agree that these test methods are relevant to calculate the annual average concentration of EtO needed to determine Group status, and, by including them, we should create consistency between 40 CFR 63.109(d), 40 CFR 63.144(b)(5)(i), and 40 CFR 63.145.

Comment: A commenter said that they support the proposed provisions at 40 CFR 63.104(k) to prohibit owners and operators from injecting wastewater into or disposing of water through any heat exchange system in a CMPU meeting the conditions of 40 CFR 63.100(b)(1) through (3) if the water contains any amount of EtO, has been in contact with any process stream containing EtO, or the water is considered wastewater as defined in 40 CFR 63.101. On the contrary, other commenters provided suggestions for this prohibition. At least one of these commenters contended that the EPA has not identified any risk associated with EtO-free wastewaters, nor has the EPA otherwise justified why EtO-free wastewaters are prohibited from injection. This commenter said they generally support not allowing waters containing EtO or chloroprene to be added to the cooling loop of a heat exchange system. However, the commenter noted that in the case of the HON and P&R I rules, a wastewater is “water that is discarded” from a CMPU or an EPPU, respectively; therefore, wastewater that is injected into a cooling loop is not discarded water.

Commenters argued the proposed language prohibiting the use of “wastewater” in heat exchange systems is a significant barrier to, if not total prohibition on, water reuse projects that are under consideration at various member facilities. The commenter requested that the EPA modify the prohibition on using “wastewater” in heat exchange systems to make clear that stormwater collected in process areas and treated wastewater from process areas that may include EtO but still qualify for discharge in accordance with a national pollutant discharge elimination system (NPDES) permit may be used in heat exchange systems.

A commenter said that the EPA should add the requirements into the process wastewater prohibition language that already exists in 40 CFR 63.132(f) (rather than include new provisions at 40 CFR 63.104(k)). The commenter claimed that the intent of the prohibition language in 40 CFR 63.132(f) is to prevent discarding a liquid or solid material containing greater than 10,000 ppmw of a Table 9 (to NESHAP subpart G) HAP to water or wastewater unless it is controlled as a Group 1 wastewater; and as currently proposed, a liquid or solid material that is in EtO service, could be discarded to a wastewater stream without control. The commenter urged the EPA to add the following sentence to the beginning of 40 CFR 63.132(f): “Owners or operators of each source as defined in § 63.101, beginning no later than the compliance dates specified in § 63.100(k)(11), shall not discard liquid or solid stream containing EtO such that it is considered to be in EtO service, as defined in § 63.101 from a chemical manufacturing process unit to water or wastewater, unless the receiving stream is managed and treated as a Group 1 wastewater stream.” Alternatively, the commenter suggested the EPA could revise the proposed rule text in 40 CFR 63.104(k) in lieu of adding their request sentence to the beginning of 40 CFR 63.132(f).

Response: The EPA acknowledges the commenters' support for and opposition to the proposed provisions that prohibit the injection or disposal of wastewater containing or that has come in contact with EtO, through heat exchange systems. We are finalizing these provisions at 40 CFR 63.104(k) as proposed. We disagree with commenters' requests to allow stormwater or treated wastewater that may contain EtO but qualify for discharge under the NPDES. We note that in a 1980 document titled Water Quality Requirements of the Organic Chemicals Industry for Recycle/Reuse Applications, which is available in the docket for this rulemaking, the potential for increased recycle/reuse for process water in the EtO industry was evaluated. It was found that significant evaporation losses occur from process cooling towers. Any amount of EtO in wastewater sent to cooling towers will inevitably be stripped out and lead to a direct emission event. This is further expanded upon in the preamble to the proposed rule (see 88 FR 25080, April 25, 2023), where we cite emissions events from two HON-subject facilities that reported EtO emissions from heat exchange systems. This was due to combining EtO entrained water with heat exchange water and not due to any heat exchange system leaks, and resulted in ~3 tpy of EtO total emitted. Given the current total risk associated with EtO, allowing any EtO in cooling towers would be unacceptable.

v. EtO Flare Load Limit

Comment: A commenter said that they support the proposed requirement at 40 CFR 63.108(p) that prohibits owners and operators from sending more than 20 tons of EtO to all of their flares combined in any consecutive 12-month period. Other commenters asserted that the EPA must strengthen the monitoring needed to ensure compliance with the EtO flare load limit proposed at 40 CFR 63.108(p). The commenters stated that the requirement that “the owner or operator must keep monthly records of the quantity in tons of ethylene oxide sent to each flare at the affected source and include a description of the method used to estimate this quantity” is left completely up to HON sources to determine how to calculate the amount of EtO sent to their flares. The commenters contended that this cannot ensure compliance with the EtO flare load limit, and thus, cannot ensure that risk is reduced to an acceptable level or that the standards provide an ample margin of safety to protect public health. The commenters asserted that this monitoring requirement is arbitrary and capricious and contrary to CAA sections 112(f) and 114(a)(3). The commenters suggested that the EPA require HON sources to calculate the amount of EtO sent to their flares by: (i) Continuously measuring the flow rate of the waste gas to the flare using a continuous emission monitoring system; (ii) continuously measuring the EtO concentration in the waste gas, also by a continuous emission monitoring system; and (iii) using the data from (i) and (ii) to calculate the actual EtO mass that is sent to the flare over a given time period. The commenters added that this calculation can be done every minute if needed or on an hourly average basis, to provide an accurate mass estimate of the flared EtO.

Numerous other commenters opposed the EtO flare load limit for at least one or more of the following reasons:

• it is unwarranted to impose expensive and stringent EtO limitations on flaring on the entire SOCMI source category subject to the HON when unacceptable risk from EtO flaring is driven by a single facility.
• the proposed cap would be problematic for more than just the flares that the EPA identified given that many owners and operators are currently applying a 99 percent EtO control efficiency to their existing flare operations. TCEQ's control efficiency value for EtO (99 percent) combined with the EPA's determination that EtO emissions of 0.4 tpy would be acceptable (see Docket Item No. EPA-HQ-OAR-2022-0730-0070) would yield a 40 tpy (not 20 tpy) EtO flare load limit.

• when conducting its dispersion modeling for EtO emissions from flares, the EPA did not use the modeling approach used by TCEQ which takes into account the heat release associated with combustion in a flare; TCEQ's modeling approach results in lower off-site impacts from flares, which calls into question whether a cap of flaring is necessary.
• flares have been used to control emissions of HAP for decades.
• the combination of the proposed 20 tpy flare cap along with the removal of the delay of repair provisions and the proposed PRD provisions may have unintended consequences leaving owners and operators with very few options for compliance if additional shutdowns and start-ups are needed to address a leaking component and/or if a PRD discharge to a flare occurs.
• the EPA's proposed solution to replace flares with thermal oxidizers is not practical from a timing or cost perspective.
• thermal oxidizers are generally not suitable destruction devices for PRD effluents; therefore, plants would need a new thermal oxidizer along with a flare operating for unplanned discharges like PRD vents, and the EPA's cost estimates are not reflective of the actual costs that would incur in the 2023-2026 timeframe to install a new thermal oxidizer system. It is common practice to size a thermal oxidizer for a normal range of VOC concentrations and normal flow and have an emergency flare to accommodate a higher concentration and flow from an event. Using a thermal oxidizer in lieu of a flare to manage EtO emissions would necessitate designing the oxidizer to accommodate these larger intermittent flows and higher inlet concentrations of VOC; however, such a design might not be feasible because normal operation might represent too much of a “turndown” from emergency operation.
• lead/delivery time for a new thermal oxidizer system could exceed 52 weeks, but 12 months is a best estimate.
• replacing flares with a thermal oxidizer essentially maintains greenhouse gas emissions at the same level since EtO is combusted in both applications.
• there may be safety and reliability considerations not addressed by the EPA with the use of a thermal oxidizer, which would require design and process safety features due to the reactive and flammable nature of EtO.

Commenters said that instead of replacing flares with thermal oxidizers to meet the EPA's proposed EtO flare load limit, owners and operators could potentially add a water scrubber between vent sources like storage vessels and railcar loading/unloading operations and the existing flares; however, this option would likely still need a larger EtO flare load limit than the 20 tpy limit the EPA has proposed. The commenters said that water from the scrubber could then be routed to the EtO manufacturing processes at these sites where the EtO could be recovered as a product stream. However, the commenters pointed out that during times when the EtO manufacturing process unit is not in service, the internal scrubber systems would need to be turned off as there is no viable location to recover the EtO out of the scrubber water stream. Thus, during times when storage vessels and railcar loading/unloading operations would need to occur but the production plant is not in service, the vent gas from the tank vents and loading/unloading operations would need to be routed to the existing logistics flares. In other words, the commenters contended that the amount of EtO that would be routed to these flares in the future is a function of the operating time of the production plant.

In summary, commenters said they are concerned that projects that would be needed in order to meet the 20 tpy EtO flare load limit could not be implemented within 2 years as proposed in 40 CFR 63.100(k)(11), nor would the EPA's proposed control option achieve the intended reductions and may actually result in an increase in secondary emissions. Thus, these commenters requested that the EPA either refrain from finalizing the proposed flare cap or increase the flare cap based on a 99 percent control efficiency and provide 3 years for facilities to comply with the revision.

Response: We are not finalizing the requirement at 40 CFR 63.108(p) that prohibits owners and operators from sending more than 20 tons of EtO to all of their flares combined in any consecutive 12-month period. In other words, we are not including an EtO flare load limit in the final rule. In response to a comment discussed in section 1.1 of the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking, we have determined that it is appropriate to use a different modeling approach for the final rule than the approach we used for the proposed rule ( i.e., we used the TCEQ modeling guidelines to calculate effective flare stack parameters for the final rule in lieu of modeling all flare releases as standard point sources with temperatures less than 1,000 Kelvin and velocities less than one meter per second for the proposed rule). As explained in that response, modeling flare emissions using effective stack parameters accounts for heat release of the flare and better characterizes plume rise. After applying this approach for the final rule, we have determined the EtO flare load limit is no longer necessary as flares controlling EtO are no longer significant contributors to risk. Using the reported EtO emissions of 2.87 tpy (post-control) from the highest-emitting facility, we estimate that the facility's current combined total EtO load to flares is about 143.5 tpy (pre-control). Based on the revised modeling, a flare controlling 143.5 tpy (far higher than the proposed 20 tpy flare cap) is not a significant risk driver. Using the TCEQ modeling guidelines for flares, we have determined that risk for the SOCMI source category remains below 100-in-1 million without the need of an EtO flare load limit, but only after implementation of the standards we are finalizing for: (1) Process vents, (2) storage vessels, (3) equipment leaks, (4) heat exchange systems, and (5) wastewater “in ethylene oxide service,” as well as implementation of the final requirements to reduce EtO emissions from maintenance vents and PRDs. We note that by not finalizing an EtO flare load limit we also obviate the inconsistency we unintentionally created in the proposed rule by requiring owners and operators to comply with an EtO flare load limit while also requiring owners and operators to minimize emissions from PRDs by routing them to flares instead of venting to the atmosphere.

vi. PRDs in EtO Service

Comment: Commenters argued that the requirement at 40 CFR 63.165(e)(3)(v)(D) that considers any atmospheric release from a PRD in EtO service a violation will not reduce risk given that PRD releases are non-routine events that take place to prevent catastrophic equipment failure. The commenters contended that deeming atmospheric PRD releases a violation will not reduce their occurrence. The commenters stated that the proposed work practice standards at 40 CFR 63.165(e) (including the deviation determination criteria at 40 CFR 63.165(e)(3)(v)(A) through (C)) already provide an effective framework for addressing PRD releases.

The commenters added it is not cost-effective to route all PRDs to control devices; and the EPA wrongly assumes that all releases from PRDs in EtO service can and will be controlled as process vents as a result of the prohibition on such releases. The commenters provided numerous examples of why certain PRDs cannot be safely routed to a control device and/or would be technically infeasible in many process designs such as hydraulic limitations of flare systems or other controls, PRD backpressure, EtO incompatibility with other collected compounds, and polymerization of ethylene in closed vent systems. Commenters argued that because PRD releases are usually non-routine, infrequent, and episodic, piping and the control device would have to be sized to accommodate significantly larger flow than normal process vents, and the control device would be required to operate in an indefinite “stand-by” mode to accommodate unexpected and emergency releases. A commenter said “stand-by” mode may also require significant amounts of fuel and generate secondary combustion emissions on a continuous basis for a release that may or may not occur.

Response: We are finalizing these requirements for PRDs in EtO service pursuant to CAA section 112(f)(2), on the basis of risks being unacceptable. Where we find risks are unacceptable, the EPA must determine the emissions standards necessary to reduce risk to an acceptable level. Because emissions of EtO from the SOCMI source category result in unacceptable risks, we proposed and are finalizing requirements that would reduce risks to an acceptable level, including provisions that would make all PRD releases of EtO directly to the atmosphere a violation of the standard. As explained in response to a comment in section 1.1 of the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking, the EPA modeled certain PRD releases of EtO during maintenance events which resulted in very high risk from one facility ( i.e., EtO risk from process vent emission sources emitted through PRDs is approximately 75 percent of the Port Neches facility's total SOCMI source category risk of 2000-in-1 million). There is no reason for not considering the impact of these events in our risk modeling and rulemaking. In response, we proposed and are finalizing a requirement that releases from PRDs in EtO service are a violation of the emission standard.

vii. Other EtO Related Requirements

Comment: Commenters asserted that the EPA acted unreasonably in imposing controls across the entire “HON source category.” The commenters contended that the EPA may require those facilities that pose unacceptable risk to implement targeted additional controls, but it is arbitrary and capricious to attempt to impose those same requirements everywhere despite the absence of risk. A commenter provided an example where under the proposed rule, both Huntsman Conroe and Huntsman Geismar facilities would be heavily burdened by the proposed HON EtO control requirements even though the EPA found that neither facility poses unacceptable risk.

These commenters said that the EPA's proposed response to 8 facilities with EtO risk above the presumptive limit is a one-size-fits-all approach to addressing risk from the source category that unreasonably imposes stringent control requirements across all emissions sources at every facility, rather than addressing the residual risks that were actually identified. The commenters said the approach is inconsistent with CAA section 112(f) because half of the facilities affected by the proposed EtO standards do not present unacceptable risk to surrounding areas, yet the EPA proposes to impose emissions standards on these facilities that were derived without consideration of cost. A commenter pointed out that Congress explicitly granted the EPA the authority to consider variations among sources in promulgating emission standards under CAA section 112 through subcategorization; yet, the EPA has failed to utilize this statutorily available tool here. Commenters said that even if the Agency chooses not to subcategorize, the EPA has recognized that it is unreasonable to require controls on all facilities when a more targeted and less costly option may achieve an acceptable level of risk. The commenters pointed out that the EPA used a tailored approach in the RTR for sterilization facilities (see 88 FR 22790, 22826-28) and the proposed MON rule (see 84 FR 69182) which applied different levels of stringency in accordance with the different facilities' MIRs (in other words, the EPA tailored its acceptability analysis to address risk from the highest risk sources).

A commenter added that the EPA's approach is not sufficiently targeted because the applicability of the new EtO emissions standards would be governed by the definition of “in ethylene oxide service” that the EPA adopted in the MON, which was not derived with any consideration of the emissions characteristics of the SOCMI source category or the risk profile determined by the EPA's risk assessment of the SOCMI source category. The commenter contended that adopting the MON definition of “in ethylene oxide service” results in new EtO emissions standards that apply to approximately twice as many affected facilities as needed to address the risk that the EPA determines to be actionable.

Response: We disagree with the commenters that the EPA acted unreasonably in imposing controls across the entire SOCMI source category (note the commenter used the phrase “HON source category;” however, the source category covered by the HON is actually the SOCMI source category). We also disagree with the commenters that our action to impose the same EtO requirements on each owner and operator is arbitrary and capricious.

As stated in the preamble to the proposed rule (see 88 FR 25080, April 25, 2023), we identified EtO as the cancer risk driver from HON sources; and we are aware of 15 HON facilities reporting more than 0.1 tpy of EtO emissions in their emissions inventories from HON processes and two other facilities that are new or under construction with HON processes that we expect will exceed this threshold (but for which we do not yet have emissions inventory information). Of these 17 facilities, 12 facilities produce and emit EtO, which is a process subject to the HON MACT standards. In addition, all 17 of these facilities have additional HON processes that use and emit EtO in the production of glycols, glycol ethers, or ethanolamines. Therefore, we are not imposing EtO controls across the entire SOCMI source category. Rather, in order to reduce emissions of EtO from HON processes, the EPA is finalizing more stringent control requirements for process vents, storage vessels, equipment leaks, heat exchange systems, wastewater, maintenance vents, and PRDs that emit or have the potential to emit EtO. While it is true from our residual risk assessment that eight of the 17 facilities with emissions of EtO from various HON processes have cancer risks above 100-in-1 million, the standards are national standards that apply to specific types of sources rather than specific facilities, and the revisions ensure that risks from the source category are acceptable and that the standards provide an ample margin of safety to protect public health. As such, we disagree with the commenter that we should target additional controls on only facilities that pose unacceptable risk.

For these same reasons, we also disagree with the commenter that adopting the MON definition of “in ethylene oxide service” results in new EtO emissions standards that apply to approximately twice as many affected facilities as needed to address the risk that the EPA determines to be actionable. Although, as noted in our proposal, similar emission sources and standards exist between the HON and MON, we disagree with the commenter that we did not give any consideration of the emissions characteristics of the SOCMI source category or the risk profile determined by the EPA's risk assessment of the SOCMI source category. The scientific and technical bases for the EPA's proposed action are voluminously presented in the numerous supporting memoranda contained in the public docket for the proposed rulemaking. See, e.g., the documents titled Residual Risk Assessment for the SOCMI Source Category in Support of the 2023 Risk and Technology Review Proposed Rule; Analysis of Control Options for Process Vents and Storage Vessels to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Equipment Leaks to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Heat Exchange Systems to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; Analysis of Control Options for Wastewater Streams to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for Processes Subject to HON; (see Docket Item No. EPA-HQ-OAR-2022-0730-0085, -0074, -0003, -0071, and -0087, respectively).

e. P&R I NESHAP Rule Changes Related to Chloroprene

i. Process Vents and Storage Vessels in Chloroprene Service

Comment: A commenter argued that the EPA's proposal at 40 CFR 63.484(u), 40 CFR 63.485(y), and 40 CFR 63.487(j) to require a control device that reduces chloroprene by greater than or equal to 99.9 percent by weight is unreasonable in light of the EPA's involvement in the decision to install a regenerative thermal oxidizer (RTO) at one facility with a chloroprene destruction efficiency of 98 percent and the “monomer emission reduction project” (MERP) system with a chloroprene destruction efficiency of 99.3 percent. The commenter made the following points regarding these installations:

During the first six months of 2016, the facility engaged in numerous meetings with both the EPA and the LDEQ to discuss options for reducing chloroprene emissions, including different types of control devices. Records of these discussions show that, in October 2016, the facility presented slides to the EPA and the LDEQ that summarized control device options, including a direct-fired thermal oxidizer (the only option that could achieve a chloroprene destruction efficiency of 99.9 percent) and an RTO, which was expected to have a chloroprene destruction efficiency of 98 percent. As the slide indicated, however, the cost of operating a direct-fired thermal oxidizer would be very high because it would burn enormous amounts of natural gas. This is why in June 2016, the facility proposed to install an RTO, which would have similar up-front capital costs but would have much lower operating costs (and much lower CO₂ emissions) because it would require much less natural gas to operate.

In December 2016, the LDEQ held a large public meeting at its headquarters, with the EPA and the Department of Justice in attendance. Before this meeting, an EPA researcher advised EPA officials that, to achieve a risk-level of 1-in-10,000, ambient concentrations of chloroprene in the community could be no higher than 0.2 ug/m³ . His memorandum making this assertion was also released publicly. At this meeting, the facility presented results of an air dispersion modeling study, which showed then-existing (2016) ambient concentrations and the concentrations that would be expected if the facility implemented the emission reduction projects it had proposed, including the installation of an RTO with a chloroprene destruction efficiency of 98 percent. The modeling results presented to the EPA, the LDEQ, and the public showed that offsite concentrations would be significantly reduced but would still be higher than 0.2 ug/m³ .

Following the public hearing, the facility, the EPA, and the LDEQ finalized the terms of a voluntary Administrative Order on Consent, which the facility and the LDEQ signed on January 6, 2017. The EPA and lawyers from the Department of Justice were present for all significant discussions, and the EPA was heavily involved in the Administrative Order on Consent's development, providing numerous comments and making a number of demands reflected in the order. Under the Administrative Order on Consent, the facility agreed to “install and operate . . . a Regenerative Thermal Oxidizer (RTO)” capable of “achiev[ing] at least a 98 percent [destruction or removal efficiency].” The facility also agreed to install the MERP and to achieve an 85 percent reduction in total chloroprene emissions from the facility, principally from the “Chloroprene” Unit, to the facility's halogen acid production furnace.

The commenter claimed that these projects reduced facility chloroprene emissions by 85 percent at a capital cost of $35 million, plus a significant increase in annual operating costs; and of the $35 million, the MERP cost approximately $9 million. The commenter requested that the EPA take this history into account as it develops the final rule given that it is unreasonable to ignore the investments that the facility recently made to reduce chloroprene emissions when they were made under the oversight of the LDEQ and the EPA, and with the EPA's full knowledge of the 2010 IRIS inhalation URE value for chloroprene. The commenter contended that the very small emission reductions that would be achieved by increasing the chloroprene destruction efficiency to 99.9 percent are enormously expensive, more than $21 million per ton annually. The commenter said the current chloroprene emissions from the existing RTO are approximately 0.84 tpy; therefore, if all the emission streams currently routed to the existing RTO were instead routed to a new direct-fired thermal oxidizer with a chloroprene destruction efficiency to 99.9 percent, chloroprene emissions would be reduced from 0.84 tpy to 0.04 tpy (an annual reduction of 0.79 tons). The commenter claimed that the annualized cost of achieving this is almost $3.7 million, and the cost-per-ton of chloroprene emission reduction would be more than $4.6 million. The commenter submitted a similar analysis for their MERP system and claimed that if all the vent streams currently controlled by the MERP were instead routed to a control device with a chloroprene destruction efficiency of 99.9 percent (testing has demonstrated that the MERP achieves a destruction or removal efficiency of 99.3 percent on an overall basis), the reduction in annual chloroprene emissions would be 50-60 pounds, depending on production.

The commenter said that they hired consultants to evaluate multiple options for control device configuration that would achieve a chloroprene destruction efficiency of 99.9 percent as required by the proposed rule. The commenter said that modifying their existing RTO to achieve a chloroprene destruction efficiency of 99.9 percent is not possible given that high levels of chlorine in their exhaust streams would poison the catalyst. The commenter added that even if their existing RTO could achieve a chloroprene destruction efficiency of 99.9 percent, it does not have capacity to accommodate the additional streams that would have to be routed to it under the proposed rule; thus, the proposed rule would require the installation of one or more new control devices that could accommodate very high air flows containing very low concentrations of VOC, including chloroprene. The commenter provided specific details of other control options and acknowledged that the destruction efficiency of an RTO can be increased to 99.9 percent by adding an additional oxidation step (which involves the installation of a polishing catalyst bed in the stack that reheats the treated gas); however, the commenter asserted that all other options that they evaluated ( e.g., installing new RTOs and/or direct fired thermal oxidizers) would require enormous amounts of fuel consumption, quench water, and power consumption only to achieve minimum reductions.

The commenter asserted that the EPA's cost estimate to install a new direct fired thermal oxidizer is “far from realistic” given that their consultant estimated the equipment purchase costs for a new direct fired thermal oxidizer with recuperative heat exchange capabilities would be approximately $12 million and total annual costs of $39 million. The commenter said the EPA assumed a slightly smaller direct fired thermal oxidizer than what they believe would be necessary and the EPA estimated an equipment purchase cost of $5 million and total annual costs of $10.1 million; however, the commenter asserted that it is not clear if the EPA's estimate includes the additional scrubber capacity or the high nickel alloy materials that would be needed for certain components. The commenter added that the EPA has not estimated the costs that would be required to upgrade the electrical and natural gas infrastructure, or expand the wastewater treatment plant (WWTP), which are all actions that would be necessary to install a new direct fired thermal oxidizer.

In summary, the commenter claimed that given that it is not possible to modify their existing RTO and MERP to achieve a chloroprene destruction efficiency of 99.9 percent, the proposed rule would leave the facility with $35 million of stranded investment which was made fewer than 6 years ago to reduce chloroprene emissions in consultation with the EPA. The commenter said that even though the option of installing a direct-fired thermal oxidizer was discussed in 2016, at no point did the EPA suggest that an RTO would not be sufficient or that a direct-fired thermal oxidizer might be required. The commenter asserted that there has been no change since 2016 in either (1) the EPA's views about the risk of chloroprene exposure or (2) its understanding of the offsite concentrations that would be achieved under the Administrative Order on Consent.

Response: We reevaluated whether we could change the proposed 99.9 percent by weight reduction standard to 98 percent by weight given the commenter's arguments that their existing RTO and MERP cannot achieve a chloroprene reduction of 99.9 percent by weight. In our reevaluation for the final rule, we determined that revising the performance standard for process vents and storage vessels in chloroprene service (from a 99.9 percent by weight reduction requirement as proposed to a 98 percent by weight reduction requirement in the final rule) will still maintain the MIR at 100-in-1 million for the Neoprene Production source category and thereby result in the source category chloroprene emissions being reduced to acceptable levels. We have made this change in the final rule at 40 CFR 63.484(u)(1), 40 CFR 63.485(y)(1), 40 CFR 63.487(j)(1), and 40 CFR 63.510(a)(2). While considering the current chloroprene emissions from both the existing RTO (0.84 tpy) and MERP (0.02 tpy based on our review of the emissions inventory calculations), we have determined the revised performance requirements for the final rule will still reduce risk from Neoprene Production source category emissions to an acceptable level and also provide an ample margin of safety to protect public health (as was proposed) for the Neoprene Production source category. We also have determined that no additional requirements are needed to prevent an adverse environmental effect (as was proposed). In light of this, we believe the commenter's existing RTO and MERP can be used to meet the revised requirements for the final rule and would no longer be considered a stranded investment as the commenter has claimed.

Comment: A commenter said they support the EPA's proposed rule text at 40 CFR 63.485(y) that requires owners and operators to reduce emissions of chloroprene from continuous front-end process vents in chloroprene service at affected sources producing neoprene by venting emissions through a closed-vent system to a non-flare control device that reduces chloroprene by greater than or equal to 99.9 percent by weight, to a concentration less than 1 ppmv for each process vent, or to less than 5 lb/yr for all combined process vents. The commenter said they also support the EPA's proposed rule text at 40 CFR 63.487(j) to add these same chloroprene standards for batch front-end process vents at affected sources producing neoprene. However, another commenter argued that the EPA's oversimplification of the design configurations necessary to comply with these proposed performance standards (which the EPA presented in Docket Item No. EPA-HQ-OAR-2022-0730-0083) results in cost estimates that are much too low. The commenter asserted the EPA did not consider in their analysis the following technical and process safety challenges:

• The EPA assumed that all the sources at this commenter's facility are to be enclosed and routed to a new direct fired thermal oxidizer are in close proximity to each other, but the wash belts are actually located in the Finishing building, which is separate from the Poly building.
• The EPA did not account for complicated duct and piping (e.g., unique pipe lengths, diameters, number of bends), which also impacts pump specifications and other equipment such as the blower.
• The existing thermal oxidizer cannot accommodate the additional vent streams from the wash belts (at current flow rates). Each wash belt vent hood operates at approximately 28,000 standard cubic feet per minute (scfm), and total chloroprene emissions for both wash belt vents combined is approximately 3.3 tpy (2022 reported value).
• Installing an enclosure around the wash belts creates safety concerns given that the wash belt blower motors are equipped with variable frequency drives which can change air flow through the vent hoods; the potential variability in air flows would need to be evaluated by an industrial hygienist to ensure compliance with personnel exposure requirements, or to make recommendations for additional protective equipment.
• Wash belts require frequent, manual intervention from area personnel to ensure stable operation; workers must have physical access to the wash belt area to perform routine maintenance and repairs.
• Wash belt enclosures would need to be transparent to allow visual inspection of the process without entry and would also need to be durable enough to withstand frequent disassembly and reassembly.
• Any changes in airflows or pressures, such as those that will occur when installing enclosures and adjusting blower speeds (for the wash belts), will need to be evaluated to ensure that product quality standards are achievable and to ensure that production rates are not negatively impacted. The finishing process is designed to supply very precise air flows and pressure differentials throughout in order to maintain adhesion of the web (Neoprene product film) to the girt (flexible sheeting that guides the web through the process).

The commenter submitted a cost estimate of $3.6 million for the purchase of a direct fired thermal oxidizer with a chloroprene destruction efficiency of 99.9 percent that would be sized to accommodate waste gas from the wash belts. The commenter estimated the total cost for installing and operating the thermal oxidizer would be about $18 million. The commenter asserted that because of the low VOC content in the exhaust stream, natural gas consumption would be high, and the total annualized costs would be almost $3.0 million (not including the capital costs for the enclosure and associated infrastructure). The commenter stated that the cost-per-ton of chloroprene emission reduction would be approximately $0.9 million (based on the 3.3 tpy of chloroprene emissions reported in their 2022 inventory). The commenter added that operating the new thermal oxidizer would contribute to environmental harm including 16,200 metric tons a year of carbon dioxide equivalents (CO₂ e).

Response: We acknowledge commenters' support and opposition for the provision at 40 CFR 63.485(y) that requires owners and operators to reduce emissions of chloroprene from continuous front-end process vents in chloroprene service at affected sources producing neoprene by venting emissions through a closed-vent system to a non-flare control device that reduces chloroprene by greater than or equal to 99 percent by weight, to a concentration less than 1 ppmv for each process vent, or to less than 5 lb/yr for all combined process vents. We also acknowledge commenters' support and opposition for the provision at 40 CFR 63.487(j) to add these same chloroprene standards for batch front-end process vents at affected sources producing neoprene.

As discussed in the preamble to the proposed rule (see 88 FR 25080, April 25, 2023), we had determined that the only viable way to meet these proposed standards is to enclose all of the polymer batch reactors, emulsion storage vessels, strainers, and wash belt dryers and route the vapors to a thermal oxidizer (and thereby reduce chloroprene emissions from these sources, which are fugitive in nature); and the result of this control option would reduce chloroprene emissions from the polymer building, unstripped resin emulsion storage vessels, and wash belt dryers by 11.3 tpy (from 12 tpy to 0.7 tpy). Although we continue to stand by our analysis that chloroprene emissions from these emission sources must be reduced to decrease risk posed by emissions from neoprene production processes to an acceptable level, we reevaluated whether we could change the 99.9 percent by weight reduction standard to 98 percent by weight given a commenter's arguments (as discussed in section 3.1 of the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking) that their existing thermal oxidizer cannot achieve a chloroprene reduction of 99.9 percent by weight. In our reevaluation for the final rule, we determined that revising the performance standard for process vents and storage vessels in chloroprene service (from a 99.9 percent by weight reduction requirement as proposed to a 98 percent by weight reduction requirement in the final rule) will still maintain the MIR at 100-in-1 million for the Neoprene Production source category. The result of this revision in the final rule will reduce chloroprene emissions from the polymer building, unstripped resin emulsion storage vessels, and the wash belt dryers from 12 tpy to 0.9 tpy ( i.e., a reduction of 11.1 tpy chloroprene in lieu of 11.3 tpy as proposed). We have determined these revised performance requirements for the final rule will still reduce risk to an acceptable level and also provide an ample margin of safety to protect public health (as was proposed) from P&R I emission sources. We also have determined that no additional requirements are needed to prevent an adverse environmental effect (as was proposed).

We also acknowledge that the wash belt dryers are located in the finishing building, which is separate from the polymer building; and at proposal, we incorrectly assumed these process vents were front-end process vents when in actuality they are considered back-end process vents according to NESHAP subpart U. As such, we are clarifying in the final rule that the requirements we are finalizing for controlling chloroprene from process vents in the Neoprene Production source category, not only applies to continuous front-end process vents in chloroprene service and batch front-end process vents in chloroprene service, but also back-end process vents in chloroprene service. In other words, we are finalizing at 40 CFR 63.494(a)(7) a requirement that owners and operators reduce emissions of chloroprene from back-end process vents in chloroprene service at affected sources producing neoprene by venting emissions through a closed-vent system to a non-flare control device that reduces chloroprene by greater than or equal to 98 percent by weight, to a concentration less than 1 ppmv for each process vent, or to less than 5 lb/yr for all combined process vents. We anticipate that the facility will still need to install an additional thermal oxidizer in order to comply with the final performance standard for process vents and storage vessels in chloroprene service. We also note that while the commenter claims that the 3.3 tpy chloroprene emissions from the wash belt dryers were reported in their 2022 inventory, we stand by our decision to use the facility's 2019 emissions inventory which shows 3.9 tpy chloroprene emissions from the wash belt dryers. As previously mentioned, the facility's emissions inventory was provided to the EPA pursuant to our CAA section 114 request. In particular, the EPA requested emission inventories from the past 5 years ( i.e., 2016-2020) from the facility's operations as part of this request. As 2017 NEI data did not represent current controls being employed at Denka Performance Elastomers, LLC, the EPA chose to use the most current data it had available and that is reflective of current operations and emissions. Given concerns about decreased production and emissions in 2020 from the COVID-19 pandemic, the EPA elected to use Denka Performance Elastomer, LLC's 2019 emissions inventory submitted as part of the CAA section 114 request in its risk assessment for the SOCMI and Neoprene Production source categories in lieu of the 2017 NEI data. Even if we were to revise emissions based on the facility's 2022 emissions inventory, we continue to believe our cost estimate to install permanent total enclosures, a thermal oxidizer, and ductwork and associated support equipment (using the procedures in the EPA's 2002 Control Cost Manual) is reasonable, and note that cost does not play a role in setting standards that are necessary to reduce risk to an acceptable level under step one of the Benzene NESHAP approach codified in CAA section 112(f). Furthermore, with regard to a commenter's specific objections to installing a permanent total enclosure around their wash belts/dryers, we note that even though we costed out permanent total enclosures for these emission sources in our proposal, there is no explicit requirement in the proposed rule, or final rule, to install permanent total enclosures around these emission sources. We opted for this option as the most conservative way to collect the fugitive chloroprene emissions from the wash belts/dryers and route them to a control device such as a thermal oxidizer. Nothing in the proposed rule, or final rule, prevents the facility from doing something different than installing a permanent total enclosure around their wash belts/dryers so long as the owner or operator can achieve the emission standard we are finalizing at 40 CFR 63.494(a)(7) for back-end process vents ( i.e., the requirement that owners and operators reduce emissions of chloroprene from back-end process vents in chloroprene service at affected sources producing neoprene by venting emissions through a closed-vent system to a non-flare control device that reduces chloroprene by greater than or equal to 98 percent by weight, to a concentration less than 1 ppmv for each process vent, or to less than 5 lb/yr for all combined process vents).

Even so, we anticipate cost to be less of a concern for the final rule given that the facility should be able to use their existing thermal oxidizer to meet the revised performance standard (reduce chloroprene by greater than or equal to 98 percent by weight) for at least some of their process vents and storage vessels in chloroprene service.

ii. Wastewater in Chloroprene Service

Comment: A commenter said that they support the proposed provision at 40 CFR 63.501(a)(10)(iv) to revise the Group 1 wastewater stream threshold to include wastewater streams in chloroprene service ( i.e., wastewater streams with total annual average concentration of chloroprene greater than or equal to 10 ppmw at any flow rate). However, another commenter said the EPA's analysis of the costs and emission reductions associated with reducing chloroprene emissions from wastewater streams at neoprene production processes (see Docket Item No. EPA-HQ-OAR-2022-0730-0092) has several major flaws. The commenter said the EPA's analysis suggests that the proposed control requirements for wastewater would reduce chloroprene emissions by 17.7 tpy, when in fact the emission reductions would be closer to 1 tpy; therefore, the EPA's analysis substantially overstates the emission reductions that would be achieved, and the efficacy and cost-effectiveness of the proposed requirements at 40 CFR 63.501(a)(10)(iv). The commenter provided the following critiques of the EPA's analysis:

• there are approximately 13.5 tpy of wastewater in chloroprene service that pass through the WWTP, not 26.3, which the EPA incorrectly used in their analysis.
• although the EPA acknowledges that some controls may already be in place, their analysis goes on to analyze the effectiveness of the proposed requirements based on the assumption that there are no such controls; however, the facility already employs an air stripping system to treat the decanter and kettle line wastewater streams. The air stripping occurs in the air sparging tank, which is routed to the onsite RTO. Testing suggests that the air sparging tank achieves a control efficiency of approximately 95 percent. Thus, of the 7.5 tpy of chloroprene contained in these 2 streams, all but ~0.4 tpy are removed via air stripping and directed to RTO. This amount, ~0.4 tpy, then goes to the WWTP, which includes a biological treatment system that reduces it by approximately 80 percent, meaning that chloroprene emissions from the decanter and kettle line streams are likely less than 0.1 tpy. Thus, accounting for the control efficiency of the air sparging tank and the biologic treatment system, almost 99 percent of the 7.5 tpy contained in the decanter and kettle line wastewater streams is already controlled. Even if steam stripping achieves a 99 percent capture efficiency in these streams, it would only reduce emissions by about 0.025 tpy (to 0.075 tpy as compared to 0.1 tpy today).
• based on limited testing of the air stripper rundown streams, they contain approximately 6.0 tpy of chloroprene. These streams are routed to the outdoor brine pit, which then discharges to the WWTP. The EPA did not consider that the WWTP includes biological control that currently reduces chloroprene emissions by approximately 80 percent. It is true that some emissions to air occur as the wastewater is conveyed through the outdoor brine pit and to the WWTP, but it is incorrect for the EPA to consider it “uncontrolled.” Assuming the Fe of 68 percent suggested by the EPA, the maximum fraction of the mass of chloroprene that could end up as an air emission is about 4 tpy before biological control. Applying the 80 percent estimated biological control removal rate, current emissions are approximately 0.8 tpy from the air stripper rundown streams. Even if the EPA's assumption of a 99 percent removal efficiency for steam stripping is accurate, it would reduce emissions by about 0.8 tpy from the stripper rundown streams.

The commenter concluded that when adding the 0.8 tpy from the stripper rundown streams to the 0.1 tpy reduction from the decanter and kettle line wastewater streams, the EPA's proposed steam stripping requirement is likely to reduce current chloroprene emissions by about 1 tpy (not by 17.7 tpy as the EPA had determined). The commenter added that there is also uncertainty as to whether steam stripping would actually achieve 99 percent removal of the low concentrations of chloroprene in wastewater given that chloroprene is a halogenated alkane, and no information has been presented that is specific to steam stripping of chloroprene from wastewater at the concentrations present in wastewater at the facility. The commenter deduced that when using their expected actual emissions reductions of about 1 tpy, the cost effectiveness would be closer to $7.5 million per ton removed (without considering the cost of installing and operating a thermal oxidizer that would be required under the EPA's proposal to handle the chloroprene from the steam stripper unit), and not $426,900 per ton as the EPA has estimated.

Response: The EPA acknowledges the commenters' support for and opposition of the proposed wastewater provisions at 40 CFR 63.501(a)(10)(iv). We are finalizing these provisions as proposed. We disagree with the commenter's assertion that 13.5 tpy of wastewater in chloroprene service pass through the WWTP. We also disagree that our emissions reductions were overestimated. We believe 26.3 tpy of wastewater in chloroprene service pass through the WWTP ( i.e., the amount of chloroprene entering the air sparging tank) based on our review of emissions inventory calculations for wastewater entering the WWTP. We maintain that 17.7 tpy of emissions reductions is appropriate, based on a mass balance of the information provided in the emissions inventory calculations. The results of our mass balance suggest that our initial analysis is appropriate.

We also disagree with the commenter and maintain it was appropriate to assume no controls during our initial analysis such that a steam stripper would be placed before the air sparging tank. Simply put, the P&R I NESHAP (which references the HON wastewater requirements) requires all wastewater collection system components (tanks, surface impoundments, containers, individual drain systems, and oil-water separators) to be covered and upstream of the wastewater treatment process. However, the facility's wastewater treatment system is configured with an air sparging tank (air stripper), followed by an outdoor brine pit (open to the atmosphere), followed by biological treatment. Furthermore, the commenter claims their air stripper achieves approximately 95 percent control, but did not provide any data to corroborate this control efficiency. When taking the configuration of the facility's wastewater treatment system into account, we assumed no controls, since wastewater streams flow through a control device with an unknown control efficiency directly into an open brine pit.

Also, contrary to the commenter's remark regarding steam stripper performance, we believe the use of 99 percent removal of chloroprene from steam stripping is appropriate based on its Fr value. In the document titled Analysis of Control Options for Wastewater Streams to Reduce Residual Risk of Chloroprene from Neoprene Production Processes Subject to P&R I (see Docket Item No. EPA-HQ-OAR-2022-0730-0092), we explain that the EPA calculated the Fr values for a variety of HAP during the original rulemaking of the HON. The Fr is the fraction of a HAP that is stripped from wastewater and is an indicator of the extent to which a HAP is effectively removed during the steam stripping process. For chloroprene, the Fr has always been 99 percent in Table 9 to NESHAP subpart G and we maintain this is reflective of the current technology.

Finally, we remind the commenter that, due to the risk associated with chloroprene, cost does not play a role in setting standards that are necessary to reduce risk to an acceptable level under step one of the Benzene NESHAP approach codified in CAA section 112(f). Regardless of whether or not emissions reductions were underestimated (which we disagree with), a higher cost-effectiveness is not grounds for reevaluating the proposed provisions at 40 CFR 63.501(a)(10)(iv).

iii. Chloroprene Facility-Wide Cap

Comment: A commenter said they support the EPA's proposed rule text at 40 CFR 63.483(a)(10) that requires owners and operators to comply with a facility-wide chloroprene emissions cap of 3.8 tpy in any consecutive 12-month period for all neoprene production emission sources. However, another commenter argued that it is impossible to know whether the chloroprene emissions cap of 3.8 tpy is simply a “backstop” or an additional requirement that goes beyond the proposed requirements to control emissions of chloroprene from maintenance vents and PRDs, and process vents, storage vessels, and wastewater “in chloroprene service.” The commenter asserted that the EPA does not appear to have determined whether full compliance with the proposed requirements to control chloroprene from maintenance vents and PRDs, and process vents, storage vessels, and wastewater “in chloroprene service” would reduce the facility-wide emissions below the proposed chloroprene emissions cap of 3.8 tpy. The commenter also asserted that the EPA has not estimated the costs of reducing facility-wide emissions below this cap, nor does the EPA provide any details about the type of monitoring that would be required to demonstrate compliance with it. The commenter argued that given the EPA's determination that the chloroprene emissions cap of 3.8 tpy would protect public health with an ample margin of safety, the proposed requirements to control chloroprene from maintenance vents and PRDs, and process vents, storage vessels, and wastewater “in chloroprene service” are unlawful if they would force the facility to reduce emissions appreciably below 3.8 tpy. The commenter said that the EPA does not have authority to require emission reductions that go beyond what is necessary to protect public health with an ample margin of safety, unless they are based on cost-effective improvements in control technology under CAA section 112(d)(6).

Another commenter provided several reasons why the chloroprene emissions cap of 3.8 tpy is inappropriate, including: (1) The EPA back-calculated this cap from a flawed risk assessment; (2) the cap is unverifiable and therefore not enforceable, particularly here where it encompasses not only non-flare point sources (which can, with some effort, be properly monitored) but also flare and numerous fugitive sources (whose emissions simply cannot be tested, monitored, and verified); and (3) there have recently been large problems with “unknown” and therefore unreported emissions at the facility ( e.g., in 2022, the EPA discovered that the facility was using an unpermitted brine pit to allow poly-kettle waste to off-gas chloroprene).

Response: We are not finalizing the proposed requirement at 40 CFR 63.483(a)(10) that would have required owners and operators to comply with a chloroprene emissions cap of 3.8 tpy in any consecutive 12-month period for all neoprene production emission sources. The proposed facility-wide chloroprene emissions cap was intended to address unknown or uncertain emission sources in the Neoprene Production source category, including emissions from back-end process operations. However, we agree with a commenter that the proposed facility-wide chloroprene emissions cap is confusing on how it would be applied beyond the proposed requirements for emission sources in chloroprene service. Instead, we believe the fenceline monitoring requirements that we are finalizing will serve as a reasonable backstop for limiting emissions and addressing fugitive and any unknown emission sources in the Neoprene Production source category as well as whole-facility chloroprene emissions. We are also clarifying in the final rule that the requirements we proposed for controlling chloroprene from process vents in the Neoprene Production source category apply not only to continuous front-end process vents in chloroprene service and batch front-end process vents in chloroprene service, but also to back-end process vents in chloroprene service. For more details about this, see our responses to comments in section IV.A.3.e.i of this preamble.

iv. Other Chloroprene Related Requirements

Comment: A commenter said they supported the EPA's proposed rule text at 40 CFR 63.509 sampling and analysis procedures for owners and operators of affected sources producing neoprene to demonstrate that process equipment does, or does not, meet the proposed definition of being “in chloroprene service.”

Response: The EPA acknowledges the commenter's support of the sampling and analysis procedures used to determine whether process equipment is “in chloroprene service.” We are making the following minor changes in the final rule to clarify our intent: (1) For process vents, we have clarified within the definition of “in chloroprene service” that the 5 lb/yr chloroprene mass threshold for combined process vents be on a EPPU-by-EPPU basis; (2) For storage vessels, we are revising the phrasing of “sampling and analysis is performed as specified in § 63.509” within the definition of “in chloroprene service” to “the procedures specified in § 63.509 are performed”; and (3) we have clarified at 40 CFR 63.509(a) that the sampling site shall be after the last recovery device (if any recovery devices are present) but prior to the inlet of any control device that is present and prior to release to the atmosphere.

Comment: A commenter (0172) requested that the EPA recognize in the final rule that OGI is effective for detecting chloroprene leaks and work with their facility to develop a protocol for LDAR that could be included as a compliance option. The commenter claimed that the LDAR requirement in the proposed rule would require them to hire additional technicians (likely 3 additional workers) and purchase additional equipment. The commenter said that they spoke to leak detection experts at Montrose Environmental who said that a forward looking infrared cooled G304 camera would likely be an effective tool for monitoring and detecting chloroprene leaks. The commenter stated that they completed a one-day field test with such a camera and found that it was effective for detecting chloroprene leaks.

Response: We did not propose control options for equipment leaks to reduce chloroprene risk from the Neoprene Production source category. To reduce risk from the Neoprene Production source category to an acceptable level, we proposed to require control of chloroprene for: (1) Process vents, (2) storage vessels, and (3) wastewater “in chloroprene service.” We also proposed requirements to reduce chloroprene emissions from maintenance vents and PRDs. See section III.B.2.b of the preamble to the proposed rule for more details (88 FR 25080, April 25, 2023). However, we did make an error in the document titled Proposed Regulation Edits for 40 CFR part 63 Subpart U: National Emission Standards for Hazardous Air Pollutant Emissions: Group I Polymers and Resins (see Docket Item No. EPA-HQ-OAR-2022-0730-0066) that suggests at 40 CFR 63.502(a)(6) we were proposing to regulate certain equipment in chloroprene service.

The EPA has not provided an OGI-only option for detection for chloroprene leaks. Although the commenter mentions a one-day study performed by Montrose Environmental on the effectiveness of a particular OGI camera's ability to see chloroprene emissions, no information from that study was submitted. Additionally, no information on the detection level determined during the study or the environmental conditions of the study were submitted. Because the detection capabilities of OGI cameras are highly influenced by environmental conditions, this is important data to understand, and it is unlikely that a one-day study would provide information on the capabilities of the camera in the range of environmental conditions under which field surveys would normally be conducted.

Although the EPA recently finalized a protocol for using OGI in the detection of VOC and methane leaks (40 CFR part 60 appendix K), we note that the protocol is geared towards midwave OGI cameras that operate with a filter in a particular spectral range (around 3.3 microns) where methane and many VOC compounds have a spectral peak. The type of OGI camera the protocol is geared towards is not suited to finding leaks of chloroprene because chloroprene does not have a strong peak in the spectral range of these cameras, which means that only very high leaks of chloroprene would be visible to these cameras. The OGI camera mentioned by the commenter has a filter in a different spectral range. The EPA has not studied this camera to understand its detection capabilities, especially in regard to chloroprene, which is a risk driver for the source category, nor could the EPA readily find information on the ability of this OGI camera to see leaks of chloroprene. Because the leak definitions for the source category are low, on the order of 500 to 1000 ppm for most equipment, it is extremely important to understand the detection capability of an OGI camera being used at these sources, especially considering that while the OGI cameras the EPA has studied are effective at finding large leaks for many compounds, OGI cameras tend to be less effective at finding low-level leaks.

Even so, P&R I facilities currently have an option to use OGI through an alternative work practice to detect leaks from equipment at 40 CFR 63.11(c), (d), and (e). This alternative work practice includes provisions for using OGI in combination with annual monitoring using EPA Method 21 (and not as an alternative). The alternative work practice is not geared towards a particular type of OGI camera, and instead, requires owners and operators to perform daily instrument checks based on the detection levels and concentration of detectable chemicals in the equipment being surveyed.

4. What is the rationale for our final approach and final decisions for the risk review?

As noted in our proposal, the EPA sets standards under CAA section 112(f)(2) using “a two-step standard-setting approach, with an analytical first step to determine an `acceptable risk' that considers all health information, including risk estimation uncertainty, and includes a presumptive benchmark on maximum individual lifetime risk (MIR) of approximately 1-in-10 thousand” (88 FR 25080, April 25, 2023; see also 54 FR 38045, September 9, 1989.) We weigh all health risk factors in our risk acceptability determination, including the cancer MIR, cancer incidence, the maximum TOSHI, the maximum acute HQ, the extent and distribution of cancer and noncancer risks in the exposed population, multipathway risks, and the risk estimation uncertainties.

Since proposal, our determinations regarding risk acceptability, ample margin of safety, or adverse environmental effects have not changed. However, after proposal, commenters provided updated information on their facilities, including specific information regarding use of the TCEQ modeling guidelines to calculate effective flare stack parameters. We updated the risk assessment for the SOCMI and Neoprene Production source categories considering the comments received on modeling flares. The revised risk assessment (see the risk reports, Residual Risk Assessment for the SOCMI Source Category in Support of the 2024 Risk and Technology Review Final Rule and Residual Risk Assessment for the Polymers & Resins I Neoprene Production Source Category in Support of the 2024 Risk and Technology Review Final Rule, which are available in the docket for this rulemaking) shows that, after application of controls finalized in this rulemaking, the MIR for each of the source categories is 100-in-1 million. Therefore, after application of the EtO-specific controls for process vents, storage vessels, equipment leaks, heat exchange systems, and wastewater, and the requirements to reduce EtO emissions from maintenance vents and PRDs, we find that the risks are acceptable for the SOCMI source category and that the final HON standards will achieve an ample margin of safety to protect human health from risks presented by HON emission sources. Also, after application of the chloroprene-specific controls for process vents, storage vessels, and wastewater, and the requirements to reduce chloroprene emissions from maintenance vents and PRDs, we find that the risks are acceptable for the Neoprene Production source category and that the final P&R I standards will achieve an ample margin of safety to protect human health from risks presented by neoprene production emission sources.

B. Technology Review for the SOCMI, P&R I, and P&R II Source Categories NESHAP and NSPS Review for the SOCMI Source Category

1. What did we propose pursuant to CAA section 112(d)(6) for SOCMI, P&R I, and P&R II source categories and CAA section 111(b)(1)(B) for the SOCMI source category?

a. NESHAP

Based on our technology review for the SOCMI, P&R I, and P&R II source categories, we proposed under CAA section 112(d)(6) changes to the HON and P&R I standards for heat exchange systems, storage vessels, and process vents and we proposed no change under CAA section 112(d)(6) to the P&R II standards for storage vessels and process vents. The P&R II NESHAP currently does not regulate HAP emissions from heat exchange systems, but we are finalizing, as proposed, requirements in the P&R II NESHAP for heat exchange systems pursuant to CAA section 112(d)(2) and (3). In addition, we proposed no change under CAA section 112(d)(6) for transfer racks, wastewater streams, and equipment leaks. We also proposed fenceline monitoring requirements under CAA section 112(d)(6). We provide a summary of our findings, as proposed, in this section.

i. Heat Exchange Systems

In our technology review for the SOCMI, P&R I, and P&R II source categories, we identified one development in practices and processes for HON and P&R I heat exchange systems, the use of the Modified El Paso Method for monitoring for leaks from heat exchange systems. We determined that this method is more effective in identifying leaks and measures a larger number of compounds than the methods previously required in the HON and the P&R I NESHAP. After evaluating state and Federal regulations requiring the Modified El Paso Method, as well as emission data collected for the Ethylene Production RTR (refer to section II.D of the proposal preamble (88 FR 25080, April 25, 2023) and the Ethylene Production RTR rulemaking docket, Docket ID No. EPA-HQ-OAR-2017-0357), we proposed pursuant to CAA section 112(d)(6) to require use of the Modified El Paso Method with a leak definition of 6.2 ppmv of total strippable hydrocarbon concentration (as methane) in the stripping gas to further reduce HAP emissions from both new and existing heat exchange systems, as well as to disallow delay of repair of leaks if the measured concentration meets or exceeds 62 ppmv. Based on an evaluation of incremental HAP cost effectiveness to increase the monitoring frequency, we proposed no changes to the monitoring frequency previously required under the HON and the P&R I NESHAP for monitoring for leaks from heat exchange systems, which continues to be monthly monitoring in the first 6 months following startup of a source and quarterly monitoring thereafter. We also proposed to require re-monitoring at the monitoring location where a leak is identified to ensure that any leaks found are fixed. Further, we proposed that none of these proposed requirements for heat exchange systems apply to heat exchange systems that have a maximum cooling water flow rate of 10 gallons per minute or less. Finally, we proposed that owners and operators may use the current leak monitoring requirements for heat exchange systems at 40 CFR 63.104(b) in lieu of using the Modified El Paso Method provided that 99 percent by weight or more of the organic compounds that could leak into the heat exchange system are water soluble and have a Henry's Law Constant less than 5.0E-6 atmospheres-cubic meters/mol at 25 degrees Celsius. Refer to section III.C.1 of the proposal preamble (88 FR 25080, April 25, 2023) for a summary of our rationale for selecting the proposed leak method, leak definition, and limitation on delay of repairs, as well as our rationale for retaining the previous monitoring schedule.

For a detailed discussion of the EPA's findings, refer to the document titled Clean Air Act Section 112(d)(6) Technology Review for Heat Exchange Systems Located in the SOCMI Source Category that are Associated with Processes Subject to HON and for Heat Exchange Systems that are Associated with Processes Subject to Group I Polymers and Resins NESHAP; and Control Option Impacts for Heat Exchange Systems that are Associated with Processes Subject to Group II Polymers and Resins NESHAP (see Docket Item No. EPA-HQ-OAR-2022-0730-0075).

ii. Storage Vessels

In our technology review for the SOCMI, P&R I, and P&R II source categories, we identified three options for reducing emissions from HON and P&R I storage vessels. Refer to section III.C.2 of the proposal preamble (88 FR 25080, April 25, 2023) for a summary of the three options. Based on our evaluation of the costs and emission reductions of each of the three options, we proposed pursuant to CAA section 112(d)(6) to: (1) Revise the Group 1 HON and P&R I storage vessel capacity and MTVP thresholds to reflect the MON existing source threshold, which requires existing storage vessels between 38 m and 151 m with a vapor pressure greater than or equal to 6.9 kilopascals to reduce emissions of organic HAP by 95 percent utilizing a closed vent system and control device, or reduce organic HAP emissions by utilizing either an IFR, or an EFR, by routing the emissions to a process or a fuel gas system, or by vapor balancing; and (2) in addition to requirements specified in option 1, require upgraded deck fittings and controls for guidepoles for all storage vessels equipped with an IFR as already required in 40 CR 63, subpart WW.

For a detailed discussion of the EPA's findings, refer to the document titled Clean Air Act Section 112(d)(6) Technology Review for Storage Vessels Located in the SOCMI Source Category that are Associated with Processes Subject to HON, Storage Vessels Associated with Processes Subject to Group I Polymers and Resins NESHAP, and Storage Vessels Associated with Processes Subject to Group II Polymers and Resins NESHAP (see Docket Item No. EPA-HQ-OAR-2022-0730-0073).

iii. Process Vents

In our technology review for the SOCMI, P&R I, and P&R II source categories, we identified three options for reducing emissions from HON process vents and P&R I continuous front-end process vents. Refer to section III.C.3.a of the proposal preamble (88 FR 25080, April 25, 2023) for a summary of the three options. Based on our evaluation of the costs and emission reductions of each of the three options, we proposed pursuant to CAA section 112(d)(6) to revise the process vent applicability threshold to redefine a HON Group 1 process vent and P&R I Group 1 continuous front-end process vent (requiring control) as any process vent that emits greater than or equal to 1.0 lb/hr of total organic HAP. We also proposed removing the TRE concept in its entirety and removing the 50 ppmv and 0.005 scmm Group 1 process vent thresholds. In addition, we identified one option for reducing emissions from P&R I batch front-end process vents and we proposed pursuant to CAA section 112(d)(6) to revise the process vent applicability threshold to redefine a P&R I Group 1 batch front-end process vent as a process vent that releases total annual organic HAP emissions greater than or equal to 4,536 kg/yr (10,000 lb/yr) from all batch front-end process vents combined.

For a detailed discussion of the EPA's findings, refer to the document titled Clean Air Act Section 112(d)(6) Technology Review for Continuous Process Vents Located in the SOCMI Source Category that are Associated with Processes Subject to HON, Continuous Front-end and Batch Front-end Process Vents Associated with Processes Subject to Group I Polymers and Resins NESHAP, and Process Vents Associated with Processes Subject to Group II Polymers and Resins NESHAP (see Docket Item No. EPA-HQ-OAR-2022-0730-0094).

iv. Fenceline Monitoring

We proposed a fenceline monitoring standard for the SOCMI and P&R I source categories requiring owners and operators to monitor for any of six specific HAP ( i.e., benzene, 1,3-butadiene, ethylene dichloride, vinyl chloride, EtO, and chloroprene) if their site uses, produces, stores, or emits any of them, and conduct root cause analysis and corrective action upon exceeding the annual average concentration action level set forth for each HAP.

b. NSPS

i. Process Vents

In our review of NSPS subparts III, NNN, and RRR (for SOCMI air oxidation units, distillation operations, and reactor processes, respectively), we identified certain advances in process operations that were not identified or considered during development of the original NSPS. Refer to section III.C.3.b of the proposal preamble (88 FR 25080, April 25, 2023) for a detailed summary of these advances in process operations. Based on our evaluation of statutory factors, including costs and emission reductions, we proposed pursuant to CAA section 111(b)(1)(B) revised NSPS subparts IIIa, NNNa, and RRRa (which are applicable to affected facilities for which construction, reconstruction, or modification commences after April 25, 2023). We proposed that the revised NSPS subparts encompass a suite of process vent requirements, which include: (1) Removing the TRE index value concept in its entirety and instead requiring owners and operators to reduce emissions of TOC (minus methane and ethane) from all vent streams of an affected facility ( i.e., SOCMI air oxidation unit processes, distillation operations, and reactor processes for which construction, reconstruction, or modification commences after April 25, 2023) by 98 percent by weight or to a concentration of 20 ppmv on a dry basis corrected to 3 percent oxygen, or combust the emissions in a flare meeting the same operating and monitoring requirements for flares that we are finalizing for flares subject to the HON; (2) eliminating the relief valve discharge exemption from the definition of “vent stream” such that any relief valve discharge to the atmosphere of a vent stream is a violation of the emissions standard; (3) prohibiting an owner or operator from bypassing the APCD at any time, and requiring the owner or operator to report any such violation (including the quantity of TOC released to the atmosphere); (4) requiring that flares used to reduce emissions comply with the same flare operating and monitoring requirements as those we have promulgated for flares used in SOCMI-related NESHAP; (5) requiring work practice standards for maintenance vents during startup, shutdown, maintenance, or inspection of any of the air oxidation units, distillation operations, and reactor processes affected facilities under the applicable NSPS where the affected facility is emptied, depressurized, degassed, or placed into service; and (6) adding control device operational and monitoring requirements for adsorbers that cannot be regenerated and regenerative adsorbers that are regenerated offsite. For a detailed discussion of the EPA's findings, refer to the document titled CAA 111(b)(1)(B) review for the SOCMI air oxidation unit processes, distillation operations, and reactor processes NSPS subparts III, NNN, and RRR (see Docket Item No. EPA-HQ-OAR-2022-0730-0011).

ii. Equipment Leaks

In our review of NSPS subpart VVa (for SOCMI equipment leaks), we identified emission reduction measures used in practice related to LDAR of certain equipment that achieve greater emission reductions than those currently required by NSPS subpart VVa. Refer to section III.C.6.b of the proposal preamble (88 FR 25080, April 25, 2023) for a summary of these measures. Based on our evaluation of statutory factors, including costs and emission reductions, we proposed pursuant to CAA section 111(b)(1)(B) a revised NSPS subpart VVb applicable to affected facilities for which construction, reconstruction, or modification commences after April 25, 2023. The revised NSPS VVb includes the same requirements as in NSPS subpart VVa plus a requirement that all gas/vapor and light liquid valves be monitored monthly at a leak definition of 100 ppm and all connectors be monitored once every 12 months at a leak definition of 500 ppm.

For a detailed discussion of the EPA's findings, refer to the document titled CAA 111(b)(1)(B) review for the SOCMI Equipment Leaks NSPS Subpart VVa (see Docket Item No. EPA-HQ-OAR-2022-0730-0096).

2. How did the technology review change for the SOCMI, P&R I, and P&R II source categories, and NSPS review change for the SOCMI source category?

We are finalizing the results of the NSPS review under CAA section 111(b)(1)(B) for the SOCMI source category as proposed (88 FR 25080, April 25, 2023), with a change to the definition of “capital expenditure” in NSPS subpart VVb to use a formula that better reflects the trajectory of inflation. We are also finalizing the results of the technology review pursuant to CAA section 112(d)(6) for the SOCMI, P&R I, and P&R II source categories as proposed (88 FR 25080, April 25, 2023), with some changes to the fenceline monitoring requirements that we proposed under the technology review for the SOCMI and P&R I source categories, and also a minor change to clarify that, with regard to the storage vessel portion of the technology review, the Group 1 HON and P&R I storage vessel capacity and MTVP thresholds apply to both new and existing sources. For fenceline monitoring requirements, the final rule establishes two action levels for chloroprene ( i.e., one action level under CAA section 112(d)(6) and another action level under CAA section 112(f)) in lieu of only one action level for this HAP, as proposed. We are also finalizing: (1) Burden reduction measures to allow owners and operators to skip fenceline measurement periods for specific monitors with a history of measurements that are at or below certain action levels; (2) a clarification that fenceline monitoring is required for owners and operators with affected sources that produce, store, or emit one or more of the target analytes; (3) a reduction in the requirements for the minimum detection limit of alternative measurement approaches; (4) clarifications on establishing the monitoring perimeter for both sorbent tubes and canisters; (5) clarifications on the calculation of Δc when a site-specific monitoring plan is used to correct monitoring location concentrations due to offsite impacts; (6) a change in the required method detection limit for alternative test methods from an order of magnitude below the action level to one-third of the action level; and (7) with the exception of fenceline monitoring of chloroprene at P&R I affected sources producing neoprene, a change in the compliance date in the final rule to begin fenceline monitoring 2 years (instead of 1 year, as proposed) after the effective date of the final rule. For P&R I affected sources producing neoprene, we have changed the compliance date for fenceline monitoring of chloroprene to begin no later than October 15, 2024, or upon startup, whichever is later, subject to the owner or operator seeking the EPA's authorization of an extension of up to 2 years from July 15, 2024.

3. What key comments did we receive on the technology review and NSPS review, and what are our responses?

a. NESHAP

The EPA received comments in support of and against the proposed technology review. We received only minor comments requesting clarifications associated with our technology review for heat exchange systems and storage vessels. The comments and our specific responses to these issues can be found in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking. Based on these comments, we are finalizing revisions to require the Modified El Paso Method for heat exchange systems, and we are finalizing revisions to the Group 1 HON and P&R I storage vessel capacity and MTVP thresholds to reflect the MON existing source threshold for both new and existing sources.

We did not receive any comment with regard to the technology review for transfer racks and wastewater streams. Furthermore, for equipment leaks, the comments were generally either supportive of the determination that no cost-effective developments from the technology review were found, or that the Agency should re-open and reevaluate the MACT standards for new technologies. Based on our review of the comments received for equipment leaks, we are finalizing our determination that no cost-effective developments exist and that it is not necessary to revise these emission standards under CAA section 112(d)(6). For process vents, the EPA received additional information from commenters on costs necessary for control of process vents that emit greater than or equal to 1.0 lb/hr of total organic HAP. We also received several comments regarding the fenceline monitoring requirements that we proposed under the technology review. This section provides summaries of and responses to the key comments received regarding: (1) The technology review amendments we proposed for HON process vents and P&R I continuous front-end process vents, and (2) the proposed fenceline monitoring requirements. Comment summaries and the EPA's responses for additional issues raised regarding the proposed requirements resulting from our technology review for the SOCMI, P&R I, and P&R II source categories are in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

i. Process Vents

Comment: A commenter said they supported the EPA's proposed rule text at 40 CFR 63.113(a)(4) and 40 CFR 63.485(l)(6), (o)(6), (p)(5), and (x) that removes the TRE concept in its entirety from both the HON and P&R I NESHAP. However, numerous commenters opposed removal and provided the following arguments to reinforce their opposition:

• The EPA lacks the statutory authority to remove the TRE index value concept because it has offered no supportable basis as to why removal would constitute a development in practices, processes, or technologies under CAA section 112(d)(6).
• The fact that another source category's standards do not include the TRE index value concept is not a development in practice, and the EPA offered no argument as to how it could possibly fit within that box.
• The fact that some facilities choose to control process vents that would be exempt using the TRE index value does not indicate that removing the TRE concept is a development in practices, processes, or technologies. Electing not to use the TRE is a business choice, not a technological development.
• Complexity of an established compliance tool is not a technological development.
• The EPA has not adequately supported its proposal to remove the TRE concept.
• While it is true that certain facilities may have designated process vents with a TRE index value above 1.0 as a Group 1 process vent, the reason behind this may not necessarily be voluntary or driven by the desire to avoid the TRE calculation, but rather facilities may be controlling these process vents to comply with state or local regulations regarding VOCs or to meet a best available control technology (BACT) limit.
• The EPA's rationale for eliminating the TRE index value from the HON rule due to variations in other MACT rules is flawed given that the EPA did not remove the TRE index value during the revision of the MON rule and distinguishing between Group 1 and Group 2 process vents in the Ethylene Production source category is irrelevant.
• Even though some process vents with a TRE index value above 1.0 are controlled at certain facilities, that does not imply that controlling all process vents with TRE index values above 1.0 is appropriate or cost-effective.
• Facilities often use source test results to determine TRE calculation inputs (even for vent streams with a TRE index value greater than 4.0), and this approach is neither complex nor uncertain to interpret.
• Despite the EPA's assertion that enforcing the TRE index value “can be” arduous due to its theoretical nature, no instances have been provided where verifying a TRE index value calculation posed challenges for an agency or contradicted actual cost effectiveness at a facility. The number of inputs to the TRE index value calculation is proportional to the number of measurable organic compounds in the vent stream; and some facilities have very few organic compounds in process vents, so the inputs are minimal, and if those inputs are determined by other allowed methods (e.g., source tests, permit limits), then verification of these inputs is clearly not problematic.
• Perceived complexity is not a basis for removing the option.
• The TRE index value has been an integral part of many technology-based air standards since its initial development, serving as a mechanism for determining cost effectiveness and triggering the requirements for process vent control (see,e.g., the preamble to the 1994 HON adoption, which states that the TRE concept is appropriate because it “can be used to reflect all possible combinations of various factors that affect emission rates and likelihood of current control” (59 FR 19416) and “would provide consistency between the HON[,] the recently issued [control techniques guidelines] for SOCMI process vents. . .[and] the applicability criteria for the three SOCMI process vents NSPS” (59 FR 19418)).
• By considering the TRE index value, an owner or operator can allocate their resources more efficiently and concentrate efforts and resources on the vents that have the greatest potential for emission reduction, maximizing the overall environmental benefit. The TRE considers not only the organic HAP emissions but also the volumetric flow and net heating value of the vent gas stream, and thus it takes into consideration the practicality of controlling relatively small organic HAP emission streams using control devices like a flare or a vapor incinerator.
• Use of the TRE index value is a holistic approach that ensures that the most significant emission sources are targeted for control, leading to more effective pollution reduction.
• Uncontrolled Group 2 process vent gas streams typically exhibit minimal emissions of HAP and VOC, possess a low net heating value, may contain steam or water vapor, and have varying volumetric flow rates. Directing these streams to an emission control device, if available in the CMPU capable of handling them, is a complex engineering problem and would yield negligible emissions reductions. Moreover, it would likely necessitate the addition of significant amounts of supplemental fuel to combust this type of stream and consequently result in additional emissions of carbon monoxide (CO), nitrogen oxides (NO_X), and CO₂ to control a relatively small quantity of HAP or VOC emissions.
• It is not clear how the emissions averaging program, as it is currently applied under the HON, can continue to exist with the requirement to control process vents that are currently designated as Group 2 vents. The burden of over-control to generate “credits” will effectively render the provisions unattainable or useless.
• Many facilities will still be required to comply with TRE-based determinations according to their title V operating permits and requirements under NSPS subparts NNN and RRR.

Many of the commenters who opposed removing the TRE index value in its entirety suggested that the EPA could potentially consider raising the TRE index value threshold, such as by aligning it with the value in the MON rule or the value indicated in Option 3 of the proposed rule, or by setting it at a level agreed upon as cost-effective by the industry. Other commenters opposed this suggestion.

Response: The EPA acknowledges commenters' support for and opposition to the removal of the TRE concept from the HON at 40 CFR 63.113(a)(4) and from the P&R I NESHAP at 40 CFR 63.485(l)(6), (o)(6), (p)(5), and (x). We are finalizing the removal of the TRE concept as proposed. We stand by the rationale we provided in the preamble to the proposed rule (88 FR 25080, April 25, 2023) for removing the TRE concept: (1) We identified at least one more recent (than the HON and the P&R I NESHAP) chemical manufacturing NESHAP ( i.e., ethylene production) that does not use the TRE index value as criteria for determining whether a process vent should be controlled; (2) based on the responses to our CAA section 114 request, we observed that some facilities are controlling continuous process vents that are not required by the HON and the P&R I NESHAP to be controlled per the results of the TRE index value calculation; (3) based on the responses to our CAA section 114 request, we observed that facilities are routing multiple continuous process vents to a single APCD; (4) determining a TRE index value for certain process vent streams is often theoretical, can be extremely complicated, and is uncertain; and (5) because the TRE index value is largely a theoretical characterization tool, it can be very difficult to enforce.

We disagree with commenters that the removal of the TRE concept does not constitute a development in practices, processes, or technologies under CAA section 112(d)(6). We noted in the preamble to the proposed rule (88 FR 25080, April 25, 2023) that some owners and operators do not use the TRE index value to determine whether a vent stream is a Group 1 or Group 2 process vent. While we agree with commenters that owners and operators control Group 2 vent streams for reasons other than the desire to avoid the TRE calculation, the fact is that owners and operators are controlling HON and P&R I Group 2 process vents (possibly to comply with state or local regulations regarding VOCs or to meet a BACT limit), which we consider a development under CAA section 112(d)(6). Given that the TRE concept, as some commenters pointed out, has been used since the original 1994 HON adoption (and even in the 1992 proposed HON rule), we consider owners and operators controlling HON and P&R I Group 2 process vents to be an operational procedure that was not identified or considered during development of the original MACT standards. Additionally, the removal of the TRE concept simplifies the determination as to whether owners and operators must control a vent stream and thus the applicability process is easier to implement.

We disagree with commenters' assertion that the EPA did not provide evidence that the TRE concept is largely theoretical and, as a result, difficult to verify. As identified in the document titled Clean Air Act Section 112(d)(6) Technology Review for Continuous Process Vents Located in the SOCMI Source Category that are Associated with Processes Subject to HON, Continuous Front-end and Batch Front-end Process Vents Associated with Processes Subject to Group I Polymers and Resins NESHAP, and Process Vents Associated with Processes Subject to Group II Polymers and Resins NESHAP (Docket Item ID No. EPA-HQ-OAR-2022-0730-0094), one facility that received the CAA section 114 request provided over 300 pages of modeled runs used to determine certain characteristics of their continuous process vents to be utilized as part of the TRE index value calculations. Reviewing this information revealed that in many cases the facility struggled to unify the modeled runs with actual conditions at the facility and in some cases made arbitrary decisions to allow the model to function. While we agree with commenters that the TRE index value can be derived from less theoretical methods, other responses to the CAA section 114 request did not indicate how parameters used in the TRE index value calculations were determined, and commenters did not provide sufficient information to show which methods were most common throughout industry. Given the theoretical nature of the TRE index value, the EPA maintains that verifying TRE index values is arduous because it can involve relying on significant process knowledge in order to confirm HAP compositions of vent streams, vent stream flowrates, vent stream net heating values, and hourly emissions. It may also require verification of other facility assumptions ( e.g., operational conditions and constraints) especially if modeling was used.

We agree with commenters that the TRE index value has been an integral part of many technology-based air standards since its initial development. In fact, we said as much in the document titled Clean Air Act Section 112(d)(6) Technology Review for Continuous Process Vents Located in the SOCMI Source Category that are Associated with Processes Subject to HON, Continuous Front-end and Batch Front-end Process Vents Associated with Processes Subject to Group I Polymers and Resins NESHAP, and Process Vents Associated with Processes Subject to Group II Polymers and Resins NESHAP (Docket Item ID No. EPA-HQ-OAR-2022-0730-0094). The TRE concept is almost 40 years old as it was first introduced in a December 1984 EPA document (EPA-450/3-84-015; see attachment to Docket Item No. EPA-HQ-OAR-2022-0730-0094). However, even if it has been integral, certain aspects of its underlying development are clearly no longer applicable or appropriate. For example, the EPA stated in the 1984 supporting materials (EPA-450/3-84-015) that the Agency attempted to make the TRE index independent of inflation ( e.g., the EPA assumed fixed relative costs of various resources, such as carbon steel and electricity), yet it is impossible to ignore inflation in the TRE calculations due to the time that has passed since it was developed ( e.g., costs of carbon steel and electricity have undoubtedly increased since the development of the TRE index).

Although the TRE index value may allow owners and operators to allocate resources efficiently and ensure that the most significant emission sources are targeted for control, the current use of the TRE index value is only based on controlling a single process vent with a single APCD. This is an unrealistic scenario when compared to how chemical manufacturing facilities actually control their process vents; and it is much more likely that a facility routes numerous process vents to the same APCD (and this is evident from observing the responses to our CAA section 114 request).

We agree with commenters that the removal of the TRE concept may lead to emissions increases due to the use of supplemental fuel in new APCDs that are potentially needed to control Group 2 streams that are currently uncontrolled; and we acknowledged this in our preamble to the proposed rule (88 FR 25080, April 25, 2023) as well as in the RIA accompanying the proposal. However, based on other comments received and discussed elsewhere in this section of this document (regarding the use of low volumetric flow rates in our original proposed cost estimate), we revised our cost analysis to account for higher flow rates to the APCD. As a result of this flow rate adjustment, additional supplemental fuel was needed to control Group 2 vent streams that exhibit minimal emissions of HAP and VOC, possess a low net heating value, and may contain steam or water vapor. Even so, at proposal, we overestimated the amount of supplemental fuel that would be needed nationwide (168 MMscf/yr) to control Group 2 vent streams that exhibit minimal emissions of HAP and VOC, and we continue to believe this estimate is conservatively high even after revising our cost analysis. For this reason, we are not revising our estimate of secondary impacts (including emissions of CO, CO₂, NO_X (including nitrous oxide (N₂ O)), particulate matter, and sulfur dioxide (SO₂)).

With regard to the commenters' assertion that many facilities will still be required to comply with TRE-based determinations according to their title V operating permits and requirements under NSPS subparts NNN and RRR, we note that we are simplifying the HON overlap provisions for NSPS subparts III, NNN, and RRR in the final rule ( i.e., we are finalizing, as proposed, that pursuant to 40 CFR 63.110(d)(1), (d)(4), (d)(7), and (d)(10) process vents subject to the emission standards in HON that are also subject to the NSPS subpart III, NNN, and/or RRR are only required to comply with the HON). Also, facilities already have general obligations under title V reopening for cause and 5-year renewals to ensure that permits include all requirements applicable to a facility.

Concerning emissions averaging, we note that the provisions experienced no significant changes as a result of removing the TRE concept. The only explicit references to the TRE concept as part of the emissions averaging provisions are at 40 CFR 63.150(g)(2)(iii)(B)(2) with respect to a vent transitioning from a Group 1 process vent to a Group 2 process vent and at 40 CFR 63.150(m)(2)(i) related to obligations associated with carbon absorbers, adsorbers, or condensers not equipped with a control device. Both of these references are captured as no longer being required at 40 CFR 63.113(a)(4)(xii) and 40 CFR 63.113(a)(4)(xiii), respectively, and do not affect applicability. Emissions averaging has always been an optional provision with its burden falling on owners or operators to decide if it was appropriate or cost-effective to over-control certain streams while under-controlling other streams. This does not change as a result of redefining Group 2 process vents to be those streams containing less than 1.0 lb/hr of HAP. In addition, we note that credits may be generated from controlling Group 1 process vents at a higher nominal efficiency than the reference technology and from utilizing pollution prevention measures either independently or in combination with Group 1 process vents as specified at 40 CFR 63.150(c). Thus, even if a facility determines that controlling Group 2 process vents is infeasible, there are other avenues to pursuing the emission averaging provisions.

Finally, we disagree with the commenters' suggestion to raise the TRE index value threshold. Regarding a commenter's assertion that removing the TRE concept is flawed given that no action was taken on the TRE concept in the MON RTR, we note that we did not have data related to Group 2 process vents while developing revisions to the MON. Setting an emission threshold with no knowledge as to which Group 2 MON vent streams would be impacted and without knowing the potential cost or reductions associated with that revision would not have been appropriate. Thus, we did not identify any cost-effective developments in practices, processes, or control technologies for process vents. However, as part of this rulemaking, the Group 2 process vent data was collected via a CAA section 114 request. Our analysis of the Group 2 process vent data shows that removing the TRE concept and installing a 1.0 lb/hr of HAP emission threshold is of a similar cost effectiveness to raising the TRE index value to 5.0. However, for the reasons stated earlier in this document, removing the TRE concept was selected. Given that we determined that a TRE index value of 5.0 was cost effective but opted to remove the TRE concept instead, it would be unreasonable to finalize a TRE index value of 3.0 based on the considerations discussed above and the decreased potential impact.

Comment: Commenters said they opposed the EPA's proposed rule text at 40 CFR 63.101 and 40 CFR 63.113(a)(1) and (2) that would remove the 50 ppmv and 0.005 scmm Group 1 process vent thresholds from the Group 1 process vent definition and that would instead require owners and operators of process vents that emit greater than or equal to 1.0 lb/hr of total organic HAP to either reduce emissions of organic HAP using a flare meeting the proposed operating and monitoring requirements for flares in NESHAP subpart F or reduce emissions of total organic HAP or TOC by 98 percent by weight or to an exit concentration of 20 ppmv.

A commenter requested that the EPA explain how it arrived at a 1 lb/hr control threshold. The commenter said that while the simplicity of a 1 lb/hr threshold is admittedly appealing, it is overly simplistic, and because the EPA did not supply any justification for the choice of 1 lb/hr, it appears to be an arbitrary and capricious threshold value.

Another commenter requested that if the EPA decides to keep the proposed Group 1 process vent definition with the 1.0 lb/hr total organic HAP mass flow rate threshold, then these proposed revisions should apply only to new sources in the HON. The commenter asserted that facilities with new sources will have greater flexibility in selecting cost-effective control options during the design and construction phase than the very limited, and climate impacting, options available to retrofit existing sources. The commenter added that additional controls would have virtually no effect on improving ample margin of safety or additional protection of public health.

Response: Commenters did not provide sufficient information detailing why requiring the control of process vents that emit greater than 1.0 lb/hr of total organic HAP would be infeasible beyond the arguments related to the removal of the TRE concept which are addressed in response to another comment in this section of this preamble. Consequently, we are finalizing rule text, as proposed at 40 CFR 63.101 and 40 CFR 63.113(a)(1) and (2), that removes the 50 ppmv and 0.005 scmm Group 1 process vent thresholds from the Group 1 process vent definition and instead requires owners and operators to control process vents that emit greater than or equal to 1.0 lb/hr of total organic HAP.

We disagree with the commenters' contention that the 1.0 lb/hr of total organic HAP threshold is arbitrary and capricious. As stated in the preamble to the proposed rule (88 FR 25080, April 25, 2023), we arrived at the 1.0 lb/hr of total organic HAP threshold using detailed information for 50 Group 2 continuous process vents that was provided by 9 of the 13 HON facilities (including 1 P&R I facility collocated with a HON facility) that received the CAA section 114 request.

We started by performing an analysis of the 50 Group 2 continuous process vents for a simple control scenario. Using vent stream flowrates, vent stream net heating values, VOC and HAP emission rates (which we obtained from TRE index value calculations that facilities provided in their response to the CAA section 114 request), and the methodology from the sixth edition of the EPA Air Pollution Control Cost Manual; we calculated a cost for installing ductwork and a blower on each vent, assuming each of these vents could be routed to an existing control device achieving 98 percent by weight emission reduction. Given that many of the Group 2 continuous process vents have a very low flow rate and/or emission rate, we found that even installing simple ductwork and a blower would not be cost-effective for the majority of these vents. However, we did identify 23 of these Group 2 continuous process vents (a subset of the 50 Group 2 process vents from responses to our CAA section 114 request) for which we found this scenario to be cost-effective ( i.e., $1,100 per ton of VOC/HAP or less).

We then reviewed mass flow rates of total organic HAP within this subset of Group 2 continuous process vents to develop two different thresholds ( i.e., 0.10 lb/hr and 1.0 lb/hr) for consideration. We estimated that 48 HON facilities operating 287 HON Group 2 process vents (96 of which are already voluntarily controlled and 191 that are not currently controlled) and 3 P&R I facilities operating 30 P&R II Group 2 continuous front-end process vents (in which all 30 are not currently controlled) would be impacted if we implemented a 0.10 lb/hr total organic HAP mass flow rate threshold. Conversely, only 16 HON facilities operating 48 HON Group 2 process vents (32 of which are already voluntarily controlled and 16 that are not currently controlled) and 3 P&R I facilities operating 9 P&R I Group 2 continuous front-end process vents (in which all 9 are not currently controlled) would be impacted if we implemented a 1.0 lb/hr total organic HAP mass flow rate threshold. We then estimated costs to control each Group 2 continuous process vent scenario and ultimately concluded that only those streams with greater than or equal to 1.0 lb/hr of total organic HAP would be cost-effective to control. The details of this analysis are discussed in the document titled Clean Air Act Section 112(d)(6) Technology Review for Continuous Process Vents Located in the SOCMI Source Category that are Associated with Processes Subject to HON, Continuous Front-end and Batch Front-end Process Vents Associated with Processes Subject to Group I Polymers and Resins NESHAP, and Process Vents Associated with Processes Subject to Group II Polymers and Resins NESHAP (Docket Item ID No. EPA-HQ-OAR-2022-0730-0094).

We also disagree with the commenter that the 1.0 lb/hr of total organic HAP threshold should apply only to new sources in the HON. In response to another comment reflected elsewhere in this section of this preamble, we have determined that the threshold is cost-effective for existing sources.

Finally, with regard to comments suggesting that additional controls would have virtually no effect on improving ample margin of safety or additional protection of public health, we note that these provisions are finalized under the authority of the technology review pursuant to CAA section 112(d)(6), which requires us to revise standards as necessary and does not obligate us to consider health impacts or generate an ample margin of safety.

Comment: Commenters suggested that the EPA significantly underestimated the cost of installing an additional thermal oxidizer and that therefore the cost effectiveness evaluation for removing the TRE concept is not correct. Many of these commenters contended that the fact that a control device has the capability to control multiple process vents does not automatically imply that controlling all vents together is cost-effective in every scenario; if the cumulative emissions from the Group 2 process vents are relatively low, it would not be economically viable to control all of them using a single control device. A commenter said that although it is reasonable to assume that a single new control device will be installed for facilities that will be controlling existing Group 2 process vents with emissions greater than 1.0 lb/hr, the use of 10 scfm for determining a total capital investment (TCI) for the new control device is not representative. The commenter contended that although these vents are expected to have lower volumetric flow rates than many existing Group 1 vents, there are logistical and safety concerns that must be considered when designing a closed vent system and thermal oxidizer that necessitate higher flow rates. The commenter added that there are multiple facilities with more than one of these types of vents per facility; thus, multiple vents will need to be collected into a common system which will correspond to a higher flow rate. The commenter said that a reasonable low-end estimate for a new single thermal oxidizer for controlling these process vents is closer to a $1,000,000 TCI. The commenter also noted that capital costs could range from $5,000,000 to $15,000,000. The commenter added that for facilities that produce chlorinated compounds, this cost would be higher because any new thermal oxidizer will need to be equipped with acid gas and dioxin/furan controls. Another commenter agreed that facilities that produce chlorinated compounds would incur higher costs but contended that additional controls for a facility's Group 2 process vents would cost at least $50,000,000 in engineering and design, equipment, and installation costs.

Another commenter said that for their facility, the addition of a single control device, associated piping, instrumentation, engineering, and installation to control 11 process vents (that are currently considered Group 2 under the HON) will cost $55,000,000, or approximately $925,000/ton of HAPs. Another commenter argued that emission sources that are long distances away from existing control devices ( e.g., a tank in a remote tank farm) and streams not compatible with a facility's existing control equipment are no more economically feasible for additional controls now than when the HON was originally promulgated.

Response: Several commenters provided us with their own capital cost estimates for controlling Group 2 continuous process vents with greater than or equal to 1.0 lb/hr of total organic HAP, resulting in a very wide range of capital costs ( i.e., $1,000,000 to $55,000,000). However, the commenters did not provide information to fully support these capital costs. For example, commenters did not provide the number of streams nor the flow rate for the new streams needing control, did not provide any related emissions reductions from controlling these streams, and did not provide the annual cost for their scenario. As such, it was not possible to fully evaluate the commenters' provided capital cost data.

However, we do agree with commenters that our proposed cost estimate underestimated flow rates needed to route Group 2 continuous process vents with greater than or equal to 1.0 lb/hr of total organic HAP to APCDs. Although we still believe the use of the EPA's control cost template to estimate the cost of installing a new recuperative thermal oxidizer is appropriate (to control a Group 2 continuous process vent with greater than or equal to 1.0 lb/hr of total organic HAP), we revised our estimates to reflect the limitations of the correlations associated with the EPA's control cost template which starts with a flow rate of 500 scfm. With these corrections, we estimate the average TCI to install a new recuperative thermal oxidizer (for both the HON and the P&R I NESHAP) is about $167,000 (as opposed to the $66,000 that we proposed); however, our estimate is still much lower than the wide range of cost estimates provided by commenters. One possible explanation for this difference in cost estimates is that commenters may have used a much higher flow rate ( e.g., 5,000 scfm as opposed to 500 scfm) and a “Regenerative Thermal Oxidizer” in their cost analysis instead of a “Recuperative Thermal Oxidizer.” Moreover, commenters did not provide supporting information for their estimated capital costs, so we do not have a way to corroborate this possible explanation.

In light of the fact that commenters were generally concerned about the cost estimate, we performed additional analyses to evaluate the cost effectiveness of removing the TRE concept from the HON and the P&R I NESHAP. Using a TCI of $1,000,000 as provided by the commenter, and the EPA's control cost template (for installing a new recuperative thermal oxidizer with 70 percent energy recovery), we estimated an annual cost of approximately $330,000 (for the HON) and $318,000 (for the P&R I NESHAP). Applying this annual cost to our estimated number of HON facilities that would need to install a thermal oxidizer and to our estimated HAP emissions reductions for the HON of 538 tpy, we calculated a cost effectiveness of about $9,830 per ton, which we consider to be cost-effective. Applying this annual cost to our estimated number of P&R I facilities that would need to install a thermal oxidizer and to our estimated HAP emissions reductions for the P&R I NESHAP of 130 tpy, we calculated a cost effectiveness of about $7,440 per ton. It is important to note that our analysis considers that 16 HON facilities operating 48 HON Group 2 process vents (32 of which are already controlled by an existing APCD and 16 that are not currently controlled) and 3 P&R I facilities operating 9 P&R I Group 2 continuous front-end process vents (in which all 9 are not currently controlled) would be impacted by the 1.0 lb/hr total organic HAP mass flow rate threshold. We estimated these impacts using the Group 2 process vent data from responses to our CAA section 114 request. As part of our reevaluation, we also revised our HAP emissions reduction estimate for the HON and P&R I process vents that are not currently controlled to reflect the average HAP emissions reductions from the three HON Group 2 process vents and five P&R I Group 2 process vents that would be impacted by the 1.0 lb/hr total organic HAP mass flow rate threshold (based on data from responses to our CAA section 114 request). In our proposal, we took the lowest HAP emission reduction based on a single HON process vent and did not appropriately account for the other HON process vents for which we had data. We corrected a similar issue for the P&R I NESHAP. Therefore, our final calculation for estimating the cost effectiveness for removing the TRE concept in its entirety from the HON includes a total HAP and VOC reduction of 538 tpy (and not 436 tpy as proposed) and for the P&R I NESHAP, a total HAP and VOC reduction of 130 tpy (and not 51 tpy as proposed). It is also possible that the actual emissions reductions may be higher than our estimate because the higher capital costs provided by industry are likely to be for thermal oxidizers that are sized to control higher flow streams with more HAP emissions. For further details on how we revised our estimates of cost and HAP emissions reductions, see the document titled Clean Air Act Section 112(d)(6) Technology Review for Continuous Process Vents Located in the SOCMI Source Category that are Associated with Processes Subject to HON, Continuous Front-end and Batch Front-end Process Vents Associated with Processes Subject to Group I Polymers and Resins NESHAP, and Process Vents Associated with Processes Subject to Group II Polymers and Resins NESHAP—FINAL, which is available in the docket for this rulemaking.

Absent additional detailed information from commenters, we are finalizing the removal of the TRE concept as proposed and are requiring control for process vents that emit greater than or equal to 1.0 lb/hr of total organic HAP. We also believe this is reasonable given that a 1.0 lb/hr total organic HAP mass flow rate threshold for continuous HON and P&R I process vents aligns more closely with the batch process vent control threshold in the MON and the NESHAP for Chemical Manufacturing Area Sources. In each of these NESHAP, the applicability threshold of 10,000 lb/yr per process is used for batch process vents.

Comment: Commenters observed that the EPA's favorable cost-effectiveness outcome is based on emissions reductions that have already occurred and that will not occur as a result of the proposed standards (and thus should not be used in the calculus). The commenters remarked that the EPA's final calculation for estimating the cost effectiveness for removing the TRE concept in its entirety included a total annual cost of $3,150,000 and a HAP and VOC reduction of 436 tpy. The commenters pointed out that process vents that are already voluntarily controlled account for 366 tpy of the total reduction even though they will not have emissions reductions as a result of implementing the new proposed definition of a Group 1 process vent. The commenters argued that if the EPA determines that the emissions reductions from these vents should be included in the analysis, the Agency must account for the entire cost associated with controlling these emissions ( i.e., annual costs associated with operating a thermal oxidizer) rather than only the costs associated with the installation and operation of ductwork and blowers. The commenters added that if there are no emissions reductions expected from process vents that are already voluntarily controlled, then the cost effectiveness analysis should be revised such that it does not include reductions from these vents.

Response: The EPA maintains that the emission reductions associated with removing the TRE concept and redefining Group 1 process vents to include process vents emitting greater than 1.0 lb/hr of HAP are reasonable, and the EPA is not making any revisions as a result of this comment. Commenters are correct in stating that 366 tpy of HAP emitted by HON process vents exceeding 1.0 lb/hr of HAP are already voluntarily controlled. However, the emission reductions are presented on a basis of allowable emissions. Previously, there were no requirements for process vents exceeding 1.0 lb/hr of HAP. Therefore, under the previous rulemaking, all emissions from these vents were allowable, regardless of whether some facilities were voluntarily controlling these emissions or not. By setting the emission threshold of 1.0 lb/hr of HAP, the allowable emissions are restricted, resulting in the 366 tpy of emission reductions that the EPA utilized to determine the cost effectiveness of removing the TRE concept and redefining Group 1 process vents. We note that we updated our total HAP reductions and annual cost estimates in response to a comment reflected elsewhere in this section of this preamble. For details on how we revised our estimate of cost and HAP emissions reductions, see the document titled Clean Air Act Section 112(d)(6) Technology Review for Continuous Process Vents Located in the SOCMI Source Category that are Associated with Processes Subject to HON, Continuous Front-end and Batch Front-end Process Vents Associated with Processes Subject to Group I Polymers and Resins NESHAP, and Process Vents Associated with Processes Subject to Group II Polymers and Resins NESHAP—FINAL, which is available in the docket for this rulemaking.

We also disagree with commenters that annual operating costs should be considered for the control devices that are controlling the voluntarily controlled streams. These existing control devices are controlling other streams that are regulated ( e.g., controlling HON Group 1 process vents), thus the control devices would continue operating regardless of whether the Group 2 streams are sent to them or not.

Comment: Commenters requested that the EPA add EPA Method 320 to 40 CFR 63.115(g)(2) and (3) and allow companies to use measurements or testing conducted within the last 5 years to initially demonstrate that a process vent is a Group 2 process vent under 40 CFR 63.115(g) provided that: (1) The prior measurement or test was conducted using the same methods specified in 40 CFR 63.115(g), and (2) either no process changes have been made since the test, or the owner or operator can demonstrate that the results of the measurement or test, with or without adjustments, reliably demonstrate compliance with 40 CFR 63.115(a) despite process changes.

A commenter also requested that the EPA allow companies to use engineering calculations or process knowledge to initially demonstrate that a process vent is a Group 2 process vent under 40 CFR 63.115(g). The commenter pointed out that they already conducted testing and sampling procedures on their emission points corresponding to the EPA's CAA section 114 request which cost $20,000 to $30,000 for a single process vent. The commenter added that testing every vent stream is not necessary where an owner or operator has engineering calculations or process knowledge to demonstrate that a vent stream is a Group 2 process vent; and historically, under the group determination procedures for process vents, the owner or operator of a Group 2 process vent with a TRE index value greater than 4.0 could use measurements, engineering assessments, and calculations to determine the TRE index value of the vent stream. The commenter also said that one of their facilities continuously monitors vent flow and HAP concentration from two HON process vents when they are routed to atmosphere and uses the calculated TRE index value to demonstrate that the vents remain Group 2 on an ongoing basis. The commenter said that this alternative monitoring approach was requested and approved due to the variability of HAP emissions from those vents; and generally, the calculated TRE index value remains well above 5.0. The commenter claimed that this alternative monitoring is used when the site thermal oxidizer is down for preventive maintenance; and meeting the proposed new process vent requirements would require either a significant investment in new control equipment or shutdown of the process during thermal oxidizer maintenance.

Response: We are revising the final rule based on the commenter's request to add EPA Method 320 to 40 CFR 63.115(g)(2) and (3) and allow for certain previously conducted performance tests to be exempt from the Group 2 demonstration requirements at 40 CFR 63.115(g) provided the owner or operator can demonstrate: (1) No changes have been made to the process since the time of the previously conducted measurement or emission test; (2) the previously conducted measurement or emission test was conducted using the same methods specified in 40 CFR 63.115(g); and (3) the previously conducted measurement or emission test was completed within the last 60 months. However, we disagree with the commenters' request to allow companies to use engineering calculations or process knowledge to initially demonstrate that a process vent is a Group 2 process vent under 40 CFR 63.115(g). As with our concerns relative to the TRE index value, the ability to use assessments leads to greater uncertainty with regard to characterization of vent streams and their emission potential. We note that as explained in section IV.C.3.e of this preamble, we are finalizing language in the “C” and “Q” terms of the equations at 40 CFR 63.115(g)(3)(ii) and (g)(4)(iv) allowing the use of engineering calculations to determine concentration or flow rate only in situations where measurements cannot be taken with EPA reference methods.

ii. Fenceline Monitoring

Comment: Numerous commenters supported the EPA's proposal to require fenceline monitoring at facilities in the SOCMI and P&R I source categories that use, produce, store, or emit benzene, 1,3-butadiene, chloroprene, EtO, ethylene dichloride, or vinyl chloride. These commenters also said they support the requirement to conduct root cause analysis and corrective action. In addition, some commenters voiced their support for requiring monitoring data to be made available to the public in the WebFIRE database, allowing communities to have access to information that impacts them. Some commenters said the fenceline monitoring technology has proven to be a valuable tool for petroleum refineries to timely detect problems and to address them more quickly, substantially reducing emissions from leaks and other fugitives. At least one commenter said fenceline monitoring can provide numerous benefits, including assisting in identifying an accidental release, and in the event of an accidental release, give the community immediate notice of the emergency and any necessary mitigation responses they should employ (shelter in place, close windows, evacuate, etc.). This commenter added that fenceline monitoring can also: help communities advocate for vigorous enforcement of regulatory requirements; push companies to use safer chemicals; alert and educate friends, family members, and community members; and encourage the media to report on polluting facilities in their areas. The commenter also suggested that facilities can use fenceline monitoring data to take the initiative to improve safety at their operations. Other commenters requested that EtO emissions be required to be monitored by third-party companies. The commenters explained that current laws in some states allow facilities to monitor their own emissions, which could cause underreported emissions.

A commenter argued that fenceline monitoring requirements are crucial in protecting the communities referred to by the commenter as Cancer Alley, especially in St. John the Baptist Parish, which the commenter claimed has the highest cancer rates in the country. The commenter stated that more and more residents are either facing a cancer diagnosis or know someone, such as an immediate family, diagnosed with cancer; and asthma rates and hospitalizations from asthma are ever-increasing, especially amongst children. The commenter also said the area is facing increased weather events brought about by climate change. Citing an analysis by the Times Picayune and Advocate newspapers, the commenter said that 740 toxic sites are at risk from storms, with most of those plants concentrated in the area the commenters refer to as Cancer Alley. The commenter said that after experiencing numerous storms, they personally witnessed the flaring of surrounding plants, including the plants that produce EtO, and are concerned about the increase of pollution before, during, and after weather events.

On the contrary, other commenters opposed the EPA's proposal to require fenceline monitoring at facilities in the SOCMI and P&R I source categories that use, produce, store, or emit benzene, 1,3-butadiene, chloroprene, EtO, ethylene dichloride, or vinyl chloride. These commenters primarily argued that the EPA exceeded its authority under CAA section 112(d)(6) because fenceline monitoring is not a “development[] in practices, processes, and control technologies” for fugitive EtO emissions. Commenters in opposition of fenceline monitoring made the following points about the EPA's assertion of authority to require fenceline monitoring:

• Fenceline monitoring has been in existence for years, but as recently as 2020 the EPA concluded (in the MON in response to Comment 40 in the document titledSummary of Public Comments and Responses for the Risk and Technology Review for Miscellaneous Organic Chemical Manufacturing, see Docket Item No. EPA-HQ-OAR-2018-0746-0200) that they were “not aware of any methodology or technology with the necessary accuracy, precision, and detection sensitivity to require fenceline monitoring for EtO.”
• It is unclear what standard the EPA is reviewing or how fenceline monitoring constitutes a review of the existing standards with respect to “developments in practices, processes, and control technologies.”
• The EPA does not explain how fenceline monitoring, which by itself does not reduce emissions, is a development.
• The EPA does not provide any analysis as to how “root cause analysis and corrective action” are developments with respect to any particular unit/unit type.
• The EPA does not adequately explain how monitoring methods are a development nor does the EPA explain what development category fenceline monitoring allegedly falls into (i.e., a work practice standard that was not considered previously).
• According to the proposed rule, at least in places, fenceline monitoring (coupled with root cause analysis and corrective action) is a work practice standard “that is a development in practices considered under CAA section 112(d)(6) for the purposes of managing fugitive emissions”; however, the EPA considered two monitoring methods—not action levels, root cause analysis, or corrective action—as developments in practices, and it is unclear how monitoring methods fall under any other of the broad categories of developments previously defined by the EPA.
• If the root cause analysis and the corrective action requirements are the work practice standards—as the EPA stated in the proposed NESHAP for EtO commercial sterilization and fumigation operations—then how are monitoring methods a work practice standard? (And if they are not, they are not a development that can be considered under CAA section 112(d)(6)?).
• Adding data quality requirements and existing best practices does not render EPA Method 327 a new development, nor does it remedy the concerns about facilities' ability to accurately measure fenceline EtO concentrations (i.e., there are still no reliable methods that can measure to the level of precision required).
• Coupling fenceline monitoring with a canister monitoring network and a so-called “new” reference method does not transform the fenceline monitoring as proposed into a new technology that is within the CAA section 112(d)(6) authority.

Some of these commenters contended that even if the proposed fenceline monitoring requirements were within the scope of CAA section 112(d)(6) authority, the EPA failed to adequately consider/quantify a level of emission reduction from the proposed fenceline monitoring and did not account for any of the potential costs associated with achieving such emission reductions ( i.e., the EPA only considered the costs of the actual monitoring and not the root cause and corrective action requirements). A commenter asserted that had the EPA appropriately accounted for costs, it would have concluded that the proposed fenceline monitoring requirements are not cost-effective, consistent with the Agency's determination for the options considered for equipment leaks, PRDs, and storage vessel breathing losses. The commenter argued that the EPA failed to quantify the additional HAP emissions reductions for EtO and chloroprene that the Agency indicates will be required for compliance or to consider the cost of these additional reductions (in addition to the cost of the required root cause and corrective action analyses) as is required to meet the Agency's obligation under CAA section 112(d)(2). The commenter stated that the EPA has not assigned emissions reductions of benzene, 1,3-butadiene, ethylene dichloride, or vinyl chloride as a result of implementing the proposed fenceline monitoring work practice requirements; and with the exception of EtO and chloroprene, the Agency implies that additional reductions beyond those the EPA proposed elsewhere in the rulemaking will be unnecessary to meet the fenceline action levels. The commenter attested that the EPA proposed additional requirements on top of those already required by the existing rules, or that will be required as part of the other proposed revisions ( e.g., the proposed flare standards, the existing and proposed monitoring requirements for process vents, and equipment leaks and PRDs), without identifying deficiencies in the current and proposed requirements. Similarly, other commenters stated that the EPA has not demonstrated that fenceline monitoring is necessary to reduce HAP emissions or to provide an ample margin of safety; and the lack of emissions reductions associated with the proposed requirements shows that such requirements are unnecessary to the ultimate goals of CAA section 112.

Response: We disagree with the commenters' assertion that the proposed fenceline monitoring work practice standard is not authorized under CAA section 112(d)(6), but we are making certain changes to the fenceline monitoring program in the final rule in response to comments, including adopting a second action level for just chloroprene under CAA section 112(f)(2). Contrary to the commenter's claims, we specifically proposed the fenceline monitoring standard under CAA section 112(d)(6) to be a work practice standard that is applied broadly to target fugitive emissions sources located at HON and P&R I facilities. The proposed standard does more than impose monitoring as some commenters suggested; it also limits emissions from sources because it requires the owner or operator to identify and reduce HAP emissions through a monitoring and repair program, as do many work practice standards authorized under CAA sections 112(h) and (d). We note that the sources addressed by the fenceline monitoring standard—fugitive emissions sources such as wastewater collection and treatment operations, equipment leaks, heat exchange systems and storage vessels—are already subject to work practice standards. Our review of these requirements indicates that this fenceline monitoring work practice standard would be a further improvement in the way fugitive emissions are managed and would, by providing such further assurance of compliance with emission standards and work practice standards, also provide an extra measure of protection for surrounding communities. Consistent with the criteria in CAA section 112(h)(2), we determined and established that work practice standards are appropriate for fugitive emissions at the time we established the initial MACT standards. Today, we reaffirm that it is impracticable to directly measure all fugitive emission sources at a given source but do not consider it necessary to reiterate these findings as part of this action to add the fenceline monitoring provisions for these sources under CAA sections 112(d)(6) and (f)(2). We note that the commenters do not provide any grounds to support a reevaluation as to whether these fugitive emission sources are appropriately regulated by a work practice standard.

The EPA, in establishing action levels for the fenceline monitoring work practice standard, relied on the authority provided in CAA section 112(d)(6) to set action levels at the highest concentration anticipated, considering the emission reductions anticipated under the additional standards we are adopting under CAA sections 112(d)(6) and 112(f)(2). Again, the section 112(d)(6)-based action levels function to verify the expected emissions reductions resulting from compliance with the final emission standards, and reflect concentration levels that are largely already resulting from sources subject to the rules and are therefore cost-effective. Further, in the proposal the EPA acknowledged that the proposed action levels for EtO and chloroprene of 0.2 ug/m³ and 0.3 ug/m³, respectively, were lower than the fenceline modeled concentrations for EtO and chloroprene from facilities in the SOCMI and Neoprene Production source categories after implementation of the proposed emission standards, and we took comment on whether we should require these lower action levels under CAA section 112(f)(2). In this final rule, we believe it is reasonable, given the unique circumstances presented by these source categories, to require these lower action levels. First, for EtO, the lower action level reflects concentrations that all HON-subject facilities, except for one, are currently meeting and are therefore cost-effective under CAA section 112(d)(6). Second, consistent with the second step of the risk review under the Benzene NESHAP approach addressing whole-facility risks, for chloroprene the lower action level reflects concentrations what will result in whole facility risks from this HAP dropping to 100-in-1 million. Further whole-facility reductions in EtO and chloroprene emissions from other sources located at major source facilities subject to these standards, including sources outside the source category, will help reduce risks from the whole-facility emissions of EtO and chloroprene from facilities with sources in the SOCMI and Neoprene Production source categories.

To reduce risk in the final rule we are making an adjustment from what was proposed. First, we are establishing under CAA section 112(d)(6), for all six of the monitored pollutants, action levels that correspond to the fenceline concentrations expected to result from compliance with the final rule's standards and work practices applicable to HON and P&R I processes and which reflect concentrations that HON and P&R I sources are largely already achieving, such that these action levels function to provide further assurance of such compliance of the emission standards and provide for corrective action when action levels are exceeded. For benzene, 1,3-butadiene, ethylene dichloride, EtO and vinyl chloride, these are the same action levels as proposed. For chloroprene, instead, the action level has been adjusted upward to 0.8 ug/m³ (see Docket Item No. EPA-HQ-OAR-2022-0730-0091, page 24) to reflect the modeled expected fenceline concentration resulting from the other final standards and work practices chloroprene. This first action level is, therefore, consistent with how we established fenceline monitoring requirements under CAA section 112(d)(6) in the petroleum refineries NESHAP and how we represent the primary CAA section 112(d)(6)-based fenceline monitoring program under the final rule.

Although the EtO action level of 0.2 ug/m³ is lower than what the EPA's modeling shows will result from compliance with the final CAA section 112(d) and 112(f) SOCMI source category emission standards in the final HON, as we discussed in the proposed rule, we expect that major sources with HON processes will be able to employ additional facility-wide measures, including those at other EtO-emitting processes outside of the SOCMI source category, to obtain additional cost-effective EtO reductions via improvements in maintenance and operations and enable compliance with the CAA section 112(d)(6) EtO action level. This is already being demonstrated by the fact that all HON-subject facilities, except for one, are already showing concentrations at or below the final action level. Moreover, this is reasonable due to the integrated nature of chemical plant operations, where multiple process units may be subject to NESHAP for more than one source category and products of units in some categories may also be feedstocks for units in other source categories. Accordingly, the source category designations, while part of the NESHAP program, are somewhat of an artificial distinction in these highly integrated chemical manufacturing facilities. For example, there are emission sources that often serve the entire facility, such as wastewater treatment systems and heat exchange systems, but they are typically assigned to a single source category or subcategory. Because of the propensity for large integrated chemical plants to contain numerous source categories, and also to contain units that span multiple source categories, we are finalizing fenceline work practice standards with an EtO action level that relies on achieving reductions across the whole HON facility, even if that includes non-HON EtO-emitting processes.

Second, in light of the very high risk presented by chloroprene emissions, we have concluded it is appropriate, in addition to adopting the primary CAA section 112(d)(6)-based action levels and monitoring program for all six subject HAP, to supplement the program with a secondary action level for this pollutant. This secondary action level, equivalent to that proposed, reflects fenceline concentrations for this pollutant that increase the margin of safety and advances the objectives of CAA section 112(f)(2). Although our modeling indicates that compliance with the other emission standards and work practices promulgated for Neoprene Production sources may not produce this secondary level, we anticipate—as explained in the proposal—that major sources will be able to employ additional facility-wide measures, such as maintenance measures, to achieve further chloroprene reductions to reach this secondary, CAA section 112(f)-based action level.

In the case of chloroprene emitted by the Denka Performance Elastomer, LLC facility (subject to both the P&R I NESHAP and the HON), we do not anticipate taking further source-category-wide rulemaking action that could re-set CAA section 112(d)(6)-based lower action levels to reflect future additional chloroprene reductions from additional source category processes. Consequently, for Denka Performance Elastomer, LLC's chloroprene emissions, this rulemaking is the final opportunity for us to establish an action level with the goal of assuring that whole-facility chloroprene emissions are reduced to a level that provides an ample margin of safety to protect public health. This is consistent with the statute because under the CAA section 112(f)(2) ample margin of safety second step, the Benzene NESHAP approach that is incorporated into the CAA allows the EPA to consider quantified or unquantified health effects, effects due to co-location of facilities, and co-emission of pollutants.

We disagree that the fenceline monitoring standards we are finalizing in this rule are redundant with MACT emissions standards for fugitive HAP emissions sources. The MACT standards impose requirements on fugitive HAP emissions sources consistent with the requirements in CAA section 112(d)(2) and (3), and the fenceline monitoring requirement is not a replacement for those requirements. Rather, based on our review of these standards, we concluded that the primary CAA section 112(d)(6)-based fenceline monitoring program is a development in practices, processes or control technologies that is a necessary revision to the previous standard, as it would improve management of fugitive emissions in a cost-effective manner and help assure compliance with applicable process emission standards under the HON and the P&R I NESHAP. Requiring sources to establish a fenceline monitoring program that identifies HAP emission sources that cause elevated pollutant concentrations at the fenceline, and correcting high emissions through a more focused effort, augments but does not replace the existing requirements. We found that, through early identification of significant fugitive HAP releases through fenceline monitoring, compliance with the Refinery MACT fenceline work practice standard for these similar emissions sources in these source categories has resulted in a significant reduction in benzene emissions. The action levels for the primary fenceline work practice standard, by contrast, are not based on the best performers but rather on the highest value expected on the fenceline from any source, based largely on the modeling of emission inventories expected to result from compliance with the final emission standards and work practices under the rules.

Lastly, we acknowledge commenters' support for fenceline monitoring. However, with respect to the commenter requesting that a third party be required to monitor the fenceline concentrations, the EPA disagrees. Fenceline monitoring requires a level of access to the facility and measurement devices that would be burdensome to accommodate for facilities. Fenceline monitoring is intended to address concerns with underreported emission inventories and works based on timely root cause analysis. Adding a third-party requirement would slow a facility's ability to respond to fugitive emissions in a timely manner.

Comment: A commenter argued that fenceline monitoring is not an emissions standard or work practice within the meaning of CAA section 112. Citing CAA section 302(k), the commenter said that, by itself, fenceline monitoring does not reduce emissions, rather all that fenceline monitoring does is identify ambient concentrations of a specific chemical; it does not even identify whether the chemical is from a regulated source, let alone identify a specific regulated unit at such source. The commenter said that fenceline monitoring can only potentially reduce emissions when coupled with additional requirements, but, at least in this instance, the EPA does not appear to claim associated reductions from the source category. The commenter added that while the EPA is proposing “action levels,” again, these levels alone do not “limit the quantity, rate, or concentration of emissions.” The commenter said that according to the preamble, if the emissions inventories are accurate, “all facilities should be able to meet the fenceline concentration action levels considering the controls [EPA is] proposing”; therefore, even when coupled with action levels, the EPA's proposal does not claim that fenceline monitoring will result in any meaningful emissions reductions from the source category. The commenter also stated that while exceedance of an action level may trigger further requirements, the action level does not, by itself or combined with fenceline monitoring, limit emissions—additional actions are required; and, because the EPA's proposal measures ambient concentrations, an exceedance of a proposed action level is not necessarily the result of emissions from the facility in question or from an exceedance of a standard.

The commenter noted that while the EPA states that it is proposing fenceline monitoring as a work practice standard, which could fall within the meaning of “any design, equipment, work practice or operational standard promulgated under [the CAA],” the EPA does not explain how fenceline monitoring meets the requirements for a work practice standard. The commenter added that work practice standards are authorized only in limited circumstances under CAA section 112(h)(1) when it is not feasible to prescribe or enforce an emission standard for control of HAPs, and the EPA has not adequately explained what elements of the proposal are work practice standards.

Response: Section 112(d)(6) of the CAA requires the EPA to review and revise the MACT standards, as necessary, taking into account developments in “practices, processes and control technologies.” Consistent with our long standing practice for the technology review of MACT standards, in section II.G.1 of the proposal preamble, we list five types of “developments” we consider.

Fenceline monitoring fits squarely within two of those five types of developments (emphasis added):

• Any add-on control technology orother equipment that was not identified and considered during development of the original MACT standards.
• Anywork practice or operational procedure that was not identified or considered during development of the original MACT standards.

As used here, “other equipment” is clearly separate from and in addition to “add-on control” technology and is broad enough to include monitoring equipment. In this case, fenceline monitoring includes equipment that we did not identify and consider during development of the original MACT standards. Additionally, the primary fenceline standard is a work practice standard, involving monitoring, root cause analysis, and corrective action not identified at the time of the original MACT standards. Therefore, the primary fenceline requirements are a development in practices that will improve how facilities manage fugitive emissions, and the EPA appropriately relied on CAA section 112(d)(6) in requiring this standard. (Note: The EPA is not relying on CAA section 112(f)(2) as the basis for the primary fenceline monitoring work practice standard established under section 112(d)(6) for benzene, butadiene, vinyl chloride, ethylene dichloride, chloroprene, and EtO, and has set action levels according to the annual average concentrations modeled at the facility fenceline for any facility after compliance with process unit emission standards applicable to HON and P&R I sources and that reflect levels sources are largely already achieving. However, as discussed elsewhere in this section of the preamble, we are also setting a secondary action level of 0.3 ug/m³ for chloroprene under CAA section 112(f)(2), because this standard will further reduce risks from the whole-facilities consistent with the goal to provide an ample margin of safety to protect public health).

Comment: A commenter argued that the EPA's explanation for the basis of selecting the six compounds for fenceline monitoring is inadequate when compared against the rulemaking record. The commenter said that the EPA appears to base its selection of compounds on previous and current risk drivers because the EPA indicates that “[s]everal of these compounds were identified as cancer risk drivers in the prior risk and technology reviews for the HON and P&R I NESHAP conducted in 2006 (HON) and 2008 and 2011 (P&R I). . ..” The commenter contended that, with the exception of EtO, the maximum risk previously found by the EPA in its reviews for the HON and P&R I NESHAP were well below 100-in-1 million (or not identified as a risk driver at all); the commenter provided a table showing the EPA's determinations of 2006 HON, 2008 P&R I and 2011 P&R I MIR for benzene, 1,3-butadiene, chloroprene, EtO, ethylene dichloride, and vinyl chloride. The commenter pointed out that in each of these previous assessments, the EPA found risks acceptable and did not adopt additional standards to address residual risk or to ensure an ample margin of safety. The commenter said the EPA also did not identify benzene, 1,3-butadiene, ethylene dichloride, or vinyl chloride as driving unacceptable risk under the current assessment; thus, while the EPA's selection of benzene, 1,3-butadiene, ethylene dichloride, and vinyl chloride based on risk is questionable under the EPA's framing of the option as part of its CAA section 112(d)(6) technology review, a closer inspection of the EPA's previous risk assessments indicates that in fact, these compounds did not drive any unacceptable risk. The commenter stated that the EPA's proposal to require millions of dollars of monitoring for no emissions reductions is unjustified under CAA section 112(d)(6) and unnecessary under CAA section 112(f). The commenter added that they acknowledge that the EPA found EtO and chloroprene to be risk drivers as part of their voluntary assessment supporting this proposed rulemaking and are claiming unquantified emissions reductions as a result of implementing fenceline monitoring; however, according to the commenter, the Agency determined that these additional reductions are unnecessary under CAA section 112(f) when it proposed to find acceptable risk and an ample margin of safety after implementation of the controls detailed in section III.B.2.a of the proposal preamble (88 FR 25080, April 25, 2023).

The commenter argued that it would be inappropriate to consider fenceline monitoring in context of the CAA section 112(f) review. The commenter stated that the EPA has already concluded that the controls that it has proposed to impose protect human health and the environment with an ample margin of safety. The commenter added that the EPA has not identified any additional emission reductions from the source category that would be necessary to reduce risk from the source category and that the EPA has failed to demonstrate that any such controls are cost-effective, which would be included as any ample of safety analysis. The commenter also said that the action level is not tied in a meaningful way to reducing risk to an acceptable level.

Response: The EPA implemented a fenceline monitoring standard to address emissions of pollutants that it determined could cause unacceptable risk, based on risk modeling of emission inventories and accounting for the range of uncertainty associated with these estimates. When the EPA promulgated the Refinery MACT fenceline work practice standard, the EPA acknowledged that emissions of benzene and indeed, of all other HAP in the source category, did not pose unacceptable risk when emissions from refineries were modeled, but that the work practice standard was put in place to address the uncertainty associated with emission estimates from fugitive sources and to preserve the decisions regarding the findings of acceptable risk and ample margin of safety (79 FR 36290, June 30, 2014). The same uncertainty exists here for the SOCMI and P&R I source categories. As explained in the April 25, 2023 proposal, we collected fenceline measurements in addition to modeling inventories, and our fenceline measurements indicate that concentrations at the fenceline almost always exceed modeled concentrations, indicating the potential for significant uncertainty with regard to our risk analysis and findings of acceptable risk. As discussed earlier in this document, the EPA is not relying on CAA section 112(f)(2) as the basis for the primary fenceline monitoring work practice standard established under CAA section 112(d)(6) for benzene, butadiene, vinyl chloride, ethylene dichloride, chloroprene, and EtO and has set action levels according to the annual average concentrations modeled at the facility fenceline for any facility after compliance with process unit emission standards applicable to HON and P&R I sources and that are reflective of concentrations subject sources are already achieving. Further, we disagree with the commenters who suggest that the EPA may not require fenceline monitoring pursuant to CAA section 112(d)(6) because the EPA has not determined that fenceline monitoring is necessary to ensure an acceptable level of risk or to provide an ample margin of safety. CAA section 112(d)(6) does not require the EPA to factor in the health considerations provided in CAA section 112(f)(2) when making a determination whether it is “necessary” to revise the previous emission standard.

For chloroprene, we are finalizing in the primary CAA section 112(d)(6)-based program the action level of 0.8 ug/m³ that reflects compliance with the source category-specific emissions limits for the Neoprene Production source category in the P&R I NESHAP. Separately, we are also setting a secondary action level of 0.3 ug/m³ for chloroprene under CAA section 112(f)(2), because this standard further reduces from the whole-facility risk from sources emitting chloroprene to levels that are consistent with the goals of CAA section 112(f)(2). As discussed earlier, in the proposal, we acknowledged that the proposed action level of 0.3 ug/m³ for chloroprene is lower than the fenceline modeled concentrations from facilities in the Neoprene Production source category after implementation of our proposed standards under CAA section 112(f)(2); however, considering whole-facility risks, and in light of the configuration of the emission sources subject to these rules that contribute to whole-facility risk that remain for the impacted communities after the imposition of controls, we are setting the additional second action level for chloroprene at facility boundaries as low as possible (considering method detection limitations) to ensure that the emission reductions anticipated from implementation of controls used to meet the proposed standards and to achieve additional chloroprene emission reductions are achievable. Reductions to achieve this action level will likely come from controlling additional emission sources at the one Neoprene Production facility that might not be considered part of the source category. Controlling these sources reduces emissions from the entire facility, not just the source category, and makes it possible for operators to achieve the lower action level. Thus, in this final rule, and based on the unique circumstances presented here, we consider facility-wide risk as an additional factor we may consider under CAA section 112(f)(2) and, in addition to the primary CAA section 112(d)(6)-based fenceline monitoring program addressing all six subject HAP, we are promulgating a separate and secondary lower action levels for just chloroprene under CAA section 112(f)(2).

Comment: Many commenters requested that the EPA expand the fenceline monitoring requirements to every facility in the SOCMI, P&R I, and P&R II source categories so owners and operators of these facilities can demonstrate, by representative monitoring data, that pollution from these facilities poses minimal levels of harm to fenceline communities. Some of these commenters pointed out that, as proposed, only about 60 percent of the facilities in these source categories would have to conduct fenceline monitoring. Other commenters contended that, as proposed, 90 facilities would have no fenceline monitoring requirements. A commenter contended that there is no reason or need for the EPA to have selected just six toxic pollutants and used them as basis to omit facilities from fenceline monitoring, given that CAA section 112(d)(6) requires making any changes that are “necessary” to bring standards into full compliance with the CAA, such as setting limits on uncontrolled and inadequately controlled emissions. The commenter pointed out that the EPA set fenceline monitoring requirements that applied to all refineries subject to NESHAP subpart CC and did not omit sources based on the selected constituents to be monitored.

Some commenters suggested that the EPA could add more toxic pollutants to its current list of six fenceline monitoring constituents, in order to ensure that each facility has at least one or more sentinel chemicals that can be monitored. A commenter recommended that the EPA include benzene, toluene, ethylbenzene, and xylenes (BTEX), methanol, and formaldehyde constituents to the list of pollutants requiring fenceline monitoring. The commenter pointed out that based on TRI data, the inclusion of formaldehyde to the list of pollutants requiring fenceline monitoring would add another 28 facilities, the inclusion of methanol would add another 13 facilities, and the inclusion of BTEX/n-hexane would add another 3 facilities. The commenter also pointed out that it is no surprise that information gathered from only HON and P&R I sources resulted in constituents most representative of those sources and not representative of P&R II sources; and had the EPA included P&R II data in the information it gathered for the purpose of fenceline monitoring constituents, the EPA would have found that all five P&R II sources emit epichlorohydrin and that several of them emit the non-benzene BTEX constituents. Commenters requested that the EPA add formaldehyde to the list of pollutants requiring fenceline monitoring because the IRIS data indicates that as a carcinogen, formaldehyde is even more potent than benzene. A commenter said evidence from emission reports suggests that some facilities may be underreporting or only sporadically reporting formaldehyde emissions ( e.g., the Conoco-Phillips/Shell Wood River manufacturing site in Illinois reported very large formaldehyde emissions to the NEI in 2017 and even larger amounts to the 2020 NEI but has not disclosed formaldehyde emissions in any of the TRI reports for the facility for the 5 years between 2017 and 2020). A commenter recommended that the EPA require each facility to select the constituents to be monitored via tailored fenceline monitoring plans that are specific to each facility's emissions and risk drivers. Additionally, at least one commenter said they hope that EPA will replicate this multi-pollutant monitoring in other rules, including as a supplement to the ethylene production rules.

On the contrary, some commenters argued that the proposed fenceline monitoring requirements would impermissibly regulate emissions from non-HON sources. Citing the proposal at 88 FR 25145-46, some of these commenters pointed out that the EPA expressly notes that facilities are not permitted to exclude non-HON sources of the target pollutants that are within facility property boundaries when determining whether monitored concentrations exceed action levels. The commenters said that regulating emissions from sources outside of the source category is incompatible with the EPA's statutory mandate to “review and revise” the “emissions standards promulgated under this section,” which refers to the source-category MACT standards promulgated under CAA section 112(d). The commenters stated that the EPA may only regulate HON sources under its technology review authority in accordance with the statutory language and structure of the CAA. The commenters reiterated that when enacting CAA section 112, Congress instructed the EPA to promulgate a list of specific source categories and that Congress then instructed the EPA to establish emission standards “[f]or the categories and subcategories the Administrator lists under subsection (d)” of CAA section 112. At least one of these commenters cited CAA sections 112(c), (d)(1), (d)(3)(A), (d)(6), and (f) as examples of how the CAA authorizes the EPA to impose emissions standards only on particular source categories or subcategories. The commenter asserted that none of these provisions expressly authorize or reasonably can be construed to allow the EPA to develop and impose an emissions standard that applies across multiple source categories. The commenter contended that for this reason, the EPA's proposal to apply fenceline monitoring to site-wide emissions, including emissions from source categories beyond the SOCMI source categories addressed in this rulemaking, is legally unfounded; and if the EPA decides to impose a fenceline monitoring program in the final rule, it must be limited such that it applies only to emissions from particular source categories. Other commenters said they were concerned that the proposed approach results in the EPA's establishing the emission point as the facility boundary, thereby expanding the definition of an affected source. The commenters provided an example saying that the proposed rule does not contain provisions that would exclude a site from fenceline monitoring for benzene due to the presence of a gasoline storage tank onsite that is used to refuel mobile equipment and is not even part of the HON process.

Some of the commenters stated that the imposition of fenceline monitoring requirements to non-HON sources is unreasonable, arbitrary, and capricious. One of these commenters said the EPA is conducting the technology review for the SOCMI category and not for other collocated categories; and despite this, the EPA is using this action as a vehicle to impose requirements on other source categories through the HON rather than evaluating such controls in the context of the applicable CAA section 112 standard. The commenter asserted that such use of a source-specific technology review to promulgate requirements that affect an unknown number of other source categories is arbitrary and capricious and circumvents statutory design. The commenter added that the EPA has not assessed the cost that would fall on other source categories and that the EPA's proposal failed to properly provide notice or provide a meaningful opportunity to comment to all interested stakeholders.

Some commenters said that they support the EPA's proposal to allow facilities to account for offsite, upwind sources through the use of near-field source correction under 40 CFR 63.184(g); however, these commenters said they disagree with the EPA's assertion that this option should not be provided for onsite, non-source category emissions. These commenters asserted that the EPA cannot regulate sources beyond those subject to the technology review; thus, the commenters said, the EPA should add provisions in the final rule similar to those at 40 CFR 63.658(i) from the 2015 Petroleum Refinery Sector Rule to address onsite sources that are not part of the affected source under the HON and P&R I NESHAP. However, at least one commenter objected to adding provisions in the final rule similar to those at 40 CFR 63.658(i) and stated that inclusion of facility-wide emissions in the action level is appropriate because it will support the control of toxic air pollutants emitted from all sources within the facility, all of which affect fenceline communities, and also avoids the development of complex and uncertain processes to attribute emissions from collocated sources and equipment that may be used in processes associated with multiple source categories. This commenter pointed out that only a small number of refineries (13) have approved site-specific monitoring plans, and only five of those plans include procedures for excluding onsite sources owned by the refinery but that do not fall within the refinery source category.

Another commenter provided a real-life example of the difficulty of dealing with onsite, non-source category emissions where Facility A, which is subject to the HON, owns and operates an Industrial Site that supplies services to other tenants, including wastewater treatment. The commenter said that Facility A does not use, produce, or emit EtO from any of its own processes; however, two tenants—Facility B and Facility C—are located inside the Industrial Site, and both emit EtO (and Facilities B and C are not subject to the HON but are subject to 40 CFR 63, subpart PPP). The commenter said that Facilities B and C send miniscule liquid EtO emissions to the WWTP for disposal; and reported emissions by Facility A of EtO from their WWTP, since taking over the Industrial Site, are less than 1 lb/yr. Using this example, the commenter contested that it is inappropriate to require Facility A to perform EtO fenceline monitoring and conduct a root cause analysis with subsequent corrective action because Facility A does not use, store, or emit EtO from any of their own production processes ( i.e., Facility A only has EtO wastewater emissions from treating EtO wastewater from Facility B and Facility C as the site owner). The commenter made the following additional points: (1) The amount of EtO emitted to the air from wastewater obtained and treated by other facilities from Facility A has been less than a pound for the past 3 years; (2) the WWTP is located outside the fenceline of the Industrial Site; (3) Facility A does not have the authority to perform root cause analysis or corrective actions on facilities they do not have operational control over; and (4) if action level concentrations are found, it is not possible to determine whether the EtO comes from Facility B and/or Facility C, nor their individual contributions. For the Facility A WWTP, there is not a logical corrective action for emissions of less than 1 lb/yr that would change the EtO concentrations found in the ambient air. Other commenters provided similar examples and expressed similar concerns.

Response: The EPA considered the potential applicability of fenceline monitoring as part of this proposed technology review. Generally, the EPA has found fenceline monitoring to be an effective tool when fugitive or ground-level releases are significant or where we have identified considerable uncertainties in HAP emissions estimates from fugitive emission sources such that they affect our decisions relative to whether there exists residual risk, for example. Other considerations include the types of pollutants that are emitted, the availability of fenceline monitoring measurement methods for the key pollutants, proximity of residences or other areas where people could be exposed to emissions at or near facility fencelines, and the other types of monitoring that are already required or are being considered.

Regarding the question of including onsite, non-source category emissions in the fenceline monitoring work practice standard, we proposed not to allow corrections to monitoring for onsite non-source category sources, as they were included in emissions sources modeled to develop the action levels. In other words, the action levels in the primary fenceline monitoring program are based on expected facility-wide emissions and account for contributions from these non-source category sources. For more details, see the document titled Clean Air Act Section 112(d)(6) Technology Review for Fenceline Monitoring located in the SOCMI Source Category that are Associated with Processes Subject to HON and for Fenceline Monitoring that are Associated with Processes Subject to Group I Polymers and Resins NESHAP (Docket Item No. EPA-HQ-OAR-2022-0730-0091) and the residual risk technical support document titled Residual Risk Assessment for the SOCMI Source Category in Support of the 2023 Risk and Technology Review Proposed Rule (Docket Item No. EPA-HQ-OAR-2022-0730-0085). The secondary action level for chloroprene adopted under CAA section 112(f)(2) appropriately anticipates the need for additional reductions of this pollutant in order to further the goal to protect public health from whole-facility chloroprene emissions. Further, in most cases, sources with HON or P&R I source categories also account for a significant portion of the action level at the fenceline such that the option to attribute and correct monitors for emissions from collocated sources and equipment that may be used in processes associated with multiple source categories becomes a very complex and unnecessary process. In the Petroleum Refinery example, we note that the option to correct monitors for non-source category sources within the fenceline was found to be very difficult to implement practically and that the option was subsequently removed from most site-specific monitoring plans.

We agree that the circumstance described by the commenter, although uncommon, might result in a situation where the most significant contribution would not be from the portions of the facility that are subject to the process limits established for the HON or P&R I source itself. In this case we would apply the requirements based on how the source has been defined for the purposes of applicability of CAA section 112 standards, which is any stationary source or group of stationary sources located within a contiguous area and under common control. The commenter indicates that these facilities are not under common control, therefore Facility A would have to conduct fenceline monitoring because it does use, produce, and emit EtO, and it is subject to the HON, as the commenter indicates that it treats wastewater from Facilities B and C in its wastewater treatment process. In this case, Facility A could correct monitoring readings for offsite impacts using a site-specific monitoring plan. Depending on the orientation of Facilities B and C, this approach would require real-time monitoring of portions of the fenceline bordering Facilities B and/or C and is allowed by the proposed and final rule (see 40 CFR 63.184(g)). The commenter presumes that the amount of EtO emitted by the treatment process is miniscule, but that is precisely the question that fenceline monitoring is envisioned to address and to ensure that emissions are maintained at low levels. We believe even in this situation, the fenceline monitoring standard is reasonable and provides for an approach to address the commenter's concerns. Further, we reject the notion that our proposal failed to properly provide notice or to provide a meaningful opportunity to comment for all interested stakeholders. The major source to which these standards apply is by definition under common control. Unless the sources are subject to the HON and P&R I standards, there is no requirement for operators of other source categories to comply with these requirements. Therefore, we reject the notion that this proposal is arbitrary and capricious and circumvents statutory design.

Comment: With regard to the EPA's proposed fenceline monitoring requirements, numerous commenters contended that background concentrations need to be accounted for when calculating the incremental contributions from EtO-emitting facilities. A commenter said that without understanding the significance of high ambient background levels, it is not possible to determine a facility's true impact on ambient concentrations above the background level or the risk of EtO exposure. This commenter added that implementation of fenceline monitoring when background is unknown has the potential to generate data that will not represent what is intended, will require follow up action to correct problems that do not exist, and has the potential to frighten communities near facilities in the absence of elevated risk. Similarly, other commenters asserted that facilities are likely to show exceedances attributable not only to their own emissions, but also from background levels of EtO and emissions of EtO sources from offsite sources. These commenters said that background concentrations threaten a potentially endless cycle of investigations for the source of emissions which are beyond the EPA's regulatory authority or the facility's control; and the proposed fenceline monitoring requirements improperly attempt to turn facilities into mini ambient air quality regulators, requiring them to investigate and analyze fenceline exceedances that could be caused by another facility, background EtO levels, or simply an error in sampling due to the inability to accurately measure EtO at the incredibly low levels proposed.

Some of these commenters acknowledged that the EPA's proposed sampling protocol attempts to address background concentrations by taking the highest sample and subtracting the lowest sample from it; however, these commenters said it is not clear how the proposed protocol fully addresses background concentrations and other questions that remain regarding high background concentrations that have been present in sampling conducted by other states, including at National Air Toxic Trends Station (NATTS) sites. These commenters as well as others said that background monitors in many cases show higher concentrations than monitors located within or nearby EtO-emitting facilities. Some of these commenters provided additional information about background EtO concentration data available from two studies conducted by state agencies:

• A 2022 study conducted by the Georgia Department of Natural Resources, Environmental Protection Division titled “Ethylene Oxide Monitoring Report” included EtO monitors near known emitters in addition to areas designated as “background” locations away from any known emitters of EtO. The 2020 concentration data for one of the background monitors located in South DeKalb showed that background concentrations ranged from a low of 0.10 μg/m³ to a high of 3.7 μg/m³ and that the monthly difference between the highest and lowest reported concentration value ranged from 0.22 μg/m³ to 3.2 μg/m³, with an average monthly difference of 0.88 μg/m³.
• A 2022 study conducted by the West Virginia Department of Environmental Protection in the Kanawha Valley, collecting background concentration data in Guthrie and Buffalo, West Virginia, revealed that EtO background measurements were made in Guthrie that ranged from 0.059 μg/m³ to 1.74 μg/m3 and in Buffalo that ranged from 0.20 µg/m³ to 1.31 µg/m³.

Commenters claimed that the reports published by the Georgia Department of Natural Resources, Environmental Protection Division, and by the West Virginia Department of Environmental Protection indicate that background concentrations of EtO can vary significantly, including up to more than an order of magnitude greater than EPA's proposed action level of 0.20 μg/m³. Other commenters noted that the EPA's AirToxScreen presents EtO background levels as zero (so risks associated with background levels of EtO are not included in AirToxScreen maps and reports); however, according to commenters, this is highly unlikely to be the case, as shown by data in the EPA's NATTS sites, which are designed to be representative of community air toxics concentrations. Another commenter cited the West Virginia final report titled “Ethylene Oxide Monitoring—Characterization of South Charleston and Institute, West Virginia and Surrounding Areas February 21, 2023” and made the following observations of the measured EtO background concentrations from year 2018 through November 2021 at various monitoring points across the United States:

• There is not even a single data point below the EPA's 100-in-1 million threshold of 0.01 parts per billion by volume (ppbv).
• The average concentration is 0.122 ppbv which is 12 times higher than the EPA's 100-in-1 million threshold of 0.01 ppbv.
• Several monitoring sites have an annual average concentration of 0.15 ppbv (0.27 ug/m³ or higher).
• Many of these values are measured at sites that are not close to industrial sites where EtO is manufactured or used, thus further calling into question whether the EPA really has the correct residual risk value.

Citing the EPA produced document titled “EPA's Work to Understand Background Levels of Ethylene Oxide” (most recently updated in October 2021), another commenter presented the following questions that they claimed to be unanswered: (1) Is EtO in use by unpermitted sites that are causing these levels?; (2) is EtO coming from other activities/sources such as mobile sources, biogenic sources?; and (3) when the IRIS inhalation URE value was developed, did the analysis include consideration of the background dosing?

Response: We disagree with the commenters' assertions that background concentrations of EtO are not accounted for in the proposed fenceline monitoring provisions. The primary driving force for determining when a facility must initiate root cause analysis is the annual average Δc value; a root cause analysis is required whenever the annual average Δc value is higher than the action level. For EtO, the annual average Δc is the average of the most recent 73 individual sampling period Δc measurements. The sampling period Δc is calculated as the sampling period's highest sample result minus the sampling period's lowest sample result. If background EtO levels are persistent in the area, this will be captured by both the high and low concentration measurements used to develop the Δc values and the subtraction will result in only the facility's contributions to the EtO concentrations at the fenceline. As such, background levels are accounted for in the determination of each sampling period's Δc value, and subsequently the annual average Δc value.

If, as commenters indicate, background EtO levels are inconsistent, the annual average Δc value must still shift above the action level before root cause analysis must be performed. The power of a single Δc value to cause undue root cause analysis is mitigated when it is averaged with the other measurements. Single events where background EtO levels are elevated will be insufficient to cause the annual average Δc to exceed the action level. If a single Δc value is large enough to skew the annual average derived from 72 other datapoints above the action level, the EPA expects that an emission event occurred and root cause analysis is appropriate.

Lastly, with respect to commenters' concerns that offsite facilities may contribute to EtO measurements at their facility, we note that owners and operators may submit site-specific monitoring plans to subtract background EtO concentrations from upwind emitters from impacted monitors pursuant to 40 CFR 63.184(g)(1) through (4).

The questions posed by the commenter about unpermitted sites emitting EtO or whether unknown sources are developing EtO are out of scope for this rulemaking. Section IV.A.3.a of this preamble addresses the EtO IRIS URE value.

Comment: Several commenters requested that the EPA clarify that very small amounts of the six compounds ( i.e., benzene, 1,3-butadiene, chloroprene, ethylene dichloride, EtO, and vinyl chloride) that may be produced, used, or stored at trace levels, as incidental by-products, and as impurities, should not trigger long-term fenceline monitoring requirements. Some of these commenters contended that the proposed applicability is unjustifiably broad, rendering it arbitrary and capricious. The commenters requested that the EPA provide a de minimis level that would trigger fenceline monitoring requirements; and several of the commenters also requested that the applicability be limited to regulated HON CMPUs. Some of the commenters requested that the EPA create exclusions for predetermined de minimis activities such as: housekeeping or building maintenance, lab and research activities, combustion emissions, transportation emissions, and incidental by-products or impurities. Similarly, a commenter asserted that the EPA uses the phrase “use, emit, or process” without any other criteria or definition of what this language means.

A commenter pointed out that according to the EPA's AP-42 Compilation of Air Emission Factors, the combustion of fuels is likely to generate emissions of benzene and 1,3-butadiene (see AP-42, Tables 1.3-9, 1.4-3, 3.1-3, 3.3-2, and 3.4-3). The commenter added that since nearly all HON and NSPS III/NNN/RRR sources are expected to contain natural gas piping, and natural gas contains benzene, and the applicability of the fenceline monitoring requirement is based on site emissions, it is reasonable to conclude that nearly all HON and NSPS III/NNN/RRR sites are expected to be subject to the fenceline monitoring requirement regardless of whether the SOCMI processes at the site emit benzene or 1,3-butadiene. Another commenter said that implementing a fenceline monitoring program for any by-product/impurity that is intentionally minimized by the owner or operator is not cost-effective or environmentally beneficial, and as such, warrants additional consideration. The commenter stated that chloroprene is a by-product/impurity produced in their vinyl chloride monomer production process and would be emitted at much lower quantities than ethylene dichloride or vinyl chloride; and as described in the HON RTR Proposal, if the purpose of the fenceline program is to determine equipment leaks, the leaks would be more readily detected with vinyl chloride monomer or ethylene dichloride rather than through monitoring for a contaminant that may or may not be present in the process fluid.

Commenters suggested that to avoid trace levels of these compounds triggering the monitoring programs, the EPA should establish additional applicability criteria for triggering the monitoring requirements given that the proposed fenceline air monitoring provisions are complex, take significant time to implement, and appear to be required for an infinite period. The commenters said the economic burden for fenceline monitoring is not justified for facilities with low levels of emissions (below de minimis thresholds) for any proposed fenceline compound. Some of these commenters recommended that the EPA clarify that when the EPA uses the phrase “if the site uses, produces, stores, or emits” one of the covered chemicals, this means that greater than 25,000 lb/yr of a chemical must be used, produced, or stored in HON CMPUs at the source. Commenters added that in order to trigger fenceline monitoring, the air emissions for a covered chemical should also be greater than 1 tpy (~ 0.23 lb/hr annual average) from HON CMPUs at the source. Commenters said that the rationale for using 25,000 lb/yr aligns with other EPA regulations such as 40 CFR 372.25(a) which is threshold for reporting of air emissions under the EPA's Superfund Amendments and Reauthorization Act Section 313 program; and a 1 tpy emission threshold (<0.25 lb/hr) is a low threshold for then triggering the fenceline air monitoring program. Another commenter said that, given that the Agency selected the fenceline action levels by modeling emissions from the post-control emissions file in the residual risk assessment and selecting the maximum annual average fenceline concentration, one potential option for adopting a trigger threshold for fenceline monitoring would be to set emission thresholds at 50 percent of the source category emissions for the facilities that were used to set the proposed action level. The commenter said that this approach should also be applied for EtO and chloroprene because the Agency proposed to find acceptable risk and an ample margin of safety for these pollutants after implementation of the controls, thus making additional reductions of EtO and chloroprene unnecessary and unsupported by any rulemaking authority.

A commenter suggested that if the EPA does not establish de minimis applicability thresholds, then the final rule should include a provision that allows for fenceline monitoring to be discontinued at a site after 2 years of non-detect fenceline monitoring concentrations for a compound. The commenter said that a site with non-detect fenceline concentrations does not drive the risk assessment for that compound.

Response: The EPA disagrees with commenters that the fenceline monitoring provisions are unjustly broad. Per 40 CFR 63.184, the fenceline monitoring provisions are applicable “for each source as defined in § 63.101, and for each source as defined in § 63.191.” The definitions of source at 40 CFR 63.101 and 40 CFR 63.191 point to 40 CFR 63.100 and 40 CFR 63.190, respectively, where applicability is stated. For the HON, only those sources manufacturing as a primary product one or more of the chemicals in Table 1 to NESHAP subpart F, or tetrahydrobenzaldehyde, or crotonaldehyde; or using as a reactant or manufacturing as a product, or co-product, one or more of the HAP listed in Table 2 to NESHAP subpart F are subject to the provisions. For NESHAP subpart I, only those emissions specified from the processes subject to 40 CFR 63.190(b)(1) through (6) are subject to the fenceline provisions. Therefore, any concerns about obligations to meet fenceline monitoring requirements for pollutants developed as impurities or found in feedstock in trace amounts are unfounded, as these materials are not “products,” which, by definition, exclude by-products, isolated intermediates, impurities, wastes, and trace contaminants per the definition at 40 CFR 63.101 or, in the case of NESHAP subpart I, are not the specified pollutants from the processes to which the subpart applies. For P&R I sources subject to NESHAP subpart U, we note that the fenceline monitoring requirements reference 40 CFR 63.101 and the same logic can be applied.

To the commenter's assertion about emissions from boilers, housekeeping, building maintenance, or lab and research activities triggering fenceline monitoring requirements, we note that these are not considered within SOCMI or P&R I sources per the applicability of the term at 40 CFR 63.100. Thus, there would be no need to implement fenceline monitoring if these are the only sources emitting benzene, 1,3 butadiene, ethylene dichloride, vinyl chloride, EtO, or chloroprene at a facility. Therefore, for the reasons previously stated, there is no need to set a minimum threshold for fenceline monitoring as the rule already provides criteria targeting only SOCMI or P&R I sources using, producing, storing, or emitting one or more of the six considered pollutants and will not be triggered by low-level emissions from non-source category processes.

However, we agree with the commenter that the proposed language could be interpreted such that emissions from non-HON or P&R I processes could trigger the fenceline monitoring requirement. As such, we are revising 40 CFR 63.184(a)(1)(i) through (iv) and 40 CFR 63.184(b)(1)(i) and (ii) to state that owners and operators with an affected source that uses, produces, stores, or emits one or more of the target analytes must conduct fenceline monitoring for the analyte(s) at their site. At proposal, we inadvertently used the word site in these sections instead of affected source, which may have led to confusion that non-HON or P&R I processes could have triggered fenceline monitoring obligations when there were no HON or P&R I processes at the site that use, produce, store, or emit benzene, 1,3 butadiene, ethylene dichloride, vinyl chloride, EtO, or chloroprene. We believe this change clarifies our original intent and helps to more clearly target those facilities that were identified as needing fenceline monitoring as part of our original analysis (see Docket Item No. EPA-HQ-OAR-2022-0730-0091).

To address concerns with facilities producing, using, storing, or emitting only low levels of benzene, 1,3-butadiene, ethylene dichloride, or vinyl chloride, we are finalizing burden reduction measures at 40 CFR 63.184(a)(3)(iii) and (b)(2)(iii). These provisions, similar to those provided at 40 CFR 63.658(e)(3) of NESHAP subpart CC for benzene, will allow facilities to skip fenceline measurement periods for specific monitors once a certain number of fenceline measurements are recorded to be one tenth or less than the finalized action levels. We believe the addition of these provisions will unify the finalized fenceline monitoring provisions between NESHAP subpart H and NESHAP subpart CC so that collocated refinery processes will not become subject to additional monitoring if they have already demonstrated levels of benzene at the fenceline that allow the owner or operator to qualify for a reduced sampling frequency and support facilities producing, using, storing, or emitting only low levels of the targeted pollutants from their affected sources. We note that these provisions are not being provided for EtO and chloroprene due to their associated risk and the finalized secondary actions levels having been set at three times the representative detection limit (RDL), and thus demonstrating sufficiently low fenceline concentrations to allow skipping monitoring periods is not possible. Additionally, for both EtO and chloroprene, even for the primary action levels, one-tenth of the action level would be below the method detection limit (MDL), and as such, skipping monitoring periods would not be possible for these pollutants. We also note that for vinyl chloride, this option is limited to small sites with perimeters less than or equal to 5,000 meters. We have chosen to limit the reduced sampling frequency to these smaller sites because these are the only sites where the canister samples are taken at the same sampling location each sampling period; owners and operators of sites with a perimeter larger than 5,000 meters are required to rotate the sampling locations between sampling periods. As such, this complicates the determination as to whether a larger site has consistently low fenceline readings at a particular monitoring location.

Comment: A commenter pointed out that when fenceline monitoring was established for refineries, the EPA stated that benzene was specifically chosen as the target analyte for petroleum refineries with the understanding that a single HAP served as a surrogate for all fugitive HAP, further stating that a single HAP simplified the determination of compliance and set a clear action level. The commenter contested that it is unclear why benzene cannot be the surrogate for the species listed under the proposed EPA Method 325 fenceline monitoring requirements. Moreover, the commenter added that a site should only have to do the chlorinated species or EtO monitoring if it is present in sufficient quantities such that their emissions would create a concentration higher than MDL at the perimeter; the commenter asserted that the EPA set their action levels based on modeling of site emission inventories but did not incorporate any rationale for why sites with less emissions must do such expensive monitoring. The commenter suggested that sites should have the option to model or demonstrate that their emissions would not be expected to exceed the action levels without embarking on a costly monitoring program that will just be reporting below detection level values.

Response: Benzene was selected as a surrogate for all HAP as part of the fenceline monitoring provisions of NESHAP subpart CC due to its near universal presence in process streams. HON and P&R I processes are more diverse and there is no single chemical that is found with the same frequency in process streams as benzene in petroleum refineries. Setting one surrogate chemical to represent the variety of HON and P&R I processes considered as part of this rulemaking would not produce effective standards limiting fugitive emissions.

To the commenter's request to be able to model concentrations at the fenceline to show that action levels will not be met, we point to table 2 through table 7 in the document titled Clean Air Act Section 112(d)(6) Technology Review for Fenceline Monitoring located in the SOCMI Source Category that are Associated with Processes Subject to HON and for Fenceline Monitoring that are Associated with Processes Subject to Group I Polymers and Resins NESHAP (see Docket Item No. EPA-HQ-OAR-2022-0730-0091). Fugitive emissions are, by nature, difficult to measure and record and the data collected via the CAA section 114 request indicates that modeling is insufficient to anticipate fenceline concentrations of the six target pollutants considered. Therefore, we maintain that it is reasonable to require monitoring if a facility whose SOCMI or P&R I affected sources use, produce, store, or emit any of the pollutants specified at 40 CFR 63.184 to verify that actual concentrations at fenceline are below the finalized action levels. No changes are being made as a result of this comment.

Comment: Commenters said that they have concerns regarding equipment and lab analytical capabilities on whether any laboratory is capable of performing proposed EPA Method 327. The commenters asserted that they were only able to identify one lab in North America that could meet all requirements of proposed EPA Method 327. A commenter suggested that to the extent that fenceline monitoring for EtO is required, the EPA should allow for the use of EPA Method TO 15 for initial monitoring for at least one (1) year until lab capabilities are further established; or alternatively, the initiation of fenceline monitoring be moved to at least two (2) years after the effective date of the final rule. Another commenter encouraged the EPA to actively engage in dialogue with commercial air laboratories in the method review process to ensure that the procedures meet the EPA's quality objectives of the program and also can be supported on a production scale, both of which will be critical for the successful implementation of the canister fenceline monitoring network. Another commenter requested that the EPA provide a list of laboratories able to perform proposed EPA Method 327.

A commenter recommended that the EPA work with the New York State Department of Environmental Conservation (NYSDEC) to improve proposed EPA Method 327 given that NYSDEC analyzes VOCs in-house and has devoted considerable resources into refining its EtO measurement procedures over a seven year period. The commenter claimed that in a recent EPA performance audit of the NYSDEC laboratory required for NATTS sites, NYSDEC's EtO results were well within the 20 percent acceptability range and outperformed the referee laboratory. The commenter said proposed EPA Method 327 does not adequately address the issues that lead to inaccurate EtO measurements including, but are not limited to, the following:

• The preconcentration system must be optimized for the elimination of excess CO₂ and water.
• Slip-lining the transfer line in the gas chromatography (GC) oven with the analytical column to minimize contact between the concentrated slug and transfer line ensures that all or most of the transfer takes place directly onto the analytical column, which maximizes performance.
• Ion 44 should be used for quantitation. Use of ions 15 or 29 did not produce acceptable results in the NYSDEC laboratory. Ion 15 was too noisy and ion 29 suffered from interference due to background contributions from nitrogen. For NYSDEC, interference from trans 2-butene for ion 44 was not found to be an issue for normal ambient air samples due to the relatively low concentration of that substance in those samples. However, trans-2-butene can interfere with quantitation using ions 15 or 19, because, unlike ion 44, those are prominent masses in the mass spectrum of trans-2-butene.
• NYSDEC does not agree that bromofluorobenzene should be mandated as a tuning agent. NYSDEC has had success tuning prior to each run using perfluorotributylamine, per the manufacturer's recommendation, and has found that tuning to meet the bromofluorobenzene criteria can actually lower the sensitivity of the instrument.
• The use of internal standards for quantitation should not be mandated, especially for reactive chemicals like EtO and acrolein, as that procedure can produce biased results when the internal standard is not as sensitive to instrumental conditions as the target chemical. A better approach would be to use isotope dilution for the quantitation of these compounds, as the doped compounds would presumably react the same way in the analytical system. Given the anticipated very costly procurement of such internal standards, this should not be mandated, but instead suggested as a means to improve analytical performance for these reactive compounds. NYSDEC calibrates before, during, and after each analysis using the external standard approach and has complete confidence that the instrument is producing the best data within the confines of the system.

The commenter added that they strongly believe that any method refinements that enable more accurate EtO measurements should be implemented in all ambient sampling for that pollutant, including samples collected at NATTS sites, because this would allow for comparison of fenceline and background sites without methodological considerations.

Response: The EPA recognizes the commenters' concerns that laboratories may not currently have the capacity to conduct EPA Method 327 according to the timeline we proposed. Therefore, we are revising the final rulemaking at 40 CFR 63.100(k)(12) (for HON) and 40 CFR 63.481(p) (for the P&R I NESHAP) such that with the exception of fenceline monitoring of chloroprene at P&R I affected sources producing neoprene, owners and operators are not required to initiate fenceline monitoring until 2 years after the effective date of the final rulemaking. This expanded timeline is necessary to allow commercial labs to conduct the needed method development, to expand capacity, and to develop the logistics needed to meet the requirements in the final rule. For P&R I affected sources producing neoprene, we have changed the compliance date for fenceline monitoring of chloroprene to begin no later than October 15, 2024, or upon startup, whichever is later subject to the owner or operator seeking the EPA's authorization of an extension of up to 2 years from July 15, 2024. We note that that all affected sources producing neoprene (there is only one) already have a fenceline monitoring network in place for chloroprene as well as a lab contracted to provide analysis.

We developed EPA Method 327 based on the requirements in EPA Method TO-15A, best practices for measuring compounds like EtO, and enhanced QA/QC required for a method that is to be used for compliance purposes. Regarding the specific recommendations made by the commenter, the EPA has made EPA Method 327 as performance-based as possible and considers it important, when possible, to avoid prescriptive requirements to allow commercial laboratories to develop their own approaches for analysis.

Comment: Some commenters said that the EPA's proposed 300 parts per trillion (ppt) detection limit for EtO (and 900 ppt fenceline action threshold) are inadequate given that carcinogenic effects can be persistent and cumulative. These commenters claimed that EtO is toxic at 11 ppt in the ambient air; therefore, the EPA should mandate the use of advanced monitoring technologies to achieve lower detection limits and lower the action levels at the fenceline. A commenter remarked that in Louisiana, the typical residential location is not set at some safe distance from emissions; therefore, it is proper for the EPA to set minimum detection levels at the fenceline of the facility's property line, and not set the minimum detection level scalable to the duration of dispersion from the facility to the residential receptor location. Another commenter argued that developments in monitoring technology that lower the detection levels for listed HAP must be considered technological developments under CAA section 112(d)(6). This commenter contended that new technological developments, such as the use of proton transfer reaction-mass spectrometers and the use of Picarro products that use cavity ring-down spectrometers should be adopted by the EPA in its efforts to lower emissions in these source categories with the proposed fenceline monitoring efforts in the rules.

Another commenter declared that it is important to note that the method detection limit is nearly the same as the concentration that is representative of 100-in-1 million risk; therefore, any detection corresponds to an unacceptable level of risk. On the contrary, a commenter said that given ambient air measurements made using the EPA's TO-15/TO-15A summa canister method have a detection limit for EtO higher than 0.02 ug/m³, it is possible that the actual level could be above the EPA's 100-in-1 million risk level even if a regulated source or an agency were to obtain non-detect results. This commenter said that they are very concerned that the EPA has established ambient air targets that neither an industrial source nor a regulatory agency can demonstrate that they are meeting with current air sampling methods; this raises practical questions about how one demonstrates compliance with these air quality targets.

Response: The EPA recognizes the feedback from the commenters. We evaluated multiple measurement approaches that could be used for fenceline measurement, and there currently is not a measurement approach with reliable sensitivity at the level representative of 100-in-1 million cancer risk. The EPA found the only technically feasible approach to measure EtO at the fenceline is a canister measurement approach and analysis via gas chromatography/mass spectrometry (GC/MS). We developed EPA Method 327 based on the requirements in TO-15A, the EPA's existing canister method, Best Practices for measuring compounds like EtO, and enhanced QA/QC required for a method to be used for numerical compliance purposes.

We acknowledge the comment regarding real-time monitoring, and efforts are ongoing to evaluate different real-time monitoring approaches for EtO which could be applied to fenceline monitoring; however, we did not find these approaches to currently be technically or economically feasible. The EPA disagrees with the commenters that these real-time monitoring approaches are currently sensitive enough to currently be applied to fenceline monitoring; however, the EPA has a pathway for the use of these potential approaches through the alternative test method provisions in 40 CFR 63.7(f) when the required sensitivity is met, which is outlined in 40 CFR 63.184(i). We note that based on response to another comment, we are revising the entry for 40 CFR 63.7(f) in the General Provisions table to NESHAP subpart F (Table 3) such that 40 CFR 63.7(f) applies.

Comment: Many commenters expressed concerns that the proposed provisions for an alternative test method at 40 CFR 63.184(i)(3) require the method detection limit of the alternative method to be at least an order of magnitude ( i.e., ten-fold) below the action level for the compound(s) that will be monitored. A commenter indicated the proposed action level of 0.2 ug/m³ for EtO will prohibit some otherwise potentially viable alternative monitoring methods, including the Picarro air monitoring system and many open-path technologies. Commenters recommended that the EPA remove 40 CFR 63.184(i)(3) in its entirety. Commenters indicated that this requirement limits flexibility and the ability for evaluation of alternate methods via the EPA's current alternate methods processes.

A commenter further indicated that the proposed action levels for EtO and chloroprene are three times the RDL for each compound and, according to the EPA's technical memorandum, three times the RDL represents the level where a test method performs with acceptable precision. However, the commenter recommended that the EPA increase the multiplier to 5 for EtO for consistency with proposed EPA Method 327. The commenter argued that the requirement at 40 CFR 63.184(i)(3) for a ten-fold reduction in MDL for alternative test methods is so restrictive as to potentially eliminate the flexibility of real-time monitoring because the MDL was only five times lower than an already very low action level. The commenter suggested the EPA revise the language at 40 CFR 63.184(i)(3) to require methodologies with detection limits at or below those of the reference standard ( i.e., EPA Method 325A/B, EPA Method 327).

Response: The EPA agrees with the commenters that the proposed requirement that the MDL of the alternative method be at least an order of magnitude less than the action level is too restrictive, and, therefore, in the final rule we have revised the requirement at 40 CFR 63.184(i)(3) that the method detection limit of an alternative test method must be at least one-third of the action level for the compound(s) that will be monitored with the alternative method. The EPA considers three times the MDL to describe the limit of quantification of a method, or the point at which we have confidence in the accuracy and precision of a method. We note this requirement is also consistent with the EPA's approach for setting emission limits that are at least three times the RDL. Such an approach ensures that the standard is at a level that addresses measurement variability and is in a range that can be measured with reasonable precision. Requiring the detection limit of alternative measurement approaches to be at least one-third of the action level will ensure that measurements made near the action level are of reasonable precision.

We note that while the EPA has reduced the requirements for the minimum detection limit of alternative measurement approaches, when calculating the sampling period Δc, an owner or operator must still use zero as the lowest sample result when a measurement is below the MDL and must still use the MDL as the highest sample result if all sample results are below the MDL. The use of this approach in determining Δc incentivizes the use of technology capable of measuring the lowest possible concentration for the target compound.

b. NSPS

The EPA received comments in support of and against the proposed NSPS review, including our determination to include more stringent requirements for SOCMI equipment leaks, air oxidation unit processes, distillation operations, and reactor processes in the new NSPS subparts ( i.e., NSPS subparts VVb, IIIa, NNNa, and RRRa, respectively).

This section provides summaries of and responses to the key comments received regarding the NSPS review for SOCMI equipment leaks, air oxidation unit processes, distillation operations, and reactor processes. Comment summaries and the EPA's responses to additional issues raised regarding the proposed requirements resulting from our NSPS review are in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

i. Process Vents

Comment: Several commenters said that they opposed the EPA's proposal to eliminate the TRE index value concept in the new NSPS subparts IIIa, NNNa, and RRRa. The commenters provided the following arguments:

• The TRE index value has been an integral part of many technology-based air standards since its initial development, serving as a mechanism for determining cost effectiveness and triggering the requirements for process vent control (see,e.g., the preamble to the 1994 HON adoption, which states that the TRE concept is appropriate because it “can be used to reflect all possible combinations of various factors that affect emission rates and likelihood of current control” (citing 59 FR 19416) and “would provide consistency between the HON[,] the recently issued [control techniques guidelines] for SOCMI process vents. . .[and] the applicability criteria for the three SOCMI process vents NSPS” (59 FR 19418)). The EPA determined that BSER was 98 percent control (or an outlet concentration of 20 ppmvd at 3 percent O₂) of sources with a TRE less than or equal to 1.0 when it promulgated these rules.
• While the EPA discusses its basis for removing the TRE index value > 1.0 alternative emission standard, it provides no discussion for why the limited applicability exemption in the NSPS (TRE > 4.0 for NSPS subpart III and TRE > 8.0 for NSPS subparts NNN and RRR) is proposed to be removed. The EPA must explain why this exemption should be removed and provide an opportunity for the public to comment before taking final action to modify or remove it.
• Voluntary control of some process vents with a TRE index value greater than 1.0 does not imply that controlling all process vents with a TRE index value greater than 1.0 constitutes the BSER. While controlling a subset of process vents with a TRE index value greater than 1.0 may be cost effective, the EPA's cost analysis for controlling such vents significantly understates the cost of installing additional controls such as a thermal oxidizer.
• The fact that a control device at one stationary source controls multiple process vents (as opposed to a single process vent) does not mean that in all cases control of multiple process vents is cost-effective. If the cumulative emissions from the process vents are small, then even controlling all of them with one control device is not cost effective.
• The EPA's conclusion that the TRE index value calculation is theoretical, complex, uncertain, and difficult to enforce is overly broad and cannot be applied to the regulated industry as a whole. The issues the EPA cites related to calculation of the TRE index value do apply in instances with few organic compounds in the stream, and in instances where facilities have readily available process data obtained from source testing, other direct measurements, or permit limits. Observations from one facility's TRE index value calculation approach should not be construed as representative of 284 facilities.
• The EPA's cost analysis (see Docket Item No. EPA-HQ-OAR-2022-0730-0011) is not well supported and significantly underestimates the cost of installing and operating a thermal oxidizer. The EPA presents a total annual cost of $98,429 and a VOC emissions reduction of 9.1 tpy from the elimination of the TRE concept and the imposition of control requirements for all process vents. The EPA references the HON technology review memorandum in support of the cost calculations; however, that memorandum does not include a cost analysis of emission reduction calculations for NSPS sources. Furthermore, the EPA's proposed capital cost of $65,577 for a thermal oxidizer sized to control a 10 scfm stream is unrealistic; and it is also unrealistic to assume that a facility would install a thermal oxidizer simply for a 10 scfm stream. The EPA's cost algorithm significantly underestimates the costs associated with design and engineering of such projects. A commenter provided an example at one of their existing affected facilities where if NSPS NNNa is triggered via modification or reconstruction, the facility would need to install control equipment estimated at a conservative amount of $500,000 in order to control 0.07 tpy of VOC result from vents from recovery scrubbers, or about $7.14M per ton of VOC removed. The commenter suggested that if the EPA is going to eliminate the TRE concept, that the EPA consider a cost effectiveness cut-off that is scaled to inflation that could avoid absurd results such as this.
• The EPA has ignored the fact that facilities that would now be required to control Group 2 halogenated streams would not only have to control organic HAPs using a thermal oxidizer, but would also have to incur costs to design, engineer, and install controls for acid gas and dioxin/furan emissions.

A commenter questioned why removing the TRE concept for the SOCMI sector is not arbitrary given that no action was taken on the TRE concept in the recent RTR of the MON, conducted just 3 years ago.

Some commenters suggested that the EPA could keep the TRE index value concept but raise the threshold, or establish a mass-based criterion below which emission controls are not required such that the rules would only require control where it is cost-effective ( e.g., limit applicability of the NSPS to affected facilities at a site whose cumulative VOC emissions are greater than 25 tpy). A commenter pointed out that the proposed HON rulemaking requires control of process vents that emit greater than 1.0 lb/hr of total organic HAP, and suggested that a similar mass-based VOC emissions threshold below which control is not required be added to the SOCMI NSPS rules to avoid control being required for vent streams with very negligible VOC emissions. The commenter pointed out that the EPA included a mass-based emission threshold in NSPS subpart DDD at 40 CFR 60.560(g). The commenter provided an example of one of their distillation columns where the vacuum jet system vent emits very low amounts of VOC emissions (<0.0001 lb/hr uncontrolled), the net heating value is very low or negligible, and the vent stream contains primarily nitrogen and/or water vapor. The commenter said that they would have to then build an emission control device to manage this stream.

Response: As stated in the preamble to the proposed rule (88 FR 25080, April 25, 2023), the statutory review of these process vent NSPS (subparts III, NNN, and RRR) focused on whether there are any emission reduction techniques used in practice that achieve greater emission reductions than those currently required by the current NSPS and whether any such practices have become the BSER. Based on this review, we have determined that the BSER for reducing VOC emissions from these SOCMI processes remains combustion ( e.g., incineration, flares), and that the current emission standard of 98 percent reduction of TOC (minus methane and ethane) or reduction of TOC (minus methane and ethane) to an outlet concentration of 20 ppmv on a dry basis corrected to 3 percent oxygen continues to reflect the BSER.

While we found no change in the BSER for reducing VOC emissions from air oxidation units, distillation operations, and reactor processes, we are finalizing the removal of the entire TRE concept, including the alternative of maintaining a TRE index value greater than 1 without the use of control device and the limited applicability exemptions ( i.e., TRE > 4.0 for NSPS subpart III and TRE > 8.0 for NSPS subparts NNN and RRR) for purposes of NSPS subparts IIIa, NNNa, and RRRa. We stand by the rationale we provided in the preamble to the proposed rule for not including the TRE concept in NSPS subparts IIIa, NNNa, and RRRa, which is summarized as follows: (1) Based on the responses to our CAA section 114 request, we observed that some facilities are controlling continuous process vents that are not required by the NSPS subparts III, NNN, or RRR to be controlled per the results of the TRE index value calculation; (2) based on the responses to our CAA section 114 request, we observed that facilities are routing multiple continuous process vents to a single APCD; (3) determining a TRE index value for certain process vent streams is often theoretical, can be extremely complicated, and is uncertain; and (4) because the TRE index value is largely a theoretical characterization tool, it can be very difficult to enforce.

As stated in the preamble to the proposed rule (88 FR 25080, April 25, 2023), in reviewing an NSPS to determine whether it is “appropriate” to revise the standards of performance that reflects the degree of emission limitation achievable through application of BSER, the EPA considers the following information:

• Costs (including capital and annual costs) associated with implementation of the available pollution control measures.
• The amount of emission reductions achievable through application of such pollution control measures.
• Any non-air quality health and environmental impact and energy requirements associated with those control measures.
• Expected growth for the source category, including how many new facilities, reconstructions, and modifications may trigger NSPS in the future.
• Pollution control measures, including advances in control technologies, process operations, design or efficiency improvements, or other systems of emission reduction, that are “adequately demonstrated” in the regulated industry.
• Available information from the implementation and enforcement of current requirements indicating that emission limitations and percent reductions beyond those required by the current standards are achieved in practice.

As previously stated, some owners and operators do not use the TRE index value to determine whether a vent stream is required to be controlled. While we agree with commenters that owners and operators control vent streams that have a TRE index value greater than 1.0 for reasons other than the desire to avoid the TRE calculation, the fact is that owners and operators are controlling vent streams that have a TRE index value greater than 1.0 (possibly to comply with state or local regulations regarding VOCs or to meet a BACT limit), which is information relevant to our CAA section 111(b)(1)(B) review of the standards. Given that the TRE concept has been used since each original NSPS adoption, we consider owners and operators controlling vent streams that have a TRE index value greater than 1.0 to be a pollution control measure ( i.e., an advance in process operations) in our analysis. Additionally, the removal of the TRE concept simplifies the determination as to whether owners and operators must control a vent stream and thus, the applicability process is easier to implement.

We disagree with commenters' assertions that the EPA did not provide evidence that the TRE concept is largely theoretical and, as a result, difficult to verify. As identified in the document titled Clean Air Act Section 112(d)(6) Technology Review for Continuous Process Vents Located in the SOCMI Source Category that are Associated with Processes Subject to HON, Continuous Front-end and Batch Front-end Process Vents Associated with Processes Subject to Group I Polymers and Resins NESHAP, and Process Vents Associated with Processes Subject to Group II Polymers and Resins NESHAP (Docket Item ID No. EPA-HQ-OAR-2022-0730-0094), one facility that received the CAA section 114 request provided over 300 pages of modeled runs used to determine certain characteristics of their continuous process vents to be utilized as part of the TRE index value calculations. Reviewing this information revealed that in many cases, the facility struggled to unify the modeled runs with actual conditions at the facility and in some cases made arbitrary decisions to allow the model to function. While we agree with commenters that the TRE index value can be derived from less theoretical methods, other responses to the CAA section 114 request did not indicate how parameters used in the TRE index value calculations were determined and commenters did not provide sufficient information to show which methods were most common throughout industry. Given the theoretical nature of the TRE index value, the EPA maintains that verifying TRE index values is arduous because it can involve relying on significant process knowledge in order to confirm compositions of vent streams, vent stream flowrates, vent stream net heating values, and hourly emissions. It may also require verification of other facility assumptions ( e.g., operational conditions and constraints), especially if modeling was used. This logic applies equally to existing, new, and modified sources and thus is one of the reasons why the EPA is not including the TRE concept in NSPS subparts IIIa, NNNa, and RRRa as part of this rulemaking.

We agree with commenters that the TRE index value has been an integral part of many technology-based air standards since its initial development. In fact, we said as much in the document titled CAA 111(b)(1)(B) review for the SOCMI air oxidation unit processes, distillation operations, and reactor processes NSPS subparts III, NNN, and RRR (see Docket Item No. EPA-HQ-OAR-2022-0730-0011). The TRE concept is almost 40 years old; it was first introduced in a December 1984 EPA document (EPA-450/3-84-015; see attachment to Docket Item No. EPA-HQ-OAR-2022-0730-0011). However, even if it has been used in the past, we believe that for purposes of the new NSPS subparts NNNa, IIIa, and RRRa, certain aspects of its underlying development are clearly no longer applicable or appropriate. For example, the EPA stated in the 1984 supporting materials (EPA-450/3-84-015) that the Agency attempted to make the TRE index independent of inflation ( e.g., the EPA assumed fixed relative costs of various resources, such as carbon steel and electricity), yet it is impossible to ignore inflation in the TRE calculations due to the time that has passed since it was developed ( e.g., costs of carbon steel and electricity have undoubtedly increased since the development of the TRE index).

Although the TRE index value may allow owners and operators to allocate resources efficiently and ensure that the most significant emission sources are targeted for control, the current use of the TRE index value is only based on controlling a single vent stream with a single APCD. This is an unrealistic scenario when compared to how affected facilities actually control their vent streams; it is much more likely that a facility routes numerous vent streams to the same APCD (which is evident from observing the responses to our CAA section 114 request).

We do agree with commenters that our cost estimate for installing a new recuperative thermal oxidizer (to control vent streams subject to the NSPS) included in the proposed rule is unrealistic ( e.g., we severely underestimated flow rates needed to route vent streams with low flow to APCDs). Although we still believe the use of the EPA's control cost template is appropriate to estimate the cost of installing a new recuperative thermal oxidizer (to control vent streams subject to the NSPS), we revised our estimates to reflect the limitations of the correlations associated with the EPA's control cost template, which starts with a flow rate of 500 scfm. With these corrections, we estimate that the average TCI to install a new recuperative thermal oxidizer is about $167,000 (as opposed to the $66,000 estimate provided in the proposed rule). However, our estimate is still much less than the $500,000 estimate provided by commenters. One explanation for this is that commenters may have used a much higher flow rate ( e.g., 5,000 scfm as opposed to 500 scfm) and a “Regenerative Thermal Oxidizer” in their cost analysis instead of a “Recuperative Thermal Oxidizer.” Moreover, commenters did not provide supporting information for their estimated capital costs, so the EPA cannot corroborate their assertions regarding cost.

In light of the fact that commenters were generally concerned about the cost estimate for installing a new recuperative thermal oxidizer (to control vent streams subject to the NSPS), we performed additional analyses to evaluate the cost effectiveness of not including the TRE concept in the new NSPS IIIa, NNNa, and RRRa. Instead of using $500,000 as suggested by a commenter, we used a TCI of $1,000,000 and the EPA's control cost template (for installing a new recuperative thermal oxidizer with 70 percent energy recovery). Even with this change in our analysis, we continue to believe that revising the standard from a TRE calculation to control of all vent streams is still cost effective when considered along with the suite of process vent requirements evaluated as a whole under our NSPS review. As stated in the preamble to the proposed rule (88 FR 25080, April 25, 2023), we considered four different NSPS-triggering scenarios and a suite of proposed process vent requirements combined together (including not only revising the standard from a TRE calculation to control of all vent streams, but also new operating and monitoring requirements for flares, the addition of maintenance vent requirements, and the addition of adsorber monitoring requirements). In this context, we conclude that, even with our reevaluation of TCI for installing a new recuperative thermal oxidizer, the cost-effectiveness value of the suite of process vent requirements evaluated under our NSPS review is $4,890 per ton VOC (instead of $4,570 per ton VOC as proposed), which we consider to be reasonable. For further details on how we estimated cost and VOC emissions reductions, see the document titled CAA 111(b)(1)(B) review for the SOCMI air oxidation unit processes, distillation operations, and reactor processes NSPS subparts III, NNN, and RRR—FINAL, which is available in the docket for this rulemaking.

We disagree with the commenters' suggestion to include the TRE concept in the new NSPS subparts NNNa, IIIa, and RRRa but raise the TRE index value threshold to something greater than 1.0 (as opposed to not including the TRE concept in its entirety, as proposed). Regarding a commenter's assertion that removing the TRE concept is arbitrary given no action was taken on the TRE concept in the MON RTR, we note that we did not have data related to Group 2 process vents while developing revisions to the MON. Setting an emission threshold with no knowledge of which Group 2 MON vent streams would be impacted and the potential cost or reductions associated with that revision would not have been appropriate.

Finally, we agree with the commenter's request to include a mass-based criterion below which emission controls are not required, but only for NSPS subparts IIIa and NNNa (not NSPS subpart RRRa). We believe a mass-based exemption criterion is not needed for NSPS subpart RRRa given that we are finalizing, as proposed, a volumetric flowrate-based exemption (0.011 scm/min at 40 CFR 60.700a(c)(3)) as well as a concentration-based exemption (300 ppmv TOC as measured by EPA Method 18 or 150 ppmv TOC as measured by EPA Method 25A at 40 CFR 60.700a(c)(7)) in NSPS subpart RRRa. It is clear from supporting documents that the EPA included the concentration-based exemption in NSPS subpart RRR with the intent to relieve owners and operators of controlling vent streams with very low amounts of VOC emissions (see 58 FR 45948, August 31, 1993, as well as the document titled Selection of the Low Concentration Cutoff, which is available in the docket for this rulemaking). Even so, we recognize that NSPS subparts IIIa and NNNa do not contain these same exemptions. Therefore, we are finalizing a mass-based exemption criterion of 0.001 lb/hr TOC (for which emission controls are not required) for NSPS subparts IIIa and NNNa at 40 CFR 60.610a(c)(1) and 40 CFR 60.660a(c)(6), respectively. We based this criterion on the combination of both the volumetric flowrate- and concentration-based exemptions that are included in NSPS subparts RRR and the final RRRa. In other words, the 0.001 lb/hr TOC mass-based exemption criterion which we are finalizing in NSPS subparts IIIa and NNNa is roughly equal to a vent stream with a volumetric flowrate of 0.011 scm/min and a TOC concentration of 300 ppmv (assuming a TOC molecular weight of 80 grams per mole) included in NSPS subparts RRR and the final RRRa. We also note that new affected facilities should have greater flexibility in selecting cost-effective control options during the design and construction phase ( e.g., owners and operators at greenfield sources are likely to have more flexibility in spatial considerations compared to those at an existing source leading to a potential reduction in the amount of complex piping and construction materials needed to install an APCD).

Comment: A commenter said they support the EPA's proposal to eliminate the relief valve discharge exemption from the definition of “vent stream” in NSPS, subparts IIIa, NNNa, and RRRa such that any relief valve discharge to the atmosphere of a vent stream is a violation of the emissions standard. However, several other commenters opposed this proposal. Commenters requested that the EPA revise the term “violation” to “deviation” in NSPS subparts IIIa (at 40 CFR 60.612a(b)), NNNa (at 40 CFR 60.662a(b)), and RRRa (at 40 CFR 60.702a(b)) regarding the prohibition of relief valve discharges ( e.g., PRD releases to the atmosphere) and use of bypass lines. In addition, the commenters requested that the EPA add the same PRD work practice standard that the EPA has finalized in the MON (at 40 CFR 63.2480(e)(3)- (8)) and Ethylene MACT (at 40 CFR 63.1107(h)(3)-(8)), and proposed in the HON (at 40 CFR 63.165(e)), into NSPS subparts IIIa, NNNa, and RRRa at 40 CFR 60.612a(d), 60.662a(d), and 60.702a(d), respectively. The commenters argued that the proposed regulatory approach regarding eliminating the relief valve discharge exemption does not represent BSER for the SOCMI source category given that relief valve discharges that are routed to the atmosphere are necessary at times for at least the following reasons:

• Hazardous oxidation products: A discharge to a flare would result in combustion products that are not desirable.
• Chemical reactivity within flare system: Some affected facilities may use a single large flare for emission control for a given process area or group of process areas.
• Physical obstruction within flare header system: In some cases, there is a potential for certain compounds to block or restrict portions of the flare header.
• Streams containing oxygen: Some process streams and equipment that PRDs protect contain mixtures of organic compounds and oxygen especially in air oxidation processes. Some air oxidation reactors have rupture discs as PRDs, and swings in air supply can cause a rupture disc to fail.
• Intolerable backpressure on the PRD: The operating pressure in a large flare header system could increase from just slightly over atmospheric pressure to a pressure in the 10-20 psig range or higher for certain periods of time when upset venting occurs or another highly intermittent flow occurs.
• Intolerable liquid load on the flare Knock Out (KO) drum: If the PRD is in liquid service, it is not acceptable to add a high-volume liquid discharge from a PRD into a flare header. Flare KO drums have a finite liquid capacity. If the liquid is highly volatile, severe pipe contraction (due to auto-refrigeration) can potentially cause a loss-of-containment failure of the flare header piping.
• Technically impossible to collect discharges from PRDs on portable/mobile containers.
• It is not technically or economically feasible to install a new large flare system to capture the discharge from a small number of new PRDs from a new, reconstructed, or especially a modified SOCMI source regulated under NSPS subparts IIIa, NNNa, and RRRa.
• Any chemical manufacturing facility with the potential to release high volumes of chlorinated (halogenated) material from a PRD release would be required to install and operate an oversized thermal oxidizer equipped with acid gas controls that would be operated on stand-by anytime the facility is in operation; and this operating mode results in the facility also emitting large amounts of secondary emissions such as greenhouse gases, VOCs, NO_X, and CO.
• PRDs prevent catastrophic breaches of process equipment that could endanger both the lives of plant employees and nearby communities, and result in damage to property; these catastrophic breaches would result in much greater emissions than those resulting from a PRD release. PRDs minimize the loss of process materials to the surrounding environment.

Commenters also argued that it is not cost-effective to route all PRDs to control devices. Some commenters pointed out that given that the EPA concluded it is not cost-effective to route all PRDs to control for HON and P&R (and instead proposed a work practice standard for PRDs that vent to the atmosphere), it is unclear how the Agency could presume such a requirement would be cost-effective as BSER and appropriate to establish as an NSPS requirement. Additionally, the commenters asserted that the only analysis the EPA uses to justify the proposed change is the identification of a single lowest achievable emissions rate (LAER) condition in the reasonably available control technology (RACT)/BACT/LAER clearinghouse database. The commenters argued that by equating a single LAER determination (based on the EPA's RACT/BACT/LAER clearinghouse database search regarding ID TX-0813171 for the “Linear Alpha Olefins Plant,” which is operated by INEOS Oligomers USA, LLC) to BSER and not performing any additional analysis, the EPA has ignored the statutory requirements of CAA Section 111(a)(1) in that the Agency did not adequately account for the cost of achieving reductions, nor did the Agency consider non-air quality health and environmental impacts and more specifically, energy requirements.

A commenter added that PRDs serve a vitally important role as the last line of defense to protect vessels and equipment from mechanical failure should an overpressure situation occur; therefore, it is important that they work correctly. The commenter asserted that in the unlikely event that a pressure relief event occurs, it is important to have the opportunity to analyze such situations and implement corrective actions to further minimize the chance that such an event will occur in the future.

Response: We disagree with the commenters that the removal of the exemption for PRD releases to atmosphere is not BSER for NSPS subparts IIIa, NNNa, and RRRa and that the EPA has ignored its obligations to CAA section 111. For a thorough explanation of our BSER analysis and the ways in which the EPA complied with the statutory requirements of CAA section 111, refer to the document titled CAA 111(b)(1)(B) review for the SOCMI air oxidation unit processes, distillation operations, and reactor processes NSPS subparts III, NNN, and RRR (see Docket Item No. EPA-HQ-OAR-2022-0730-0011) and section III.C.3.b of the proposal preamble (88 FR 25080, April 25, 2023). No changes are being made to the final rule as a result of this comment.

While commenters state that only one facility was identified as part of the RACT/BACT/LAER clearinghouse database, we note that one additional facility was also identified as having prohibitions on PRDs releasing to the atmosphere and were thus choosing to route those pieces of equipment to an APCD. The Lyondell Chemical Bayport Choate Plant in Harris, TX (permit number 137789) was identified as part of our RACT/BACT/LAER clearinghouse database search, but did not properly state that they were also under restrictions for PRD releases to atmosphere for streams containing more than 1 percent VOC. See the updated document titled CAA 111(b)(1)(B) review for the SOCMI air oxidation unit processes, distillation operations, and reactor processes NSPS subparts III, NNN, and RRR—FINAL, which is available in the docket for this rulemaking. Lyondell and the Linear Alpha Olefins Plant were placed under these restrictions by the state of Texas in 2017 and 2015, respectively. In fact, the TCEQ published the document titled Air Permit Technical Guidance for Chemical Sources Fugitive Guidance in June 2018, which is available in the docket for this rulemaking. Section III of the document states that “the following practices are generally considered to be the minimum for BACT . . . . New relief valves are required to vent to a control device for any potential releases and as a result, any fugitive emissions are reduced. Exceptions may be made if venting relief valve to control will result in a safety concern, but this does not exempt the company from controls such as equipping the valve with a rupture disk and pressure sensing-device.” The EPA maintains that between the guidance provided by the TCEQ and ability of the two identified facilities to meet the requirements, prohibiting PRD releases to atmosphere is adequately demonstrated for purposes of determining BSER.

We also disagree with commenters' descriptions of why PRDs releasing to atmosphere are necessary. We note that owners and operators are not obligated to route PRDs to an APCD. In fact, we agree with commenters that PRDs act as a last line of defense in uncommon process conditions. Therefore, the EPA expects that a well-controlled and rigorously designed process will not experience PRD releases regularly, if at all. In those situations, as described by the commenter, where PRD releases are necessary to prevent further catastrophic failure, we agree with the commenter that safety is a priority and PRD releases may be necessary. However, we note that we are not prohibiting the release of PRDs in totality, just to atmosphere, or their use in general and that process conditions leading to catastrophic failure should be well outside regular operating conditions. Therefore, the EPA expects that PRDs used to prevent catastrophic failure can continue to function without reasonable concern for release to atmosphere during regular operating conditions. If the facility is concerned about a PRD releasing to atmosphere during a catastrophic failure event, which should be exceptionally rare to begin with, they may choose to route those emissions to an APCD to avoid incurring a violation. The EPA maintains that releasing uncontrolled volumes of emissions to atmosphere as a result of preventable process upsets is characteristic of a violation.

To that point, we are not requiring owners or operators to route PRD releases to an APCD, and there are no cost, non-air quality health, environmental, or energy requirements as a result of this change. The EPA expects no additional equipment will be needed for facilities to meet the finalized provisions given our agreement with commenters that PRD releases are unlikely to occur at all assuming a process is rigorously designed, maintained, and controlled. If the owner or operator chooses to control PRD emissions, it is their responsibility to select whichever control method is most appropriate considering, among other factors, the composition of the release, location of the equipment, and overall safety. We note that facilities with new sources that choose to route PRD emissions to an APCD will have the flexibility in the design and construction phase to select options they consider to be cost-effective and plan based on key criteria like placement of the equipment. For existing sources that trigger the NSPS subpart IIIa, NNNa, or RRRa via a modification or reconstruction, it is the responsibility of the owner or operator to make the determination if retrofitting PRDs to release to an APCD is feasible, cost-effective, and necessary against the potential to incur violations as a result of atmospheric release or if alternative process controls or operational practices are more appropriate. Any cost, non-air quality health, environmental, or energy impacts associated with the owner or operator controlling PRD emissions, including those from halogenated streams as identified by the commenter, were not considered as part of the BSER analysis because they are only incurred at the discretion of an owner or operator if they choose to go beyond the requirements of this rulemaking and pursue control of emissions. For the above reasons, the EPA has met its obligations under CAA section 111(a)(1).

We disagree with the commenter that the use of the term “violation” should be replaced with “deviation” in NSPS subparts IIIa (at 40 CFR 60.612a(b)), NNNa (at 40 CFR 60.662a(b)), and RRRa (at 40 CFR 60.702a(b)). We used the term “violation” in the SOCMI NSPS (subparts IIIa, NNNa, and RRRa) to be consistent with the HON standards that also regulate the SOCMI source category.

ii. Equipment Leaks

Comment: A commenter contended the EPA's BSER analysis was insufficient because it failed to consider key equipment leak control technologies, such as OGI, leak detection sensor networks (LDSNs), and even options that the EPA previously considered in 2007 when developing NSPS subpart VVa. The commenter asserted that the EPA must consider these developments when evaluating and establishing the BSER for new, reconstructed, and modified SOCMI process units. The commenter stated that the EPA's review of the LDAR requirements in NSPS subpart VVa is inconsistent with other reviews of NSPS equipment leak standards. In particular, the commenter noted that in its November 15, 2021 proposal for the Crude Oil and Natural Gas source category, the EPA evaluated several monitoring techniques, and combinations of techniques, to determine if the BSER for equipment leaks at natural gas processing plants should be revised, including bimonthly and quarterly OGI monitoring in combination with annual EPA Method 21 monitoring at a leak definition of 10,000 ppm, and bimonthly OGI monitoring on all equipment with the potential for VOC emissions. The commenter asserted that the EPA's failure to consider OGI is erroneous considering the EPA has established an Alternative Work Practice at 40 CFR 60.18(g) through (i) that allows sources subject to NSPS subparts VV and VVa to conduct bimonthly OGI monitoring with annual EPA Method 21 surveys at 500 ppm as an alternative to conducting EPA Method 21 monitoring at the leak definitions and frequencies in those subparts. The commenter added that at a minimum, the EPA should evaluate whether this alternative work practice now represents the BSER for NSPS subpart VVb.

Response: For the reasons explained below, we find that none of the control options raised in the comment above ( i.e., OGI, LDSN and options considered in the last review) is BSER for equipment leaks from new, modified, and reconstructed SOCMI process units.

Regarding OGI, we do not believe it replaces EPA Method 21 as BSER for equipment leaks from SOCMI process units for the following reasons. First, as shown by our equipment leaks regulations for the SOCMI industry since the early 1980s, leaks in the area of 500 to 1000 ppm can be detected using EPA Method 21 and repaired for most equipment in this industry. The EPA acknowledges that OGI is effective at finding large leaks quickly for many compounds, but, while OGI is capable of detecting low-level leaks under certain conditions, it is difficult for a camera operator to find low level-leaks with OGI under the range of conditions that leak surveys are generally conducted, including variable ambient and equipment temperatures, complex backgrounds, and elevated wind speeds. Additionally, the compounds that can be detected by an OGI camera are limited to the compounds that have a peak in the spectral range of the filter on the OGI camera (generally around 3.2-3.4 micron for cameras used to detect hydrocarbons). While many compounds of interest do have a peak in this range, the variety of chemicals found at SOCMI facilities is very broad, and not all of these chemicals can be observed with an OGI camera. For example, ethylene and acetaldehyde have very weak peaks in the spectral range common to OGI camera filters, making it extremely difficult to see these compounds with an OGI camera. For those compounds that can be observed with an OGI camera, the detection range of the camera varies, and some compounds must be emitted in high quantities before being observed. For example, it is expected that twice as much styrene must be emitted as xylene (any isomer) before the emissions are visible with an OGI camera. For these reasons, the use of OGI is not appropriate for the SOCMI source category.

Regarding LDSNs, which use an array of continuous sensors to find leaks, we agree that these systems can effectively be used to trigger and target EPA Method 21 or OGI monitoring and leak repair, but an effective system depends on the sensitivity of the sensors, the spacing of the sensors, and the trigger used to deploy a ground monitoring crew. It is difficult to develop vendor-agnostic monitoring requirements that can be incorporated generically within a rule, and we do not have the necessary information to do so at this time. While we are continuing to look at how to develop a standardized approach for sensor networks, we are not prepared to include provisions for a continuous sensor network for the SOCMI source category at this time. However, owners or operators can elect to submit a request for an alternative means of emission limitation for using a site-specific sensor network monitoring plan.

Finally, the commenter claims that the EPA must evaluate options that we had previously considered while promulgating NSPS subpart VVa in 2007. The EPA does not have information, nor has the commenter provided any, indicating that there has been development since the last review to any such previously rejected option that warrants evaluation in the present review.

Comment: A commenter stated that the EPA's focus on lowering the leak definition for valves from 500 ppm to 100 ppm is inconsistent with recent EPA focus on targeting large emissions sources, as was done for the oil and gas industry. The commenter stated that rulemaking targeted finding large leaks faster, while in the review for NSPS subpart VVa, the EPA focused on reducing a small population of small leaks by lowering the leak definition for valves from 500 ppm to 100 ppm. The commenter added that the EPA's analysis for NSPS subpart VVa demonstrates this proposed change only results in reducing 0.64 tpy of VOC emissions per affected facility beyond the baseline. The commenter also stated that the facility-level leak inspection data that the EPA has available shows that leaks between 100 ppm and 500 ppm are not very common. The commenter specified that the EPA has access to at least one data set containing leak inspection results for nearly 3,000 components at a chemical manufacturing facility. The commenter added that the average EPA Method 21 reading was over 25,000 ppm, with the minimum reading for valves was 747 ppm and minimum reading for connectors was 1,000 ppm, underscoring the importance of entirely preventing significant leaks (as well as quickly identifying and remediating others). The commenter recommended, in addition to strengthening the standards as it has proposed, that the EPA evaluate the use of additional technology, such as low emission valves and valve packing and connectors less likely to leak, in order to prevent the presence of these large emissions. The commenter concluded that this evaluation would allow the EPA to take action on preventing emissions from occurring at these high rates and potentially result in the determination that a combined program of low-emissions technology with regular EPA Method 21 monitoring and leak repairs is the BSER for SOCMI equipment leaks.

Response: The EPA disagrees that the actions taken in this NSPS rulemaking are inconsistent with the actions taken in other recent NSPS rulemakings, specifically the oil and gas NSPS (see 89 FR 16820 (March 8, 2024)). The rulemaking for the oil and gas sector are focused on finding large leaks faster while the leak regulation for SOCMI does not, because there are key differences between the oil and gas and the SOCMI source category. The SOCMI industry has been complying with equipment leak regulations since the early 1980s, and leaks are expected to be much lower in SOCMI than for the oil and gas industry. As a result, the leak definitions that SOCMI facilities must comply with are already very low, 500 to 1000 ppm for most equipment, and the proposed and final rule lowers leak definitions to 100 ppm for valves to gain even more emissions reductions.

Additionally, the data set referenced by the commenter was collected over several years. The chemical facility associated with the data set conducted an OGI survey and then recorded the EPA Method 21 reading for any leaks found by OGI. However, the data set does not include any information related to leaks that could have been found with EPA Method 21 but not OGI. Therefore, the EPA cannot conclude that there are few leaks between 100 ppm and 500 ppm at chemical plants based on this data set. What this data set does demonstrate is that there is no evidence that OGI can find low-level leaks at chemical plants.

In the final rule (NSPS subpart VVb), we are not requiring specific types of equipment be used to meet the 100 ppm leak definition for valves. However, in order to meet the 100 ppm leak definition for valves, we anticipate that facilities will need to use low-emission valves or packings. The average cost-effectiveness (with recovery credits) of lowering the leak definition for valves in gas/vapor or light liquid service from 500 ppm to 100 ppm, is $2,780 per ton of VOC reduced, and the EPA estimates this provision could result in reductions of more than 20 tpy of VOC.

Comment: A commenter contended that the EPA's proposed definition for capital expenditures in NSPS subpart VVb narrows the reach of modification and would result in the exclusion of certain process units from applicability to the subpart through modification. For NSPS subpart VVb, the commenter opposed the two proposed calculations for “X”. The commenter explained that by proposing a value for “X” to be “2023 minus the year of construction” for sources with a construction date after January 6, 1982 and before January 1, 2023, the EPA has categorically exempted any process unit from ever becoming subject to NSPS subpart VVb through modification if its date of construction is prior to January 6, 1982. The commenter contended that this error must be addressed in the final rule to not create a loophole exempting the oldest of these SOCMI process units from ever becoming subject to NSPS subpart VVb through modification. The commenter suggested revising the value for “X” to mean “2023 minus the year of construction” without the need to bookend this definition with specific dates. The commenter added that the EPA should first evaluate more recent developments on the definition of “capital expenditure” inclusion in the final NSPS subpart VVb. The commenter also opposed the proposed change of “X” for sources constructed in the year 2023 in order for X to not be equal to zero, which results in an equation that cannot be solved. The commenter noted that the EPA has addressed this same issue recently through specific changes to the definition of capital expenditure promulgated in the technical amendments to NSPS subpart OOOOa for equipment leaks at onshore natural gas processing plants. The commenter explained that in those amendments, the EPA revised the equation used to determine “Y” (the percent of replacement costs) to remove the variable “X” (and logarithmic function) and instead the EPA specifically defined “Y” as “the Consumer Price Index (CPI) of the date of construction divided by the most recently available CPI of the date of the project, or “CPIN/CPIPD”. The commenter contended that at a minimum, the EPA must consider this calculation of “Y” when defining “capital expenditure” in NSPS subpart VVb and discuss why the use of the CPI-based ratio is not appropriate for affected facilities before finalizing the proposed definition with the appropriate revisions to close loopholes.

Response: We agree with the commenter that in the proposed definition of “capital expenditure” in NSPS subpart VVb, the value of “X” should not be bounded by the NSPS subpart VV date of January 6, 1982. We also agree with the commenter that we should update the definition of “capital expenditure” to use the CPI in the equation for “Y” in NSPS subpart VVb. For the reasons discussed below, the EPA is finalizing the capital expenditure definition in NSPS subpart VVb to state in part that the value of “Y” is calculated using the CPI of the date of original construction of the process unit divided by the most recently available CPI of the date of the project.

In the early 1980s, some facilities were having trouble determining capital expenditure because records for costs were not available for determining the original basis of the affected facility. The EPA developed an alternative method to NSPS subpart A which enabled companies to use replacement cost rather than original cost. In the alternative method, an inflation index is applied to the replacement cost to approximate the original cost basis of the affected facility. The relationship between the replacement and original cost ultimately ended up in the formulas contained in the definitions of “capital expenditure” in NSPS subparts VV and VVa.

The formulas for “Y” in the definitions of “capital expenditure” in NSPS subparts VV and VVa were intended to adjust the replacement cost for inflation to approximate the original cost basis; however, the formulas were based on analysis of inflation between the years 1947 and 1982 and do not necessarily reflect current economic conditions. In the 2020 amendments to NSPS subpart OOOOa, which covers the oil and natural gas sector, the EPA determined that using a CPI-based ratio is more appropriate under current economic conditions. Similarly, the EPA has determined the CPI-based ratio better reflects the inflation of chemical process facility construction costs over time and thus is more appropriate for use in determining capital expenditure for the SOCMI source category in NSPS subpart VVb. There are several versions of the CPI published by the U.S. Bureau of Labor Statistics; for simplicity, the EPA is requiring the use of “CPI-U, U.S. city average, all items” (CPI for all urban consumers) for both CPI values.

4. What is the rationale for our final approach and final decisions for the technology review and NSPS review?

a. NESHAP

Our technology review focused on the identification and evaluation of developments in practices, processes, and control technologies that have occurred since the previous technology reviews for the HON and the P&R I and P&R II NESHAP were promulgated (see 71 FR 76603, December 21, 2006; 73 FR 76220, December 16, 2008; and 77 FR 22566, April 21, 2011 for additional details). Specifically, we focused our technology review on all existing MACT standards for the various emission sources in the SOCMI, P&R I, and P&R II source categories, including, heat exchange systems, storage vessels, process vents, transfer racks, wastewater, and equipment leaks. Under CAA section 112(d)(6), we also proposed a fenceline monitoring work practice standard requiring owners and operators to monitor for any of six specific HAP ( i.e., benzene, 1,3-butadiene, ethylene dichloride, vinyl chloride, EtO, and chloroprene) if their site uses, produces, stores, or emits any of them, and conduct root cause analysis and corrective action upon exceeding the annual average concentration action level set forth for each HAP. In the proposal, we identified cost-effective developments only for HON and P&R I heat exchange systems, storage vessels, and process vents, and we proposed to revise the standards for these three emissions sources under the technology review. We did not identify developments in practices, processes, or control technologies (beyond the fenceline monitoring work practice standard) for transfer racks, wastewater, and equipment leaks. Further information regarding the technology review can be found in the proposed rule (88 FR 25080, April 25, 2023) and in the supporting materials in the rulemaking docket at Docket ID No. EPA-HQ-OAR-2022-0730.

During the public comment period, we received several comments on our proposed determinations for the technology review. The comments and our specific responses and rationale for our final decisions can be found in section IV.B.3 of this preamble and in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking. No information presented by commenters has led us to change our proposed determination under CAA section 112(d)(6) for transfer racks, wastewater, and equipment leaks, and we are finalizing our determination that no changes to these standards are warranted. However, based on comments received on the proposed revisions for the Group 1 HON and P&R I storage vessels, we are clarifying that the capacity and MTVP thresholds in the final rule apply to both new and existing sources. In addition, some additional cost information was submitted by commenters on the proposed revisions for HON process vents and P&R I continuous front-end process vents. Based on these comments, we have updated our cost analysis, but continue to believe our revisions for HON process vents and P&R I continuous front-end process vents, as proposed, are still cost-effective. Therefore, for HON process vents and P&R I continuous front-end process vents, we are finalizing, as proposed the: (1) Removal of the TRE concept in its entirety; (2) removal of the 50 ppmv and 0.005 scmm Group 1 process vent thresholds; and (3) redefining of a Group 1 process vent (require control) as any process vent that emits ≥1.0 lb/hr of total organic HAP. Finally, based on comments received on the proposed fenceline monitoring requirements, we have established two action levels in the final rule for chloroprene ( i.e., one action level under CAA section 112(d)(6) for this HAP and another action level under CAA section 112(f)) in lieu of only one action level, as proposed). In addition, based on comments received, we are: (1) Finalizing burden reduction measures to allow owners and operators to skip fenceline measurement periods for specific monitors with a history of measurements that are at or below certain action levels; (2) clarifying that fenceline monitoring is required for owners and operators with affected sources that produce, store, or emit one or more of the target analytes; (3) reducing the requirements for the minimum detection limit of alternative measurement approaches; (4) clarifying how owners and operators establish the monitoring perimeter for both sorbent tubes and canisters; (5) clarifying the calculation of Δc when a site-specific monitoring plan is used to correct monitoring location concentrations due to offsite impacts; (6) changing the required method detection limit for alternative test methods from an order of magnitude below the action level to one-third of the action level; and (4) with the exception of fenceline monitoring of chloroprene at P&R I affected sources producing neoprene, we are changing the compliance date in the final rule to begin fenceline monitoring 2 years (instead of 1 year, as proposed) after the effective date of the final rule. For P&R I affected sources producing neoprene, we have changed the compliance date for fenceline monitoring of chloroprene to begin no later than October 15, 2024, or upon startup, whichever is later, subject to the owner or operator seeking the EPA's authorization of an extension of up to 2 years from July 15, 2024.

b. NSPS

For NSPS subparts IIIa, NNNa, and RRRa, we are finalizing the suite of process vent requirements, as proposed. As described in the proposal (88 FR 25080, April 25, 2023) and in consideration of comments received about these new requirements (see section IV.B.3.b.i of this preamble for further detail), we found the requirements to be cost-effective for VOC emission reductions at new, modified, and reconstructed affected facilities.

For NSPS subpart VVb, we are finalizing, as proposed, the same requirements in NSPS subpart VVa with the updated requirement that all gas/vapor and light liquid valves be monitored monthly at a leak definition of 100 ppm instead of 500 ppm, and an additional requirement that all connectors be monitored once every 12 months at a leak definition of 500 ppm, as described in the proposal (88 FR 25080, April 25, 2023).

C. Amendments Pursuant to CAA Section 112(d)(2) and (3) and 112(h) for the SOCMI, P&R I, and P&R II Source Categories NESHAP

1. What did we propose pursuant to CAA section 112(d)(2) and (3) and 112(h) for the SOCMI, P&R I, and P&R II source categories?

Under CAA sections 112(d)(2) and (3), we proposed to amend the operating and monitoring requirements for a subset of flares in the SOCMI and P&R I source categories. We proposed at 40 CFR 63.108 (for HON) and 40 CFR 63.508 (for the P&R I NESHAP) to directly apply the petroleum refinery flare rule requirements in 40 CFR part 63, subpart CC, to the HON and P&R I flares with clarifications, including, but not limited to, specifying that several definitions in 40 CFR part 63, subpart CC, that apply to petroleum refinery flares also apply to the flares in the specified subset, adding a definition and requirements for pressure-assisted multi-point flares, and specifying additional requirements when a gas chromatograph or mass spectrometer is used for compositional analysis. Specifically, we proposed to retain the General Provisions requirements of 40 CFR 63.11(b) and 40 CFR 60.18(b) such that HON and P&R I flares operate pilot flame systems continuously and that these flares operate with no visible emissions (except for periods not to exceed a total of 5 minutes during any 2 consecutive hours) when the flare vent gas flow rate is below the smokeless capacity of the flare. We also proposed to consolidate measures related to flare tip velocity and new operational and monitoring requirements related to the combustion zone gas for HON and P&R I flares. Further, in keeping with the elimination of the SSM exemption, we proposed a work practice standard related to the visible emissions limits during periods when a HON or P&R I flare is operated above its smokeless capacity ( e.g., periods of emergency flaring). We proposed eliminating the cross-references to the General Provisions and instead specifying all operational and monitoring requirements that are intended to apply to HON and P&R I flares in the applicable subparts.

In addition, we proposed provisions and clarifications in the HON and P&R I and P&R II NESHAP for periods of SSM and bypasses, including PRD releases, bypass lines on closed vent systems, maintenance vents and equipment openings, storage vessel degassing, and planned routine maintenance for storage vessels to ensure that CAA section 112 standards apply continuously, consistent with Sierra Club v. EPA 551 F. 3d 1019 (D.C. Cir. 2008).

For PRD releases, we proposed revisions to the definition of “pressure relief device” for the HON and P&R I NESHAP, a definition of “relief valve” for the HON and P&R I NESHAP, and a definition in the P&R II NESHAP for “pressure relief device.” Under CAA section 112(h), we proposed a work practice standard for PRDs at 40 CFR 63.165(e) (for HON) and 40 CFR 63.502(a)(1) and (a)(2) (which references 40 CFR 63.165, for the P&R I NESHAP) that consists of using at least three prevention measures and performing root cause analysis and corrective action in the event that a PRD does release emissions directly to the atmosphere. (Examples of prevention measures include flow indicators, level indicators, temperature indicators, pressure indicators, routine inspection and maintenance programs or operator training, inherently safer designs or safety instrumentation systems, deluge systems, and staged relief systems where the initial PRD discharges to a control system.) We proposed that PRDs in EtO service (for HON) and PRDs in chloroprene service (for Neoprene Production processes subject to the P&R I NESHAP) may not vent directly to atmosphere. We also proposed to require that sources monitor PRDs that vent to atmosphere using a system that is capable of identifying and recording the time and duration of each pressure release and of notifying operators that a pressure release has occurred. We proposed at 40 CFR 63.165(e)(4) that PRDs that vent through a closed vent system to a control device or to a process, fuel gas system, or drain system must meet minimum requirements for the applicable control system. In addition, we proposed at 40 CFR 63.165(e)(5) that the following types of PRDs would not be subject to the work practice standard for PRDs that vent to the atmosphere: (1) PRDs in heavy liquid service; (2) PRDs that are designed solely to release due to liquid thermal expansion; (3) PRDs on mobile equipment; and (4) pilot-operated and balanced bellows PRDs if the primary release valve associated with the PRD is vented through a control system. Finally, we proposed at 40 CFR 63.165(e)(8) to require future installation and operation of non-flowing pilot-operated PRDs at all affected sources.

For bypass lines on closed vent systems, we proposed at 40 CFR 63.114(d)(3), 40 CFR 63.127(d)(3), 40 CFR 63.148(f)(4), and 40 CFR 63.172(j)(4) (for HON), and 40 CFR 63.485(x), 40 CFR 63.489(d)(3), and 40 CFR 63.502(a)(2) (for the P&R I NESHAP) that an owner or operator may not bypass the APCD at any time, that a bypass is a violation (at 40 CFR 63.118(a)(5) and (f)(7), 40 CFR 63.130(a)(2)(iv), (b)(3), and (d)(7), 40 CFR 63.148(i)(3)(iii) and (j)(4), Tables 3, 7, and 20 to 40 CFR 63, subpart G, 40 CFR 63.181(g)(3)(iii), and 40 CFR 63.182(d)(xix) (for HON), and 40 CFR 63.485(x), 40 CFR 63.489(d)(3), and 40 CFR 63.502(a)(2) (for the P&R I NESHAP)), and the owner or operator must estimate and report the quantity of organic HAP released.

Under CAA section 112(h), we proposed a work practice standard for maintenance vents and equipment openings at 40 CFR 63.113(k)(1)(i) (for HON), and at 40 CFR 63.485(x) and 40 CFR 63.487(i)(1)(i) (for the P&R I NESHAP) requiring that, prior to opening process equipment to the atmosphere, the equipment must either (1) be drained and purged to a closed system so that the hydrocarbon content is less than or equal to 10 percent of the LEL; (2) be opened and vented to the atmosphere only if the 10-percent LEL cannot be demonstrated and the pressure is less than or equal to 5 psig, provided there is no active purging of the equipment to the atmosphere until the LEL criterion is met; (3) be opened when there is less than 50 lbs of VOC that may be emitted to the atmosphere; or (4) for installing or removing an equipment blind, depressurize the equipment to 2 psig or less and maintain pressure of the equipment where purge gas enters the equipment at or below 2 psig during the blind flange installation, provided none of the other proposed work practice standards can be met.

Also under CAA section 112(h), we proposed a work practice standard for storage vessel degassing at 40 CFR 63.119(a)(6) (for HON) and 40 CFR 63.484(a) and (t) (which references 40 CFR 63.119, for the P&R I NESHAP) to allow storage vessels to be vented to the atmosphere once a storage vessel degassing concentration threshold is met ( i.e., once the vapor space concentration is less than 10 percent of the LEL) and all standing liquid has been removed from the vessel to the extent practicable. In addition, we proposed at 40 CFR 63.119(e)(7) that owners and operators would not be permitted to fill the storage vessel during these periods (such that the vessel would emit HAP to the atmosphere for a limited amount of time due to breathing losses only).

To address regulatory gaps, we proposed:

Emission limits for dioxins and furans at 40 CFR 63.113(a)(5) (for HON), 40 CFR 63.485(x) and 40 CFR 63.487(a)(3) and (b)(3) (for the P&R I NESHAP), and 40 CFR 63.523(e), 40 CFR 63.524(a)(3), and 40 CFR 63.524(b)(3) (for the P&R II NESHAP).

To define pressure vessel at 40 CFR 63.101 (for HON) and 40 CFR 63.482 (for the P&R I NESHAP) to mean “a storage vessel that is used to store liquids or gases and is designed not to vent to the atmosphere as a result of compression of the vapor headspace in the pressure vessel during filling of the pressure vessel to its design capacity,” and to remove the exemption for “pressure vessels designed to operate in excess of 204.9 kilopascals and without emissions to the atmosphere” from the definition of storage vessel. We proposed LDAR requirements at 40 CFR 63.119(a)(7) (for HON) and 40 CFR 63.484(t) (for the P&R I NESHAP) requiring no detectable emissions at all times ( i.e., would be required to meet a leak definition of 500 ppm at each point on the pressure vessel where total organic HAP could potentially be emitted); initial and annual leak monitoring using EPA Method 21 of 40 CFR part 60, Appendix A-7; and routing organic HAP through a closed vent system to a control device ( i.e., no releases to the atmosphere through a pressure vessel's PRD).

A requirement at 40 CFR 63.170(b) (for HON) and 40 CFR 63.485(d) (for the P&R I NESHAP) that owners and operators of all surge control vessels and bottoms receivers that emit greater than or equal to 1.0 lb/hr of total organic HAP would be required to reduce emissions of organic HAP using a flare meeting the proposed operating and monitoring requirements for flares; or reduce emissions of total organic HAP or TOC by 98 percent by weight or to an exit concentration of 20 ppmv.

Removing the exemption for transfer operations that load “at an operating pressure greater than 204.9 kilopascals” from the definition of transfer operation at 40 CFR 63.101 (for HON) such that owners and operators would be required to equip each transfer rack with an operating pressure greater than 204.9 kilopascals with a vapor collection system and control device to reduce total organic HAP emissions by 98 percent by weight or to an exit concentration of 20 ppmv.

Requirements at 40 CFR 63.523(d) (for BLR manufacturers subject to the P&R II NESHAP) and 40 CFR 63.524(c) (for WSR manufacturers subject to the P&R II NESHAP) that owners and operators of each affected source comply with the requirements of 40 CFR 63.104 for heat exchange systems, including quarterly monitoring for existing and new heat exchange systems (after an initial 6 months of monthly monitoring) using the Modified El Paso Method and a leak definition of 6.2 ppmv of total strippable hydrocarbon concentration (as methane) in the stripping gas. We also proposed at 40 CFR 63.104(j)(3) a delay of repair action level of total strippable hydrocarbon concentration (as methane) in the stripping gas of 62 ppmv, that if exceeded during leak monitoring, would require immediate repair ( i.e., the leak found cannot be put on delay of repair and would be required to be repaired within 30 days of the monitoring event). In addition, we proposed at 40 CFR 63.104(h) and (i) re-monitoring at the monitoring location where a leak is identified to ensure that any leaks found are fixed. Finally, we proposed that none of these requirements would apply to heat exchange systems that have a maximum cooling water flow rate of 10 gallons per minute or less.

A requirement at 40 CFR 63.524(a)(3) and (b)(3) that owners and operators of existing, new, or reconstructed affected WSR sources subject to the P&R II NESHAP comply with both the equipment leak standards in the HON and the HAP emissions limitation for process vents, storage tanks, and wastewater systems ( i.e., we proposed that the alternative standard is no longer optional). For the P&R II NESHAP, we also proposed to include valves in the definition of “equipment leaks” at 40 CFR 63.522 such that owners and operators of an existing, new, or reconstructed affected BLR or WSR source would be required to comply with the same LDAR program that already exists in the HON and the P&R I NESHAP for valves that contain or contact material that is 5 percent by weight or more of organic HAP, operate 300 hours per year or more, and are not in vacuum service.

A requirement at 40 CFR 63.119(b)(7), that owners and operators that use a sweep, purge, or inert blanket between the IFR and fixed roof of a storage vessel would be required to route emissions through a closed vent system and control device.

We proposed that all of these requirements (proposed for the purpose of addressing regulatory gaps) are consistent with CAA section 112(d) controls and reflect the MACT floor, and we did not identify any additional options beyond these ( i.e., beyond-the-floor options) for controlling emissions from these emission sources. More information concerning our proposed requirements under CAA section 112(d)(2) and (3) and 112(h) can be found in sections III.D and III.E of the proposal preamble (88 FR 25080, April 25, 2023).

2. How did the revisions pursuant to CAA section 112(d)(2) and (3) and 112(h) change since proposal?

The EPA is finalizing the work practice standard for storage vessel degassing, as proposed, except that we are adding an option at 40 CFR 63.119(a)(6) to allow owners and operators to degas a storage vessel to the atmosphere once a vapor space organic HAP concentration of less than 5,000 ppmv as methane is met (in lieu of having to meet a vapor space concentration threshold of less than 10 percent of the LEL). We are also correcting our use of the term “LEL” versus our use of the term “concentration” in 40 CFR 63.119(a)(6) in that “the concentration” of the vapors in storage vessels be less than 10 percent of the LEL and that owners and operators are required to measure “the concentration” of the vapors as a percent of the LEL. We are also revising the final rule at 40 CFR 63.119(a)(6) to include storage vessels in EtO service subject to 40 CFR 63.119(a)(5).

The EPA is finalizing the revisions to the work practice standard for planned routine maintenance of storage vessels, as proposed, except that we are clarifying in the final rule at 40 CFR 63.119(f)(3) that the 240-hour planned routine maintenance provisions also apply for breathing losses for fixed rood roof vessels routed to a fuel gas system or to a process.

The EPA is finalizing the requirements for pressure vessels, as proposed, except that we are: (1) Clarifying that the pressure vessel requirements at 40 CFR 63.119(a)(7) only apply to pressure vessels that are considered Group 1 storage vessels; (2) clarifying that if the equipment is not a connector, gas/vapor or light liquid valve, light liquid pump, or PRD in EtO service and the equipment is on a pressure vessel located at a HON or P&R I facility, then that particular equipment is not subject to HON subpart H, but rather the equipment is subject to the pressure vessel requirements we proposed and are finalizing in 40 CFR 63.119(a)(7); (3) clarifying that unsafe and difficult/inaccessible to monitor provisions in 40 CFR 63.168(h) and (i) (for valves in gas/vapor service and in light liquid service) and in 40 CFR 63.174(f) and (h) (for connectors in gas/vapor service and in light liquid service) still apply to valves and connectors when complying with 40 CFR 63.119(a)(7); and (4) replacing the word “deviation” with “violation” in the final rule text at 40 CFR 63.119(a)(7).

The EPA is finalizing the requirements for surge control vessels and bottoms receivers, as proposed, except that we are adding language in the “C” and “Q” terms of the equations at 40 CFR 63.115(g)(3)(ii) and (g)(4)(iv) to allow the use of engineering calculations to determine concentration or flow rate only in situations where measurements cannot be taken with EPA reference methods. We are also adding reference methods for measuring flow rate at 40 CFR 63.115(g)(3)(ii) and 40 CFR 63.115(g)(4)(iv).

Also, we are clarifying in the final rule that the requirements for sweep, purge, and inert blankets from IFRs at 40 CFR 63.119(b)(7) applies only if a continuous sweep, purge, or inert blanket is used between the IFR and fixed roof that causes a pressure/vacuum vent to remain continuously open to the atmosphere where uncontrolled emissions are greater than or equal to 1.0 lb/hr of total organic HAP.

3. What key comments did we receive on the proposal revisions pursuant to CAA section 112(d)(2) and (3) and 112(h), and what are our responses?

This section provides summaries of and responses to the key comments received regarding our proposed revisions for periods of SSM, including maintenance vents and equipment openings, storage vessel degassing, planned routine maintenance of storage vessels, pressure vessels, surge control vessels and bottoms receivers, and the requirements for sweep, purge, and inert blankets from IFRs. Other comment summaries and the EPA's responses for additional issues raised regarding these activities, as well as issues raised regarding our proposed revisions for flares, PRDs, bypass lines on closed vent systems, emission limits for dioxins and furans, transfer operations (for HON), heat exchange systems (for the P&R II NESHAP), and equipment leaks (for the P&R II NESHAP) can be found in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

a. Maintenance Vents

Comment: Commenters contended that the EPA misuses the term LEL for the maintenance vents and storage vessel degassing provisions. A commenter said that the regulatory language implies that operators have the ability to change the LEL of a vapor by purging or otherwise removing portions of the vapor from equipment. This commenter said that the concentration of a flammable gas or mixture can be lowered ( e.g., by dilution or displacement) to a level that is less than the LEL; thus, they requested that the EPA clarify that concentration of the vapors in equipment be less than 10 percent of the LEL and that facilities are to measure the vapor concentration, not the LEL. Similarly, another commenter requested that the EPA clarify that the concentration of the vapors in equipment and storage vessels be less than 10 percent of the LEL and that facilities are to measure the concentration of the vapors as a percent of the LEL ( i.e., with a hand-held analyzer that reports concentration as a percent of LEL, and not the LEL itself). The commenter suggested that these changes should be made to 40 CFR 63.113(k), 40 CFR 63.118(f) and (m), 40 CFR 63.119(a)(6), 40 CFR 63.486(i), 40 CFR 63.491(h), and 40 CFR 63.492(g). The commenter provided an example saying that in proposed 40 CFR 63.119(a)(6), the second instance of “LEL” should be corrected to read “The owner or operator must determine the concentration using process instrumentation or portable measurement devices . . .”.

Response: We agree with the commenters that our proposed use of the term LEL improperly implies that operators have the ability to change the LEL of a vapor by purging or otherwise removing portions of the vapor from equipment. In the final rule, we are revising 40 CFR 63.113(k)(1)(i) and (ii) and (k)(2), 40 CFR 63.119(a)(6), 40 CFR 63.118(f)(9)(iii) and (m)(2), (3), and (5), 40 CFR 63.486(i)(1)(i) and (ii) and (i)(2), 40 CFR 63.491(h)(2), (3), and (5), and 40 CFR 63.492(g)(3) to clarify that “the concentration” of the vapors in equipment and storage vessels be less than 10 percent of the LEL and that facilities are to measure “the concentration” of the vapors as a percent of the LEL.

b. Storage Vessel Degassing

Comment: Several commenters supported the proposed degassing provisions at 40 CFR 63.119(a)(6). However, some commenters requested the EPA also add a concentration limit as an alternative to LEL measurements. The commenters explained that some nonflammable chemicals do not exhibit an LEL, or through the use of an inert blanket, the storage vessel atmosphere would not have an LEL, so owners and operators of storage vessels under these conditions would be unable to comply with the proposed 10 percent LEL threshold. These commenters requested that the EPA allow the storage vessel to be opened after the vapor space organic HAP content has been reduced below 5,000 ppmv, based on the Agency's assertion that this level is equivalent to 10 percent of the LEL. A commenter pointed out that 5,000 ppmv as methane equals 10 percent of the LEL for methane.

Response: We agree with commenters that some nonflammable chemicals do not exhibit an LEL, or through the use of an inert blanket, the storage vessel atmosphere would not have an LEL, so owners and operators of storage vessels under these conditions would be unable to comply with the proposed 10 percent LEL threshold. Therefore, we are revising the final rule at 40 CFR 63.119(a)(6) to allow storage vessels to be vented to the atmosphere once a storage vessel degassing organic HAP concentration of 5,000 ppmv as methane is met, or until the vapor space concentration is less than 10 percent of the LEL. We stated in the preamble to the proposed rule (88 FR 25080, April 25, 2023) that we are aware of three regulations regarding storage vessel degassing, two in the state of Texas and the third for the South Coast Air Quality Management District (SCAQMD) in California. Texas has degassing provisions in the TAC and through permit conditions, while Rule 1149 contains the SCAQMD degassing provisions. The TAC requirements are the least stringent and require control of degassing emissions until the vapor space concentration is less than 35,000 ppmv as methane or 50 percent of the LEL. The Texas permit conditions require control of degassing emissions until the vapor space concentration is less than 10 percent of the LEL or until the VOC concentration is less than 10,000 ppmv, and SCAQMD Rule 1149 requires control of degassing emissions until the vapor space concentration is less than 5,000 ppmv as methane. The Texas permit conditions requiring compliance with 10 percent of the LEL and SCAQMD Rule 1149 control requirements are considered equivalent because 5,000 ppmv as methane equals 10 percent of the LEL for methane.

Comment: A commenter remarked that the work practice standard proposed in 40 CFR 63.119(a)(6) should not only apply to degassing Group 1 storage vessels, but should also be applicable for degassing storage vessels in EtO service. The commenter explained that a storage vessel in EtO service (subject to 40 CFR 63.119(a)(5)) may also need to be degassed during storage vessel shutdown operations, but the way the proposed language is currently written, the storage vessel degassing provisions only apply to storage vessels subject to 40 CFR 63.119(a)(1) and (a)(2). The commenter requested the EPA amend the language in 40 CFR 63.119(a)(6) to include storage vessels in EtO service subject to 40 CFR 63.119(a)(5).

Response: It was not our intent to exclude storage vessels in EtO service from the work practice standard in 40 CFR 63.119(a)(6); therefore, we are revising the final rule at 40 CFR 63.119(a)(6) to include storage vessels in EtO service subject to 40 CFR 63.119(a)(5). However, owners and operators are still prohibited from releasing more than 1.0 ton of EtO from all maintenance vents combined in any consecutive 12-month period at 40 CFR 63.113(k)(4). In other words, we still consider degassing a storage vessel a type of maintenance vent. As stated in the final rule (as proposed), an owner or operator may designate any vent stream as a maintenance vent if the vent is only used as a result of startup, shutdown, maintenance, or inspection of equipment where equipment is emptied, depressurized, degassed, or placed into service.

c. Planned Routine Maintenance for Storage Vessels

Comment: A commenter said they supported the proposed work practice standard for periods of planned routine maintenance for storage vessels including the proposed requirement that owners and operators would not be permitted to fill storage vessels during these periods. However, another commenter pointed out that the 240-hour planned routine maintenance provisions at 40 CFR 63.119(f)(3) (for fixed rood roof vessels routed to a fuel gas system or to a process) is inconsistent with the parallel requirement at 40 CFR 63.119(e)(7) for fixed rood roof vessels routed to a control device. The commenter requested the EPA make 40 CFR 63.119(f)(3)(iii) no longer apply on or after the compliance dates specified in 40 CFR 63.100(k)(10) and allow for, in a new paragraph at 40 CFR 63.119(f)(3)(iv), the 240-hour planned routine maintenance provisions for breathing losses for fixed rood roof vessels routed to a fuel gas system or to a process. Citing page 25161 of the preamble to the proposed rule (88 FR 25080, April 25, 2023), the commenter contended that this recommended change for fixed rood roof vessels routed to a fuel gas system or to a process would be consistent with the proposed rule text at 40 CFR 63.119(e)(7) for fixed rood roof vessels routed to a control device. The commenter added that their recommendation is also similar to the approach that the EPA used in the Organic Liquids Distribution MACT (NESHAP subpart EEEE) under 40 CFR 63.2378(d) and (e)(4). The commenter pointed out that the associated recordkeeping requirement in 40 CFR 63.123(h) would also need to be amended slightly to reference the new recommended paragraph at 40 CFR 63.119(f)(3)(iv).

Response: We agree with the commenter that the 240-hour planned routine maintenance provisions should apply for breathing losses for fixed rood roof vessels routed to a fuel gas system or to a process given this would parallel the requirement at 40 CFR 63.119(e)(7). Therefore, we are revising the final rule to sunset 40 CFR 63.119(f)(3)(iii) in accordance with the schedule specified in 40 CFR 63.100(k)(10), and to include a new paragraph at § 63.119(f)(3)(iv). We are also revising the final rule at 40 CFR 63.123(h)(3) to reference “§ 63.119(f)(3)(iv)” instead of “§ 63.119(f)(3)(iii).” Additionally, we are revising 40 CFR 63.100(k)(10) to reference “§ 63.119(f)(3)(iv)” as well as the introductory text in 40 CFR 63.119(f)(3) to properly reference the new paragraph at “§ 63.119(f)(3)(iv).” The new paragraph at 40 CFR 63.119(f)(3)(iv) reads: “For each source as defined in § 63.101, beginning no later than the compliance dates specified in § 63.100(k)(10), paragraph (f)(3)(iii) of this section no longer applies. Instead, if you elect to route emissions from storage vessels to a fuel gas system or to a process to comply with the requirements of paragraph (a)(1), (a)(2), or (a)(5) of this section, the fuel gas system or process may only be bypassed when the planned routine maintenance cannot be performed during periods that storage vessel emissions are vented to the fuel gas system or process, and the total aggregate amount of time during which the breathing loss emissions bypass the fuel gas system or process during the calendar year without being routed to a control device must not exceed 240 hours. The level of material in the storage vessel shall not be increased during periods that the fuel gas system or process is bypassed to perform routine maintenance.”

d. Pressure Vessels

Comment: Some commenters requested that the EPA clarify what is meant by the requirement to monitor “each point on a pressure vessel at § 63.119(a)(7)(ii).” These commenters contested that components such as valves, pumps, and flanges servicing a pressure vessel and that are already subject to LDAR program requirements should be excluded from these provisions.

A commenter added that PRDs associated with pressure vessels should be eligible to comply with the EPA's proposed PRD work practice standards in 40 CFR 63.165(e) and a release of total organic HAP to the atmosphere through a pressure vessel's PRD should not be considered a deviation per 40 CFR 63.119(a)(7)(v). The commenter explained that PRDs associated with larger pressure vessels, such a pressure sphere, are typically designed for very rare scenarios like a fire protection case, and thus venting flammable vapors vertically upward to the atmosphere is a safety feature. The commenter said that many engineering design issues will need to be evaluated before routing PRDs associated with specific pressure vessels to a collection system and control device, such as the potential for back-pressure on the collection header if multiple pressure vessels are included, and the potential for rapidly changing pressures and temperatures that may warrant special designs for the collection header and emission control equipment.

Response: It was our intent that if the equipment is not a connector, gas/vapor or light liquid valve, light liquid pump, or PRD in EtO service and the equipment is on a pressure vessel located at a HON or P&R I facility, then that particular equipment is not subject to HON subpart H, but rather the equipment is subject to the pressure vessel requirements we proposed and are finalizing in 40 CFR 63.119(a)(7). Connectors, gas/vapor or light liquid valves, light liquid pumps, and PRDs in EtO service located on a pressure vessel at a HON facility are still subject to HON subpart H; and we are clarifying this in the final rule at 40 CFR 63.119(a)(7). As we stated in the preamble to the proposed rule (88 FR 25080, April 25, 2023), the LDAR requirements at 40 CFR 63.119(a)(7) (for HON) and 40 CFR 63.484(t) (for the P&R I NESHAP) are based on similar no-detectable emission requirements required for closed vent systems in most chemical sector NESHAP. The intent of this language is to impose a standard that requires no detectable emissions at all times ( i.e., would be required to meet a leak definition of 500 ppm at each point on the pressure vessel where total organic HAP could potentially be emitted); require initial and annual leak monitoring using EPA Method 21; and require routing organic HAP through a closed vent system to a control device ( i.e., no releases to the atmosphere through a pressure vessel's PRD). Most pressure vessels have relief devices that allow for venting when pressure exceeds setpoints. There are also instances where other components in pressure systems may allow for fugitive releases because of leaks from fittings or cooling systems.

We note that our use of the term “deviation” in the preamble to the proposed rule and in 40 CFR 63.119(a)(7) was an error. While the MON rule text uses the MON-defined term “deviation” to describe emissions events, the current HON rule text uses the term “violation.” There are no uses of the term “deviation” to describe an emissions event in the current HON rule text, nor any definition of that term in the HON. Therefore, given that we are building off the existing HON standards, we believe it is more appropriate to continue to use the term “violation” (in lieu of the undefined term “deviation”) in all of the HON rule text. We have replaced “deviation” with “violation” in the final rule text at 40 CFR 63.119(a)(7).

Comment: Some commenters contended that the pressure vessel monitoring provisions in 40 CFR 63.119(a)(7) are not feasible for some tanks because the pressure vessel is not accessible to monitoring personnel. The commenter explained that some pressure vessels that store regulated chemicals are located inside containment areas or are partially buried such that monitoring of the vessel surface per EPA Method 21 is not possible. The commenter added that some pressure vessels are double walled tanks designed such that there is an additional external shell outside of the pressure vessel shell ( i.e., a tank within a tank shell). The commenter suggested: (1) Pressure monitoring of the gas space (typically nitrogen) between the pressure vessel wall and the second exterior wall be conducted to detect a potential leak, and if a pressure increase occurs, then the owner or operator should be allowed to follow a work practice that requires that the leak be repaired as soon as practical; and (2) for situations where a pressure vessel is located inside a containment area or partially buried, the owner or operator should only be required to conduct EPA Method 21 monitoring on potential leak sources that are accessible and are not unsafe-to-monitor. The commenter provided suggested rule text edits in order to accommodate this request. Similarly, another commenter suggested the EPA incorporate “unsafe-to-monitor” and “inaccessible” provisions at 40 CFR 63.119(a)(7) similar to those in other sections of NESHAP subpart H and in NESHAP subpart UU because some pressure vessels are located in concrete containment areas, are partially buried, or are otherwise inaccessible for safety purposes. This commenter pointed out that the EPA did not consider costs for facilities to relocate or install new pressure vessels to make them accessible in order to comply with the proposed requirements.

Response: It was our intent that unsafe and difficult/inaccessible to monitor provisions in 40 CFR 63.168(h) and (i) (for valves in gas/vapor service and in light liquid service) and in 40 CFR 63.174(f) and (h) (for connectors in gas/vapor service and in light liquid service) still apply to valves and connectors when complying with 40 CFR 63.119(a)(7). We are clarifying this in the final rule at 40 CFR 63.119(a)(7)(ii).

Comment: A commenter pointed out that the proposed pressure vessel requirements in 40 CFR 63.119(a)(7) appear to apply to any pressure vessel to which NESHAP subpart G applies. The commenter argued that these requirements should only apply to Group 1 storage vessels that are pressure vessels. The commenter explained that with the removal of the pressure vessel exclusion from the storage vessel definition in 40 CFR 63.101 and the addition of the pressure vessel requirements in 40 CFR 63.119(a)(7), the EPA may have inadvertently applied the proposed pressure vessel requirements to all pressure vessels, regardless of whether the pressure vessel is Group 1 or Group 2 or whether the storage vessel is exempt for another reason. The commenter contended that there is no reason that a Group 2 storage vessel ( i.e., one not requiring control) or any other vessel that meets an exclusion in the storage vessel definition should be subject to the proposed operating standards for pressure vessels in 40 CFR 63.119(a)(7).

Response: We agree with the commenter that 40 CFR 63.119(a)(7) should only apply to pressure vessels that are considered Group 1 storage vessels (as defined in Table 5 to NESHAP subpart G for existing sources and Table 6 to NESHAP subpart G for new sources). Given that we removed the exemption for “pressure vessels designed to operate in excess of 204.9 kilopascals and without emissions to the atmosphere” from the definition of storage vessel in the final rule, all pressure vessels (not just pressure vessels operating less than or equal to 204.9 kilopascals) are now considered storage vessels in the HON. For this reason, we are clarifying in the final rule that “for each pressure vessel as defined in § 63.101 that is considered a Group 1 storage vessel (as defined in Table 5 of this subpart for existing sources and Table 6 of the subpart for new sources), you must operate and maintain the pressure vessel” as specified in paragraphs 40 CFR 63.119(a)(7)(i) through (v).

e. Surge Control Vessels and Bottoms Receivers

Comment: A commenter requested that the EPA clarify whether the proposed threshold criteria for controlling surge control vessels and bottoms receivers ( i.e., the 1.0 lb/hr total organic HAP threshold) is on an annual average basis or based on any intermittent emissions that exceed the 1.0 lb/hr emission standard.

Response: As we stated in the preamble to the proposed rule (88 FR 25080, April 25, 2023), emissions from surge control vessels and bottoms receivers are characteristic of process vents, not emissions from storage vessels. Our rationale for making this determination is that these vessels operate at process temperatures, not ambient storage temperatures; typically do not undergo level changes that larger storage vessels undergo; and are most often operated under pressure with and without non-condensable gases flowing into and out of them. The size of these vessels is also typically not correlated with emissions, as are storage vessels. The 1.0 lb/hr total organic HAP threshold is based on any continuous emissions that exceed the 1.0 lb/hr emission standard. This is true for all Group 1 process vents. We are finalizing this threshold as proposed given that we found this threshold to be cost-effective for process vents (see our response to comments in section IV.B.3.a.i of this preamble for further details).

Comment: A commenter requested that the EPA provide the option to use engineering calculations if measurements cannot be made using EPA reference methods to determine whether surge control vessels and bottoms receivers are required to be controlled. The commenter said that the vents from surge control vessels and bottoms receivers are configured more like small tanks than process vents and that these vents could be configured in a variety of ways. The commenter provided an example where the vent may be configured as a pressure/vacuum vent for which venting occurs on an intermittent basis, making it difficult to measure volumetric flow rate since the measurements are not made from a straight discharge pipe where the flow measurement device ( e.g., a pitot tube) can be inserted.

Response: The EPA agrees with the commenter that in certain situations, as a result of how surge vessels and bottoms receivers are configured, taking measurements utilizing EPA reference methods may not be possible. As a result, we are finalizing language in the “C” and “Q” terms of the equations at 40 CFR 63.115(g)(3)(ii) and (g)(4)(iv) allowing the use of engineering calculations to determine concentration or flow rate only in situations where measurements cannot be taken with EPA reference methods. We anticipate that in most situations, as evidenced by one facility's responses to the CAA section 114 request, facilities will be able to take measurements from surge vessels and bottoms receivers as if they were process vents. In addition, the EPA notes that while the commenter expressed concern about measuring flow rate, the proposed reference methods (EPA Method 25A or EPA Method 18) are utilized to measure concentration. Given it was the EPA's intent to provide methodology for measuring both flow rate and concentration as part of the proposal, we are adding reference methods for measuring flow rate at 40 CFR 63.115(g)(3)(ii) and 40 CFR 63.115(g)(4)(iv) by adding the following text to the definition of, Q, the flow rate term to remedy the lack of clarity: “determined using Method 2, 2A, 2C, or 2D of 40 CFR part 60, appendix A, as appropriate.”

f. Control of Sweep, Purge, and Inert Blankets From IFRs

Comment: Several commenters objected to the proposed requirements at 40 CFR 63.119(b)(7) that would require owners and operators that use sweep, purge, or inert blankets between the IFR and fixed roof of storage vessels to route emissions through a closed vent system and control device. Some commenters explained that the EPA did not consider the cost-effectiveness of controls under CAA section 112(d)(2) when considering this proposal. A commenter said that most IFR storage vessels are equipped with a sweep, purge, or blanket and the proposed requirements would render these storage vessels obsolete, given that facilities could remove the IFR and route all emissions to a control device while remaining in compliance with the rule. The commenter acknowledged that a continuous purge of an inert blanket will result in higher emissions from an IFR than no purge; however, the commenter added that IFR storage vessels are normally not designed to hold pressure, and the space between the IFR and the fixed roof must vent somewhere when the vessel is being filled, and conversely there must be a mechanism to avoid a vacuum in the vessel when the vessel is being emptied to prevent a vessel failure. To support their objection to the proposed requirements at 40 CFR 63.119(b)(7), the commenter provided a cost analysis for this level of control that resulted in emissions reductions of 0.1 lb/hr of HAP per vessel, which they estimated would cost $190,000/yr to control and would not be cost-effective. Other commenters agreed with this cost analysis and stated the cost would not justify the additional amount of emissions reductions. These commenters suggested the EPA revise their analysis, and if the proposed level of control was found to be cost-effective, the commenters requested that the EPA also consider the secondary emissions ( i.e., CO, NO_X, and CO₂) that would result from the additional fuel required to treat a stream largely comprised of inert gas. A commenter said that adding downstream abatement measures to IFR vessels will require significant structural foundations to and from, or between, as applicable, emission sources, air abatement controls, utilities, and control systems for tanks already located at relatively remote locations, making them more costly than otherwise similar ancillary equipment at locations closer to manufacturing operations. Finally, the commenter requested that the EPA clarify whether the proposed requirements apply to all vessels with a sweep, purge, or blanket, or only a subset, as vessels with IFRs are generally not designed to hold pressure, and would need to vent to avoid negative pressure. The commenter added that the space between the IFR and the fixed roof must vent somewhere when the vessel is being filled and conversely there must be a mechanism to avoid a vacuum in the tank when the vessel is being emptied to prevent a tank failure.

Response: Installing a floating roof minimizes evaporative losses of the stored liquid. Both contact and noncontact decks incorporate rim seals and deck fittings to reduce evaporative loss of the stored liquid. Evaporative losses from floating roofs may come from deck fittings, nonwelded deck seams, and the annular space between the deck and vessel wall. In addition, IFRs are freely vented by circulation vents at the top of the fixed roof. The vents minimize the possibility of organic vapor accumulation in the tank vapor space in concentrations approaching the flammable range. An IFR vessel not freely vented is considered an IFR vessel with a closed vent system. Sections 7.1.3 and 7.1.3.8.2 of EPA's AP-42, Fifth Edition, provide emission estimation methods for freely vented IFR vessels and IFR vessels vented only through a pressure/vacuum vent in the fixed roof ( i.e., no open vents), respectively.

The HON allows owners or operators to choose from different options to control emissions from storage vessels and comply with the MACT standards ( i.e., owners and operators can use a closed vent system and control device to reduce inlet emissions of total organic HAP by 95 percent or greater, or reduce organic HAP by utilizing a fixed roof and IFR, an EFR, an EFR converted to an IFR, route the emissions to a process or a fuel gas system, or vapor balance). As such, the use of a floating roof that meets the requirements in 40 CFR 63.119(b) is one of the control options owners or operators may choose for control of emissions during normal storage vessel operations.

Section 7.1 of the EPA's AP-42, Fifth Edition suggests a default reduction of 5 percent on total estimated emissions to account for the use of closed vents on an IFR. This recommendation is based on API Technical Report 2569 which we have determined assumes gas blanketing or another method is used (for IFR vessels vented only through a pressure/vacuum vent in the fixed roof) to prevent the development of a combustible gas mixture within the vessel. However, we believe that neither AP-42 or API Technical Report 2569 addresses the scenario where the use of a sweep, purge, or inert blanket between the IFR and fixed roof would cause a pressure/vacuum vent to remain continuously open to the atmosphere; and this scenario was certainly not considered during the development of the HON MACT standard for storage vessels. A pressure/vacuum vent that remains continuously open to the atmosphere while using a sweep, purge, or inert blanket between the IFR and fixed roof is effectively a continuous process vent.

We note that in a 2021 site-specific monitoring plan submitted to the EPA for approval for fenceline monitoring at a refinery located in Corpus Christi, Texas (see Site-Specific Benzene Fenceline Monitoring Plan Corpus Christi Refinery East Plant Revision 2, CITGO Petroleum Corporation, December 1, 2021, which is available in the docket for this rulemaking), the company identified a slow rise in benzene concentration over the course of about a year. During this period, the company said they investigated the area for potential sources of the elevated benzene concentrations and completed a root cause analysis that identified a HON IFR storage vessel as the primary cause. The particular HON IFR storage vessel uses a nitrogen blanket between the IFR and the fixed roof to protect the storage contents from being contaminated with oxygen. During the investigation, the company found that the nitrogen regulator was malfunctioning which increased the pressure within the tank and ultimately released emissions to the atmosphere (due to a small operating set point range for the nitrogen regulator and relief vent). Ultimately, the company addressed the elevated benzene concentrations by replacing the nitrogen regulator on the HON IFR storage vessel and routing the emissions to a liquid scrubber, carbon absorption system, and a vapor combustion unit. We have also seen other companies acknowledge similar fenceline monitoring scenarios where HON IFR storage vessels (with sweep, purge, or inert blanket between the IFR and the fixed roof of the vessel) are contributing to elevated benzene concentrations (see Site Specific Monitoring Plan, ExxonMobil Baton Rouge Refinery, September 27, 2019, which is available in the docket for this rulemaking).

As such, we believe the use of a sweep, purge, or inert blanket between the IFR and fixed roof that would cause a pressure/vacuum vent to remain continuously open to the atmosphere is a regulatory gap. Given that continuous sweeping, purging, or blanketing between the IFR and the fixed roof of the vessel effectively creates a continuous process vent, we proposed to address this regulatory gap pursuant to CAA section 112(d)(2) and (3), by requiring owners and operators that use a sweep, purge, or inert blanket between the IFR and fixed roof of a storage vessel to route emissions through a closed vent system and control device (see 40 CFR 63.119(b)(7)). In light of the comments received, we are clarifying in the final rule at 40 CFR 63.119(b)(7) that owners and operators must route emissions through a closed vent system and control device if they use a continuous sweep, purge, or inert blanket between the IFR and fixed roof that causes a pressure/vacuum vent to remain continuously open to the atmosphere where uncontrolled emissions are greater than or equal to 1.0 lb/hr of total organic HAP. This threshold is consistent with the definition we proposed and are finalizing for Group 1 process vents. These requirements are consistent with CAA section 112(d) controls and reflect the MACT floor. With regard to cost, the MACT floor is the minimum control level allowed for MACT standards promulgated under CAA section 112(d)(3), not CAA section 112(d)(2), and may not be based on cost considerations.

4. What is the rationale for our final approach and final decisions for the revisions pursuant to CAA section 112(d)(2) and (3)?

We evaluated all of the comments on the EPA's proposed amendments to revisions for flares used as APCDs, clarifications for periods of SSM and bypasses, including PRDs, bypass lines on closed vent systems, and planned routine maintenance of storage vessels, and requirements for maintenance vents and equipment openings, storage vessel degassing, emission limits for dioxins and furans, pressure vessels, surge control vessels and bottoms receivers, sweep, purge, and inert blankets from IFRs, transfer operations (for HON), heat exchange systems (for the P&R II NESHAP), and equipment leaks (for the P&R II NESHAP). For the reasons explained in section III.D of the proposal preamble (88 FR 25080, April 25, 2023), we find that the flare amendments are needed to ensure that flares used as APCDs achieve the required level of MACT control and meet 98-percent destruction efficiency at all times as well as to ensure that CAA section 112 standards apply at all times. Similarly, the clarifications for periods of SSM and bypasses, including PRDs, bypass lines on closed vent systems, and planned routine maintenance of storage vessels, and requirements for maintenance vents and equipment openings, storage vessel degassing, emission limits for dioxins and furans, pressure vessels, surge control vessels and bottoms receivers, sweep, purge, and inert blankets from IFRs, transfer operations (for HON), heat exchange systems (for the P&R II NESHAP), and equipment leaks (for the P&R II NESHAP) are needed to be consistent with Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008) to ensure that CAA section 112 standards apply at all times. More information and rationale concerning all the amendments we are finalizing pursuant to CAA sections 112(d)(2) and (3) is in the preamble to the proposed rule (88 FR 25080, April 25, 2023), in section IV.C.3 of this preamble, and in the comments and our specific responses to the comments in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking. Therefore, we are finalizing the proposed provisions for flares, finalizing the proposed clarifications for periods of SSM and bypasses, including PRD releases, bypass lines on closed vent systems, and planned routine maintenance of storage vessels, and finalizing standards for maintenance vents and equipment openings, storage vessel degassing, emission limits for dioxins and furans, pressure vessels, surge control vessels and bottoms receivers, sweep, purge, and inert blankets from IFRs, transfer operations (for HON), heat exchange systems (for the P&R II NESHAP), and equipment leaks (for the P&R II NESHAP).

D. Amendments Addressing Emissions During Periods of SSM

1. What amendments did we propose to address emissions during periods of SSM?

We proposed amendments to the HON and the P&R I and P&R II NESHAP to remove and revise provisions related to startup, shutdown, and maintenance (SSM) that are not consistent with the requirement that the standards apply at all times. In a few instances, we are finalizing alternative standards for certain emission points ( i.e., emergency flaring, PRDs, maintenance activities, and tank degassing) to minimize emissions during periods of SSM to ensure a continuous CAA section 112 standard applies “at all times” (see section IV.C of this preamble); however for the majority of emission points in the SOCMI, P&R I, and P&R II source categories, we proposed eliminating the SSM exemptions and to have the emission standards apply at all times. We note that on April 21, 2011 (see 77 FR 22566), the EPA finalized amendments to eliminate the SSM exemption in the P&R I NESHAP; however, for consistency with the SSM related amendments that we proposed for the HON and P&R II NESHAP, we also proposed additional amendments to the P&R I NESHAP related to the SSM exemption that were not addressed in the April 21, 2011, P&R I rule. More information concerning the elimination of SSM provisions is in section III.E.1 of the proposal preamble (88 FR 25080, April 25, 2023).

We also proposed to remove the affirmative defense provisions at 40 CFR 63.480(j)(4) (for the P&R I NESHAP) to comply with the holding in NRDC v. EPA, 749 F.3d 1055 (D.C. Cir., 2014). More information concerning the removal of the affirmative defense provisions is in section III.E.2 of the proposal preamble (88 FR 25080, April 25, 2023).

We proposed standards in the NSPS subparts VVb, IIIa, NNNa, and RRRa that apply at all times. For NSPS VVb, we proposed that the work practice standards will apply at all times, including during SSM. For NSPS subparts IIIa, NNNa, and RRRa, we proposed performance standards and work practice standards that will apply during periods of startup and shutdown (including when maintenance and inspection activities are being conducted). Although the NSPS general provisions in 40 CFR 60.8(c) contain an exemption from non-opacity standards, we proposed in NSPS subparts IIIa, NNNa, and RRRa specific requirements at 40 CFR 40 CFR 60.612a, 40 CFR 60.662a, and 40 CFR 60.702a, respectively, that override the general provisions for SSM. Accordingly, we proposed NSPS subparts VVb, IIIa, NNNa, and RRRa would include standards that apply at all times, including during periods of startup and shutdown.

2. How did the SSM provisions change since proposal?

We are finalizing the SSM provisions as proposed. We are also finalizing, as proposed, the removal of the provisions to assert an affirmative defense to civil penalties in the P&R I NESHAP at 40 CFR 63.480(j)(4). See 88 FR 25080, April 25, 2023.

3. What key comments did we receive on the SSM revisions and what are our responses?

To ensure a continuous CAA section 112 standard applies “at all times” (see section IV.C of this preamble), we are finalizing, as proposed, the elimination of the SSM exemptions for the SOCMI, P&R I, and P&R II source categories. To ensure a continuous CAA section 111 standard applies “at all times,” we are finalizing, as proposed, the requirement that the standards in NSPS subparts VVb, IIIa, NNNa, and RRRa “apply at all times, including periods of startup, shutdown and malfunction.” We are also finalizing some alternative standards in this final rule for certain emission points during periods of SSM. This section provides summaries of and responses to the key comments received regarding our proposed requirements for PRDs at 40 CFR 63.165(e)(3)(v)(B) and (C) and smoking flares at 40 CFR 63.670(o)(7)(ii) and (iv) during malfunctions. Other comment summaries and the EPA's responses for additional issues raised regarding other SSM issues raised regarding our proposed revisions can be found in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

Comment: Several commenters generally supported removal of the SSM exemptions in the rules given it is consistent with Sierra Club v. EPA, 551 F.3d 1019, 1028 (D.C. Cir. 2008). A commenter said that they agreed with the approach the EPA has taken to amend language throughout the HON to indicate which paragraphs or phrases no longer apply as a result of the proposed SSM revisions.

Other commenters suggested that the EPA also close proposed loopholes for releases from PRDs at 40 CFR 63.165(e)(3)(v)(B) and (C) and smoking flares at 40 CFR 63.670(o)(7)(ii) and (iv) during malfunctions. Some of these commenters said that according to facilities' self-reported data, SSM emissions are often of the same magnitude as the facilities' reported routine emissions, and SSM emissions tend to spike during severe weather events. A commenter pointed out specific reportable quantities of emissions resulting from unplanned emissions events and planned SSM activities via the State of Texas Environmental Electronic Reporting System (STEERS). The commenters argued that with the properly installed and executed emission control systems, fail safes, backup power, maintenance procedures and risk management plans, emissions associated with both extreme weather and routine operations are preventable and should not be exempted from legally permitted emission limits. The commenters argued that the EPA erroneously concludes that the malfunction loopholes at 40 CFR 63.165(e)(3)(v)(B) and (C) and smoking flares at 40 CFR 63.670(o)(7)(ii) and (iv) are reasonable.

Commenters contended that these malfunction loopholes have real-world, harmful effects on the health of communities surrounding these facilities. The commenters pointed out that the EPA readily admits, “[p]ressure relief events from PRDs that vent to the atmosphere have the potential to emit large quantities of HAPs” and the EPA also noted that the majority of the Indorama Port Neches Plant's excess cancer risk is “driven by EtO emissions from PRDs (74 percent).” A commenter added that the EPA similarly found a “high potential risk posed by chloroprene from PRD releases.” The commenter also argued that:

• the PRD and smoking flare loopholes (at40 CFR 63.165(e)(3)(v)(B) and (C) and 40 CFR 63.670(o)(7)(ii) and (iv)) are just another variation on the original malfunction exemption and the affirmative defense to civil penalties, each of which the D.C. Circuit has found unlawful under CAA sections 302(k), 304, 113, 112(d), and 112(f).
• the EPA's creation of these exemptions (at40 CFR 63.165(e)(3)(v)(B) and (C) and 40 CFR 63.670(o)(7)(ii) and (iv)) runs directly contrary to its own recognition in prior administrative practice citing the EPA's brief defending the boiler rule.
• even though the EPA included reporting and root cause analysis requirements, the work practice standards still constitute a total exemption from the core requirements for PRDs and flares during malfunctions of unlimited HAP release in amount and duration (in other words, there is no limit on the amount of HAPs emitted that applies during those releases allowed at40 CFR 63.165(e)(3)(v)(B) and (C) and 40 CFR 63.670(o)(7)(ii) and (iv)); and the EPA attempted to justify its original SSM exemption on similar grounds in Sierra Club v. EPA, 551 F.3d 1019, 1028 (D.C. Cir. 2008), stating that reporting and other requirements still applied, but that argument failed.
• the PRD and flare loopholes (at40 CFR 63.165(e)(3)(v)(B) and (C) and 40 CFR 63.670(o)(7)(ii) and (iv)) are not lawful work practice standards under CAA section 112(h); and even if the EPA could set work practice standards, CAA section 112(h) does not allow the EPA to avoid its obligation to enact standards that restrict emissions of HAPs at all times.
• the EPA has required and recognized the necessity of control for HON, P&R I, and MON PRDs in EtO service, P&R I PRDs in chloroprene service, and all Organic Liquid Distribution and P&R II PRDs, but has not applied equal controls to other PRDs or to flares above their smokeless capacity. This underscores the unlawfulness of the exemptions (at40 CFR 63.165(e)(3)(v)(B) and (C) and 40 CFR 63.670(o)(7)(ii) and (iv)), and treating these releases so differently is arbitrary and capricious.

Specifically, with regards to 40 CFR 63.670(o)(7)(ii) and (iv), several commenters said that smoking flares produce significant amounts of ‘soot’; and beyond the health risks of particulate matter, smoking flares increase production of ozone, especially in the presence of greater environmental heat. A supporter of 40 CFR 63.670(o)(7)(ii) and (iv) reiterated that the provisions are necessary because the EPA is removing the SSM provisions. The commenter also said that they supported the proposal to operate in accordance with a flare management plan during periods when the flow to the flare exceeds the smokeless capacity of the flare.

Other supporters of 40 CFR 63.165(e)(3)(v)(B) and (C) argued that there should be no limit on the number of PRD releases allowed to the atmosphere. A commenter cited MACT standards, such as LDAR programs, and contended that generally these programs do not limit the number of leaks allowed. The commenter also added that if the EPA proceeded with the proposed work practice standard, then they agreed with the EPA's decision to allow one or two releases under the conditions set forth in 40 CFR 63.165(e)(3)(v)(B) and (C). Commenters also requested that the EPA clarify that the start date for the initial three-year period for the limit on PRD releases to the atmosphere is the first full calendar year after the compliance date for the PRD work practice standard. The commenters further requested that the EPA include provisions that would not count the second event from the same equipment and same root cause within a 3-year period as a deviation where a) the root cause investigation from the first incident is not yet complete; and/or b) where the corrective action resulting from the root cause investigation requires a capital expenditure and such has been initiated and is being timely pursued.

Response: The EPA acknowledges the commenters' support for removing the SSM exemptions in the rules. As we explained in the preamble to the proposed rule (88 FR 25080, April 25, 2023), in Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008), the Court determined that the SSM exemption violates the CAA. Specifically, the court vacated the SSM exemption contained in 40 CFR 63.6(f)(1) and 40 CFR 63.6(h)(1), holding that under CAA section 302(k), emissions standards or limitations must be continuous in nature and that the SSM exemption violates the CAA's requirement that some section 112 standards apply continuously. With the issuance of the mandate in Sierra Club v. EPA, the exemption language in 63.6(f)(1) and (h)(1) is null and void and any cross reference to those provisions has no effect.

However, we disagree with other commenters suggesting that the EPA created loopholes for releases from PRDs at 40 CFR 63.165(e)(3)(v)(B) and (C) and smoking flares at 40 CFR 63.670(o)(7)(ii) and (iv) during malfunctions. At proposal, the EPA explained that “[a]lthough no statutory language compels the EPA to set standards for malfunctions, the EPA has the discretion to do so where feasible.” (88 FR 25167). We further explained that “[t]he EPA will consider whether circumstances warrant setting work practice standards for a particular type of malfunction in the SOCMI, P&R I, and P&R II source categories, and, if so, whether the EPA has sufficient information to identify the relevant best performing sources and establish a standard for such malfunctions.” (88 FR 25168.) It is very difficult to guard perfectly against acts of God and acts of terrorism. The EPA does not believe it can develop measures that would effectively limit emissions during all such acts.

Regardless, the PRD work practice standard requires redundant prevention measures, which are designed to limit the duration and quantity of releases from all atmospheric PRDs regardless of the cause. Flares are required to comply with the requirements for a continuously lit pilot flame and combustion efficiency standards ( i.e., limits on the NHVcz) at all times, including during periods of emergency flaring caused by a force majeure event. These requirements apply at all times; thus, the final work practice standards do have requirements that apply to PRDs and flares at all times and they are not contrary to the CAA requirements in CAA section 112. In addition, the work practice standard for PRDs requires installation and operation of continuous monitoring device(s) to identify when a PRD release has occurred. We also note that facilities are required to initiate a root cause analysis to assess the cause of a release, including releases determined to be caused by a force majeure event. The count of events at 40 CFR 63.165(e)(3)(v)(B) and (C) and smoking flares at 40 CFR 63.670(o)(7)(ii) and (iv) includes events for which the root cause is determined to be force majeure. In other words, there is no categorization or interpretation related to the root cause of the event; and the corrective action component of the work practice standards applies to all events regardless of the root cause and all events would count towards the violation criteria set forth in the standard. We note that further comments on the concept of “ force majeure ” and our responses to these comments can be found in section 7.2 of the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

We disagree with the comments regarding the exemptions being arbitrary and capricious. We modeled the applicability of the PRD provisions after the SCAQMD rule, based on a MACT floor analysis and considering the appropriate requirements for these types of PRDs. With regard to PRDs in EtO or chloroprene service, we stated in the preamble to the proposed rule (88 FR 25080, April 25, 2023) that any release event from a PRD in EtO (from the SOCMI source category) or chloroprene service (from the Neoprene Production source category) is a violation of the standard in order to help reduce risk from these source categories to an acceptable level.

With regard to the request that we clarify the start date for the work practice standards, the regulatory text at 40 CFR 63.165(e)(3)(iv), 40 CFR 63.165(e)(3)(v)(B) and (C) (for PRDs) and at 40 CFR 63.670(o)(7(ii) and (iv) (for smoking flares), states that the time period is based on a 3-calendar-year period. We consider 2023 to be 1 calendar year. A 3-calendar-year period in 2023 would include events that occurred in 2021, 2022, and 2023. It is a rolling average to the extent that, in 2024, one would consider events that occurred in 2022, 2023, and 2024. As indicated in 40 CFR 63.182(d)(2)(xviii)(C), each pressure release to the atmosphere, including the duration of the release, the estimated quantity of each organic HAP released, and the results of the root cause analysis and corrective action analysis completed during the reporting period must be included as part of the reporting obligation. We disagree with the comment regarding meeting certain criteria and not counting the second event from the same equipment and same root cause as a deviation. First, we want to clarify that we mean violation, not deviation. Our use of the term “deviation” in the preamble to the proposed rule was an error (however, we did use “violation” in the proposed rule text in 40 CFR 63.165). While the MON rule text uses the MON-defined term “deviation” to describe emissions events, the current (and proposed) HON rule text uses the term “violation.” There are no uses of the term “deviation” to describe an emissions event in the current HON rule text, nor any definition in the HON of that term. Therefore, given that we are building off the existing HON standards, we believe it is more appropriate to continue to use the term “violation” (in lieu of the undefined “deviation”) in all of the HON rule text. Second, at proposal, we explained that two release events with the same root cause from a single PRD in a 3-year period is a violation from the MACT standard. 88 FR 25157. The commenter requested that if a corrective action has not been implemented to resolve an issue, then related PRD releases should not be counted towards the violation; however, this result is exactly what the EPA wants to prevent by having a lower release threshold for violations when a PRD release results from the same root cause.

4. What is the rationale for our final approach and final decisions to address emissions during periods of SSM?

We evaluated all of the comments on the EPA's proposed amendments to the SSM provisions. For the reasons explained in the proposed rule (88 FR 25080, April 25, 2023), we determined that these amendments, which remove and revise provisions related to SSM, are necessary to be consistent with the requirement that the standards apply at all times. More information concerning the amendments we are finalizing for SSM is in the preamble to the proposed rule (88 FR 25080, April 25, 2023) and in the comments and our specific responses to the comments in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking. Therefore, we are finalizing our approach for the SSM provisions as proposed.

E. Amendments Addressing NSPS Subparts VV and VVa Reconsideration

1. What amendments did we propose to address the NSPS subparts VV and VVa reconsideration?

In response to the January 2008 petition for reconsideration, we proposed: (1) Definitions for “process unit” for NSPS subparts VV and VVa that are the same or essentially the same as the definition of “process unit” that was first promulgated in NSPS subpart VV (see 48 FR 48307, October 18, 1983) and that applied during the stay of the 2007 amendments to this definition in both NSPS subparts VV and VVa; (2) to remove the requirements in 40 CFR 60.482-1(g) (for NSPS subpart VV) and 40 CFR 60.482-1a(g) (for NSPS subpart VVa) that are related to a method for assigning shared storage vessels to specific process units; (3) to remove the connector monitoring provisions from NSPS subpart VVa at 40 CFR 60.482-11a in their entirety; and (4) to revise the “capital expenditure” definition in NSPS subpart VVa at 40 CFR 60.481a such that for owners or operators that start a new, reconstructed, or modified affected source prior to November 16, 2007, the variable Y ( i.e., the percent of a facility's replacement cost used in determining an adjusted annual asset guideline repair allowance) is determined from the following equation: Y = 1.0 − 0.575 log X, where the value of “X” is 1982; for owners or operators that start a new, reconstructed, or modified affected source on or after November 16, 2007, for which the NSPS subpart VVa definition of “capital expenditure” was not stayed, we proposed to continue to apply the definition in NSPS subpart VVa ( i.e., the value of “X” is 2006 minus the year of construction).

2. How did the revisions addressing the NSPS subparts VV and VVa reconsideration change since proposal?

We are finalizing the changes described in section IV.E.1 of this preamble as proposed, except for certain changes related to the “capital expenditure” definition in NSPS subpart VVa. For NSPS subpart VVa, we are finalizing the “capital expenditure” definition in NSPS subpart VVa in place during the stay of the definition for facilities that underwent a physical or operational change prior to November 16, 2007. We recognize, depending on the year a modification took place, this definition may potentially leave an indeterminant outcome ( e.g., log (X) where X is a negative value) for calculation of the adjusted annual asset guideline repair allowance. However, to the extent there were sources that encountered this scenario (where a physical or operational change between November 7, 2006 and November 16, 2007 triggered an evaluation of whether the capital expenditure was above the threshold to be considered a modification), the NSPS subpart VVa applicability determination would have been resolved a long time ago; thus, finalizing the same definition as applied during the stay would avoid upending any long-standing determinations. Therefore, in the final rule, we are finalizing the definition that was in place during the stay, which include correcting several errors made in our proposed definition and noted by commenters. Specifically, the proposed definition erroneously attached the value of “X” in the percent Y equation to the date of construction, reconstruction, and modification (as opposed to date of physical or operational change); in the final rule, we have replaced that phrasing with a reference to physical and operation change. In addition, we revised the value of “X” from “1982” to “1982 minus the year of construction.” Accordingly, in the final rule, we are revising the “capital expenditure” definition in NSPS subpart VVa at 40 CFR 60.481a such that for owners or operators that made a physical or operational change to their existing facility prior to November 16, 2007, the percent Y is determined from the following equation: Y = 1.0 − 0.575 log X, where the value of “X” is 1982 minus the year of construction; for owners or operators that made a physical or operational change to their existing facility on or after November 16, 2007, the percent Y is determined from the following equation: Y = 1.0 − 0.575 log X, where the value of “X” is 2006 minus the year of construction.

3. What key comments did we receive on the revisions addressing the NSPS subparts VV and VVa reconsideration and what are our responses?

This section provides summaries of and responses to the key comments received regarding our proposed requirements for connectors and proposed revisions to the requirements in NSPS subpart VVa for capital expenditure. Except for these comments related to the proposed requirements for connectors and capital expenditure, we did not receive many substantive comments on the other amendments related the NSPS subparts VV and VVa reconsideration. The comments we received regarding other amendments generally include issues related to the definition of “process unit.” The comments and our specific responses to these issues can be found in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

Comment: A commenter objected to the EPA removing the connector monitoring provisions from NSPS subpart VVa and only proposing them in NSPS subpart VVb. The commenter contended that the EPA did not provide sufficient justification for this change, given that the EPA's rationale was only that they agreed with Petitioners that it had not included those requirements in the November 7, 2006, proposal (72 FR 64860) but then established connector monitoring requirements in the November 16, 2007 final rule without notice and an opportunity to comment. The commenter added that the EPA must also justify why it is not appropriate to lift the stay and require connector monitoring at sources subject to NSPS subpart VVa from this point forward. The commenter listed several issues with the EPA's decision:

• The EPA must propose and provide opportunity for comment on requiring connector monitoring at sources subject to NSPS subpart VVa. The basis of the reconsideration was a lack of notice and comment, and the EPA is currently in the position to provide an opportunity for comment on those requirements yet fails to do so with no explanation.
• The EPA must justify why additional emissions reductions for sources subject to NSPS subpart VVa are no longer appropriate before simply removing the requirements in their entirety. The EPA found connector monitoring as the “best system of emission reduction” in the November 16, 2007, preamble, and the EPA has not explained why that determination was inappropriate or no longer valid. In EPA's analysis supporting the final NSPS subpart VVa, it found that the promulgated connector monitoring requirements were: (1) Common practice at many chemical manufacturing facilities, including through regulations such as HON, MON, Ethylene MACT, and the Generic MACT (40 CFR 63, subpart UU), (2) resulted in greater emission reductions (230 tpy VOC) than the changes the EPA implemented for pumps and valves (94 tpy VOC) in NSPS subpart VVa, and (3) were achieved at a cost $2,500 per ton of VOC reduced.
• The EPA must justify why the same requirements it is proposing to remove from NSPS subpart VVa are only appropriate for NSPS subpart VVb.

The commenter asserted that the EPA can and must lift the stay as it relates to connector monitoring in 40 CFR 60.482-11a and require compliance with that section from that date forward in order to ensure the critical (and cost-effective) environmental protections are implemented, while avoiding concerns of retroactive application of standards. The EPA could do this through providing language that the standards were stayed from June 2, 2008, until the date of the final rule, but are in effect moving forward.

Response: As previously discussed in the preamble to the proposed rule (88 FR 25080, April 25, 2023), we proposed to remove the connector monitoring requirements in NSPS subpart VVa that have been stayed since 2008. The EPA disagrees with the comment that, having granted reconsideration of these requirements because they were finalized without proposal and an opportunity for comment, the EPA must now propose to remove the stay and provide the public an opportunity to comment on the connector requirements. While CAA section 307(d)(7)(B) requires that the EPA grant reconsideration in this situation (where the grounds for objecting to the standard arose after the period for public comment, in this case when the final rule was promulgated), nothing in CAA section 307(d)(7)(B) or elsewhere in the CAA dictates what actions the EPA must take in a reconsideration proceeding, much less requiring that the EPA propose the connector requirements for comment; nor has the commenter cited any legal authority requiring such action from the EPA in an administrative reconsideration proceeding under CAA section 307(d)(7)(B).

In its reconsideration of the connector requirements in NSPS subpart VVa, the EPA took into account that these requirements have been stayed since June 2008, over 15 years ago and shortly after the promulgation of NSPS subpart VVa in November 2007. In light of the fact that the connector requirements have not been part of NSPS subpart VVa's long implementation history, the EPA does not think it is appropriate to amend NSPS subpart VVa now to add a new requirement for new equipment ( i.e., connectors) for sources constructed, reconstructed or modified between November 7, 2006 and April 26, 2023, which are existing sources for purposes of the newly promulgated NSPS subpart VVb. The EPA believes that standards for previously unregulated sources such as the connectors are better suited moving forward for new and modified sources under NSPS subpart VVb. For the reasons stated above, the EPA is finalizing the removal of the connector requirements in NSPS subpart VVa, as proposed.

Comment: Commenters requested the EPA correct the formula for calculating the value of “X” in the definition of “Capital Expenditure” in the proposed NSPS subpart VVa. A commenter explained that the EPA proposed a value of “1982” for “X” for owners or operators “that start a new, reconstructed, or modified affected source prior to November 16, 2007.” The commenter contended that this results in a negative value for “Y” (that is, −0.89, or 1.0-0.575log(1982)), being effectively an indeterminant outcome for calculation of the adjusted annual asset guideline repair allowance. Another commenter recommended that the EPA revise “X” from “1982” to “1982—the year of construction” for owners or operators “that start a new, reconstructed, or modified affected source prior to November 16, 2007.”

Another commenter contended that the EPA's proposed definition for capital expenditures in NSPS subpart VVa narrows the reach of modification and would result in the exclusion of certain process units from applicability to the subpart through modification. For NSPS subpart VVa, the commenter contended the EPA has made significant errors in defining how sources would determine if modification has occurred and went beyond addressing the issues raised by the petitioners requesting reconsideration of the capital expenditure definition. The commenter asserted that it is inappropriate to include a definition for modification related to a date of construction, reconstruction, or modification that operates apart from the applicability of the individual subpart. The commenter explained that a source that is constructed or reconstructed after the applicability date of the subpart (November 7, 2006, for NSPS subpart VVa) is automatically subject to the standards of that subpart and modification has no relevance unless a subpart with a later applicability date is promulgated. The commenter added that a source is not defined as modified unless it undergoes a physical or operational change that results in an increase in emissions. The commenter contended that a definition of capital expenditure that is reliant on the dates of “construction, reconstruction, or modification” is not relevant to and has no bearing on whether a source has been modified. The commenter concluded that the EPA must redefine capital expenditure without specifying construction, reconstruction, or modification dates. The commenter recommended that the EPA should seek to address the definition of capital expenditure as it applies to the subset of physical and operational changes that occurred specifically between November 7, 2006, and November 16, 2007. The commenter added that for those sources that would have utilized the capital expenditure equation in NSPS subpart VV, it is appropriate to define the value of “X” as “1982 minus the year of construction” or simply cross-reference the capital expenditure definition at 40 CFR 60.481. The commenter stated that the definition of capital expenditure as it relates to physical and operational changes that take place after November 16, 2007 (the promulgation date of NSPS subpart VVa), was not under reconsideration and should remain as promulgated such that the EPA define “X” based on the dates of “physical or operational changes” regardless of the date of construction, reconstruction, or modification, and specifically, for physical or operational changes that take place after November 16, 2007, “X” should remain defined as “2006 minus the year of construction.”

Response: We agree that errors were made in the proposed “capital expenditure” definition in NSPS subpart VVa. The proposed definition, in relevant part, stated that

“(2) The percent Y is determined from the following equation: Y = 1.0 − 0.575 log X, where X is:

(i) 2006 minus the year of construction for owners or operators that start a new, reconstructed, or modified affected source on or after November 16, 2007, or

(ii) 1982 for owners or operators that start a new, reconstructed, or modified affected source prior to November 16, 2007;”

We agree with the comment that the proposed definition erroneously relies on a sources' construction, reconstruction, or modification date for calculating capital expenditure to determine whether modification has been triggered for that source. Sources constructed, modified, or reconstructed after November 7, 2006, are affected facilities under NSPS subpart VVa ( i.e., they are subject to the standards of NSPS subpart VVa); whether any such NSPS subpart VVa affected facility has subsequently incurred capital expenditure that would constitute “modification” is irrelevant as the only purpose for that capital expenditure calculation is to determine NSPS subpart VVa applicability, which we already know it does. The commenter also correctly notes that modification is determined by whether there is a physical or operational change that results in an increase in emissions. See 40 CFR 60.2 and CAA section 111(a)(4). For the reasons stated above, in the final rule, we have revised the proposed “capital expenditure” definition by referencing the date of a physical or operational change to a source instead its construction, modification and reconstruction date.

Regarding the value of “X” for owners and operators that made a physical or operation change to their existing facility prior to November 16, 2007, commenters are correct that the value of “X” being 1982 results in a negative value for the variable “Y”; the proposed regulation edits (see Docket Item No. EPA-HQ-OAR-2022-0730-0067) mistakenly required the value of “X” be 1982 instead of the intended equation. The intended equation for “X” was 1982 minus the year of construction; this equation was described in the proposal preamble (88 FR 25172) and aligns with the commenters' recommendation, which we acknowledge could still result in a nonsensical value for the variable “Y” for certain scenarios. However, the impact of this issue is unclear, as it would affect only sources that made a physical or operational change within the relevant one-year period (after November 7, 2006 but before November 16, 2007). To the extent there were such sources, we believe that they had long ago found ways to resolve the issue and determine NSPS subpart VVa applicability, perhaps in consultation with the relevant EPA region or delegated State agencies; thus, finalizing the same definition as that which was in effect during the relevant one-year period would avoid upending any such long-standing resolutions or determinations by owners/operators and/or EPA or delegated State agencies.

For the reasons described above, we are finalizing the equation for calculating the variable “Y” in the definition of “capital expenditure” in NSPS subpart VVa as follows:

(2) The percent Y is determined from the following equation: Y = 1.0 − 0.575 log X, where X is:

(i) 2006 minus the year of construction if the physical or operational change to the existing facility was on or after November 16, 2007, or

(ii) 1982 minus the year of construction if the physical or operational change to the existing facility was prior to November 16, 2007.

4. What is the rationale for our final approach and final decisions to address the NSPS subparts VV and VVa reconsideration?

The amendments address the following issues raised in the January 2008 petition for reconsideration: (1) The clarification of the definition of process unit in NSPS subparts VV and VVa; (2) the assignment of shared storage vessels to specific process units in NSPS subparts VV and VVa; (3) the monitoring of connectors in NSPS subpart VVa; and (4) the definition of capital expenditure in NSPS subpart VVa. More information concerning the amendments we are finalizing to address these issues is in the preamble to the proposed rule and in the comments and our specific responses to the comments in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

F. Other Amendments to the NESHAP and NSPS

1. What other amendments did we propose for the SOCMI, P&R I, and P&R II source categories?

We proposed a requirement that owners or operators submit electronic copies of certain required performance test reports, flare management plans, and periodic reports (including fenceline monitoring reports for HON and the P&R I NESHAP) through the EPA's CDX using the CEDRI (at 40 CFR 63.108(e), 40 CFR 63.152(c) and (h), and 40 CFR 63.182(d) and (e) (for HON), 40 CFR 63.506(e)(6), and (i)(3) (for the P&R I NESHAP), and 40 CFR 63.528(a) and (d) (for the P&R II NESHAP), 40 CFR 60.486(l), and 60.487(a) and (g) through (i) (for NSPS subpart VV), 40 CFR 60.486a(l), and 60.487a(a) and (g) through (i) (for NSPS subpart VVa), 40 CFR 60.486b(l), and 60.487b(a) and (g) through (i) (for NSPS subpart VVb), 40 CFR 60.615(b), (j), (k), and (m) through (o) (for NSPS subpart III), 40 CFR 60.615a(b), (h) through (l), and (n), and 40 CFR 619a(e) (for NSPS subpart IIIa), 40 CFR 60.665(b), (l), (m), and (q) through (s) (for NSPS subpart NNN), 40 CFR 60.665a(b), (h), (k) through (n), and (p), and 40 CFR 669a(e) (for NSPS subpart NNNa), 40 CFR 60.705(b), (l), (m), and (u) through (w) (for NSPS subpart RRR), and 40 CFR 60.705a(b), (k) through (o), and (v), and 40 CFR 709a(e) (for NSPS subpart RRRa)). We also proposed two narrow circumstances in which owners or operators may seek extensions to the deadline if they are prevented from reporting by conditions outside of their control within five business days of the reporting deadline. We proposed that an extension may be warranted due to outages of the EPA's CDX or CEDRI that precludes an owner or operator from accessing the system and submitting required reports. We also proposed that an extension may be warranted due to a force majeure event, such as an act of nature, act of war or terrorism, or equipment failure or safety hazards beyond the control of the facility.

In addition, we proposed the restructuring of all HON definitions from NESHAP subparts G and H ( i.e., 40 CFR 63.111 and 40 CFR 63.161, respectively) into the definition section of NESHAP subpart F ( i.e., 40 CFR 63.101); and we proposed to consolidate differences between certain definitions in these subparts.

We proposed adding monitoring requirements at 40 CFR 63.114(a)(5)(v), 40 CFR 63.120(d)(1)(iii), 40 CFR 63.127(b)(4), and 40 CFR 63.139(d)(5) (for HON), and 40 CFR 63.484(t), 40 CFR 63.485(x), and 40 CFR 63.489(b)(10) (for the P&R I NESHAP) for owners or operators using adsorbers that cannot be regenerated and regenerative adsorbers that are regenerated offsite. We also proposed that owners or operators of this type of APCD use dual (two or more) adsorbent beds in series and conduct monitoring of HAP or TOC on the outlet of the first adsorber bed in series using a sample port and a portable analyzer or chromatographic analysis.

In addition, we proposed several corrections to the calibration drift assessment requirements in NSPS subpart VVa at 40 CFR 60.485a(b)(2) including: (1) Correcting a regulatory citation to read “§ 60.486a(e)(8)” instead of “§ 60.486a(e)(7)”; (2) removing the extraneous sentence “Calculate the average algebraic difference between the three meter readings and the most recent readings and the most recent calibration value.”; (3) providing clarity in the mathematical step of the assessment by replacing the sentence “Divide this algebraic difference by the initial calibration value and multiply by 100 to express the calibration drift as a percentage.” with “Divide the arithmetic difference of the initial and post-test calibration response by the corresponding calibration gas value for each scale and multiply by 100 to express the calibration drift as a percentage.”; and (4) providing clarity by making other minor textural changes to the provisions related to the procedures for when a calibration drift assessment shows negative or positive drift of more than 10 percent.

We also proposed at 40 CFR 63.103(b)(1) (for HON), 40 CFR 63.490(g) and 40 CFR 63.504(a) (for the P&R I NESHAP), and 40 CFR 64.525(a), (e), and (m) (for the P&R II NESHAP) that owners and operators would be required to conduct subsequent performance testing on non-flare control devices no later than 60 calendar months after the previous performance test.

We also proposed to: (1) Remove the provisions at 40 CFR 63.110(h) that allow compliance with certain portions of 40 CFR part 264, subpart AA or CC in lieu of portions of NESHAP subpart G; and (2) remove the provisions at 40 CFR 63.110(i) and 40 CFR 60.160(g) that allow compliance with certain portions of 40 CFR part 65 in lieu of portions of NESHAP subparts G and H.

Finally, we proposed revisions to clarify text or correct typographical errors, grammatical errors, and cross-reference errors. These editorial corrections and clarifications are discussed in section III.E.5.f of the proposal preamble (see 88 FR 25080, April 25, 2023).

2. How did the other amendments for the SOCMI, P&R I, and P&R II source categories change since proposal?

Based on comments received on the proposed rulemaking, we are making some changes to the amendments described in section IV.F.1 of this preamble.

With regard to electronic reporting, we are making several minor clarifying edits to the spreadsheet reporting templates (the final versions of the templates will be located on the CEDRI website). We are also making only minor changes to the HON definitions.

In addition, for adsorbers that cannot be regenerated and regenerative adsorbers that are regenerated offsite, we have clarified the proposed rule text in this final action that the monitoring plan provisions in 40 CFR 63.120(d)(2) and (3) do not apply to HON sources subject to the monitoring provisions in 40 CFR 63.120(d)(1)(iii); and the monitoring plan provisions in 40 CFR 63.120(d)(2) and (3) do not apply to P&R I sources subject to the monitoring provisions in 40 CFR 63.120(d)(1)(iii) (via 40 CFR 63.484(t) and 40 CFR 63.485(x)).

With regard to overlap provisions, we are: (1) Revising 40 CFR 63.160(b)(1) and (c)(1) in the final rule such that compliance with HON subpart H constitutes compliance with NSPS subpart VVa provided the owner or operator continues to comply with 40 CFR 60.480a(e)(2)(i); and (2) revising 40 CFR 63.160(b)(1) and (c)(1) in the final rule such that compliance with HON subpart H constitutes compliance with NSPS subpart VVb provided the owner or operator continues to comply with 40 CFR 60.480b(e)(2)(i). We have also revised 40 CFR 60.480b(e)(2)(i) in the final rule to require compliance with 40 CFR 60.482-7b ( i.e., the standards for gas and light liquid valves in NSPS subpart VVb) in addition to the requirements of 40 CFR 60.485b(d), (e), and (f), and 40 CFR 60.486b(i) and (j).

3. What key comments did we receive on the other amendments for the SOCMI, P&R I, and P&R II source categories and what are our responses?

We did not receive many substantive comments on the other amendments discussed in this section IV.F of this preamble. The comments we received regarding other amendments generally include issues related to electronic reporting, the restructuring of all HON definitions, adsorbers that cannot be regenerated and regenerative adsorbers that are regenerated offsite, overlap provisions, and revisions that we proposed for clarifying text or correcting typographical errors, grammatical errors, and cross-reference errors. The comments and our specific responses to these issues can be found in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

4. What is the rationale for our final approach and final decisions regarding the other amendments for the SOCMI, P&R I, and P&R II source categories?

Based on the comments received for these other amendments, we are generally finalizing all proposed requirements. In a few instances, we received comments that led to additional minor editorial corrections and technical clarifications being made in the final rule, and our rationale for these corrections and technical clarifications can be found in section IV.F.3 of this preamble and in the document titled Summary of Public Comments and Responses for New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this rulemaking.

V. Summary of Cost, Environmental, and Economic Impacts and Additional Analyses Conducted

A. What are the affected sources?

There are approximately 207 facilities subject to the HON, 19 P&R I facilities (and 10 of these P&R I facilities are collocated with HON processes), and 5 P&R II facilities (and 3 of these P&R II facilities are collocated with HON processes). We also estimate that two additional HON facilities will be newly constructed over the next 3 years. The Office of Enforcement and Compliance Assurance's ECHO (Enforcement and Compliance History Online) tool ( https://echo.epa.gov ) indicates there are currently 592 SOCMI facilities subject to subpart VV or VVa; and 284 SOCMI facilities subject to at least one of the process vent NSPS subparts III, NNN, and/or RRR. The list of facilities is available in the document titled Lists of Facilities Subject to the HON, Group I and Group II Polymers and Resins NESHAPs, and NSPS subparts VV, VVa, III, NNN, and RRR (see Docket Item No. EPA-HQ-OAR-2022-0730-0069). We estimate that there will be one new greenfield facility, six new affected facilities constructed at existing plant sites, and 12 modified/reconstructed facilities subject to NSPS subpart IIIa, NNNa, and/or RRRa in the next 5 years. We estimate there will be one new greenfield facility, 34 new affected facilities constructed at existing plant sites, and one modified facility subject to NSPS subpart VVb in the next 5 years (and no affected facilities will trigger NSPS subpart VVa reconstruction requirements).

B. What are the air quality impacts?

This final action will reduce HAP emissions by at least 1,372 tpy and VOC emissions by 3,820 tpy from HON, P&R I, and P&R II emission sources as well as the NSPS SOCMI air oxidation unit processes, distillation operations, reactor processes, and equipment leaks sources. These emission reductions are broken down by rule as follows. Considering reported emissions inventories for EtO and chloroprene, we estimate that the final amendments to the NESHAP will reduce overall HAP emissions from the SOCMI source category by approximately 1,107 tpy (and 1,919 tpy of VOC), reduce overall HAP emissions from the P&R I source categories by approximately 264 tpy (and 278 tpy of VOC), and reduce overall HAP and VOC emissions from the P&R II source categories by approximately 1 tpy. We note that these emissions reductions do not consider the potential excess emissions reductions from flares that could result from the final monitoring requirements; we estimate flare excess emissions reductions of 4,858 tpy HAP and 19,889 tpy VOC. Based on our analysis of the finalized actions described in sections III.B.2, III.D.2, and III.E of this preamble for the NSPS, we estimate that the final amendments to the NSPS would reduce VOC emissions from the SOCMI source category by approximately 1,622 tpy. The Agency was unable to estimate HAP emission reductions for the final amendments to the NSPS in this rulemaking. Emission reductions and secondary impacts ( e.g., emission increases associated with supplemental fuel or additional electricity) by rule are listed below. The only change in air impacts since proposal stems from our reevaluation related to the TRE removal for HON and the P&R I NESHAP, and its discontinued use in the new NSPS subparts IIIa, NNNa, and RRRa (based on comments received as discussed in sections IV.B.3.a.i and IV.B.3.b.i of this preamble).

1. HON

For the HON, the EPA estimates HAP and VOC emission reductions of approximately 1,107 and 1,919 tpy, respectively. The EPA estimates these reductions include an approximate 54 tpy reduction in EtO emissions (from reported emissions inventories) and a reduction of 20,177 tpy of methane emissions. The EPA also estimates that the final action would result in additional emissions of 714 tpy of CO; 609,761 tpy of CO₂; 277 tpy of NO_X (including 5.3 tpy of N₂ O); 12.7 tpy of particulate matter; and 1.0 tpy of SO₂. More information about the estimated emission reductions and secondary impacts of this final action for the HON can be found in the RIA accompanying this rulemaking, the documents referenced in sections III.B through III.D of the preamble to the proposed rule (88 FR 25080, April 25, 2023), and in the document titled Clean Air Act Section 112(d)(6) Technology Review for Continuous Process Vents Located in the SOCMI Source Category that are Associated with Processes Subject to HON, Continuous Front-end and Batch Front-end Process Vents Associated with Processes Subject to Group I Polymers and Resins NESHAP, and Process Vents Associated with Processes Subject to Group II Polymers and Resins NESHAP—FINAL, which is available in the docket for this rulemaking.

2. P&R I NESHAP

For the P&R I NESHAP, the EPA estimates HAP and VOC emission reductions of approximately 264 and 278 tpy, respectively. The EPA estimates these reductions include an approximate 14 tpy reduction in chloroprene emissions (from reported emissions inventories); and a reduction of 2,018 tpy of methane emissions. The EPA also estimates that the final action would result in additional emissions of 110 tpy of CO; 115,975 tpy of CO₂; 75 tpy of NO_X (including 1.5 tpy of N₂ O); 4.8 tpy of particulate matter; and 0.4 tpy of SO₂. More information about the estimated emission reductions and secondary impacts of this final action for the P&R I NESHAP can be found in the RIA accompanying this rulemaking, the documents referenced in sections III.B through III.D of the preamble to the proposed rule (88 FR 25080, April 25, 2023), and in the document titled Clean Air Act Section 112(d)(6) Technology Review for Continuous Process Vents Located in the SOCMI Source Category that are Associated with Processes Subject to HON, Continuous Front-end and Batch Front-end Process Vents Associated with Processes Subject to Group I Polymers and Resins NESHAP, and Process Vents Associated with Processes Subject to Group II Polymers and Resins NESHAP—FINAL, which is available in the docket for this rulemaking.

3. P&R II NESHAP

For the P&R II NESHAP, the EPA estimates 1 tpy of HAP and VOC emission reductions. The EPA also estimates that the final action would not have any secondary pollutant impacts. More information about the estimated emission reductions and secondary impacts of this final action for the P&R II NESHAP can be found in the RIA accompanying this rulemaking and the documents referenced in sections III.B through III.D of the preamble to the proposed rule (88 FR 25080, April 25, 2023).

4. NSPS Subpart VVb

For the final NSPS subpart VVb, the EPA estimates VOC emission reductions of approximately 340 tpy. The EPA estimates that the final action would not have any secondary pollutant impacts. More information about the estimated emission reductions and secondary impacts of this final action for NSPS subpart VVb can be found in the RIA accompanying this rulemaking and, in the document titled CAA 111(b)(1)(B) review for the SOCMI Equipment Leaks NSPS Subpart VVa (see Docket Item No. EPA-HQ-OAR-2022-0730-0096).

5. NSPS Subparts IIIa, NNNa, and RRRa

For the final NSPS subparts IIIa, NNNa, and RRRa, the EPA estimates VOC emission reductions of approximately 1,281 tpy and a reduction of 757 tpy of methane emissions. The EPA estimates that the final action result in additional emissions of 21.5 tpy of CO; 15,370 tpy of CO₂; and 4.0 tpy of NO_X (including 0.1 tpy of N₂ O). More information about the estimated emission reductions and secondary impacts of this final action for NSPS subparts IIIa, NNNa, and RRRa can be found in the RIA accompanying this rulemaking and in the document titled CAA 111(b)(1)(B) review for the SOCMI air oxidation unit processes, distillation operations, and reactor processes NSPS subparts III, NNN, and RRR—FINAL, which is available in the docket for this rulemaking.

C. What are the cost impacts?

This final action will cumulatively cost (in 2021 dollars) approximately $522 million in total capital costs and $194 million per year in total annualized costs (including product recovery), based on our analysis of the final action described in sections III and IV of this preamble (see table 6 in section V.C.1 of this preamble). Costs by rule are listed below. The only change in cost impacts since proposal stems from our reevaluation related to the TRE removal for HON and the P&R I NESHAP, and its discontinued use in the new NSPS subparts IIIa, NNNa, and RRRa (based on comments received as discussed in sections IV.B.3.a.i and IV.B.3.b.i of this preamble).

1. HON

For the HON, the EPA estimates this final action will cost approximately $455 million in total capital costs and $169 million per year in total annualized costs (including product recovery). More information about the estimated cost of this final action for the HON can be found in the documents referenced in sections III.B through III.D of the preamble to the proposed rule (88 FR 25080, April 25, 2023), and in the document titled Clean Air Act Section 112(d)(6) Technology Review for Continuous Process Vents Located in the SOCMI Source Category that are Associated with Processes Subject to HON, Continuous Front-end and Batch Front-end Process Vents Associated with Processes Subject to Group I Polymers and Resins NESHAP, and Process Vents Associated with Processes Subject to Group II Polymers and Resins NESHAP—FINAL, which is available in the docket for this rulemaking. The HON represents the majority of total estimated costs for this action (see Table 6 of this preamble).

2. P&R I NESHAP

For the P&R I NESHAP, the EPA estimates this final action will cost approximately $28 million in total capital costs and $15 million per year in total annualized costs (including product recovery). More information about the estimated cost of this final action for the P&R I NESHAP can be found in the documents referenced in sections III.B through III.D of the preamble to the proposed rule (88 FR 25080, April 25, 2023), and in the document titled Clean Air Act Section 112(d)(6) Technology Review for Continuous Process Vents Located in the SOCMI Source Category that are Associated with Processes Subject to HON, Continuous Front-end and Batch Front-end Process Vents Associated with Processes Subject to Group I Polymers and Resins NESHAP, and Process Vents Associated with Processes Subject to Group II Polymers and Resins NESHAP—FINAL, which is available in the docket for this rulemaking.

3. P&R II NESHAP

For the P&R II NESHAP, the EPA estimates this final action will cost approximately $2.9 million in total capital costs and $1.7 million per year in total annualized costs (including product recovery). More information about the estimated cost of this final action for the P&R II NESHAP can be found in the documents referenced in sections III.B through III.D of the preamble to the proposed rule (88 FR 25080, April 25, 2023).

4. NSPS Subpart VVb

For the final NSPS subpart VVb, the EPA estimates this final action will cost approximately $7.7 million in total capital costs and $1.1 million per year in total annualized costs (including product recovery). More information about the estimated cost of this final action for NSPS subpart VVb can be found in the document titled CAA 111(b)(1)(B) review for the SOCMI Equipment Leaks NSPS Subpart VVa (see Docket Item No. EPA-HQ-OAR-2022-0730-0096).

5. NSPS Subparts IIIa, NNNa, and RRRa

For the final NSPS subparts IIIa, NNNa, and RRRa, the EPA estimates this final action will cost approximately $27.8 million in total capital costs and $6.3 million per year in total annualized costs (including product recovery). More information about the estimated cost of this final action for NSPS subparts IIIa, NNNa, and RRRa can be found in the document titled CAA 111(b)(1)(B) review for the SOCMI air oxidation unit processes, distillation operations, and reactor processes NSPS subparts III, NNN, and RRR—FINAL, which is available in the docket for this rulemaking.

D. What are the economic impacts?

The EPA conducted economic impact analyses for this rulemaking, in a document titled Regulatory Impact Analysis for the Final New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry, which is available in the docket for this action. The economic impact analyses contain two parts. The economic impacts of the final rulemaking on small entities are calculated as the percentage of total annualized costs incurred by affected ultimate parent owners to their revenues. This ratio provides a measure of the direct economic impact to ultimate parent owners of HON, P&R I, and P&R II facilities and NSPS subpart VVb, IIIa, NNNa, and RRRa facilities while presuming no impact on consumers. We estimate the average small entity impacted by this final action will incur total annualized costs of 0.5 percent of their revenue, with none exceeding 1.3 percent, not considering product recovery from compliance. With product recovery, the EPA estimates that the average small entity impacted by the rulemaking will incur total annualized costs of 0.49 percent of their revenue, with none exceeding 1.4 percent. We estimate that 25 percent (2 in total) of impacted small entities will incur total annualized costs greater than 1 percent of their revenue, and none will incur total annualized costs greater than 3 percent of their revenue. These estimates are unchanged when including product recovery. This is based on a conservative estimate of costs imposed on ultimate parent companies, where total annualized costs are imposed on a facility are at the upper bound of what is possible under the rule and do not include product recovery as an offset to the annualized costs.

In addition, we provide a fuller economic impact analysis using costs of the HON and P&R I and II NESHAP that estimates changes in affected chemical product price and output related to the impact of the compliance costs on producers and consumers of such chemical products for each of these final rules. There are seven chemical products included in the economic impact analysis—butadiene, styrene, acetone, acrylonitrile, ethylene dichloride, ethylene glycol, and EtO. For the HON, chemical product prices are estimated to increase from less than 0.01 percent to 0.61 percent, and output by product is estimated to decrease by less than 0.01 percent to 0.54 percent. For the two P&R NESHAP, chemical product prices are estimated to increase by less than 0.01 percent to 0.05 percent, and output by product is estimated to decrease by less than 0.01 percent to 0.09 percent. More explanation of these economic impacts can be found in the Regulatory Flexibility Act (RFA) section later in this preamble and in the economic impact analysis that is included in the RIA for this final rulemaking.

E. What are the benefits?

The emissions controls required by these rules are expected to reduce emissions of a number of HAP. As stated in section V.B of this preamble, this final action will reduce HAP emissions by at least 1,372 tpy and VOC emissions by 3,820 tpy from HON, P&R I, and P&R II emission sources as well as the NSPS SOCMI air oxidation unit processes, distillation operations, reactor processes, and equipment leaks sources (see Table 7 of this preamble). The health effects associated with the main HAP of concern from SOCMI (found within the HON), P&R I, and P&R II source categories are discussed fully in Chapter 4 of the RIA: EtO (Section 4.1.1), chloroprene (Section 4.1.2), benzene (Section 4.1.3), 1,3-butadiene (Section 4.1.4), vinyl chloride (Section 4.1.5), ethylene dichloride (Section 4.1.6), chlorine (Section 4.1.7), maleic anhydride (Section 4.1.8) and acrolein (Section 4.1.9). This final action is projected to reduce EtO emissions from HON processes by approximately 54 tpy and reduce chloroprene emissions from Neoprene Production processes subject to the P&R I NESHAP by approximately 14 tpy. We also estimate that the final amendments to the NESHAP will reduce other HAP emissions (excluding EtO and chloroprene) from the SOCMI, P&R I, and P&R II source categories by approximately 1,304 tpy. We also estimate that the final amendments to the NESHAP will reduce excess emissions of HAP from flares in the SOCMI and P&R I source categories by an additional 4,858 tpy. The Agency was unable to estimate HAP emission reductions for the final amendments to the NSPS in this rulemaking.

Quantifying and monetizing the economic value of reducing the risk of cancer and non-cancer effects is made difficult by the lack of a central estimate of cancer and non-cancer risk and estimates of the value of an avoided case of cancer (fatal and non-fatal) and morbidity effects. Due to methodology and data limitations, we did not attempt to monetize the health benefits of reductions in HAP in this analysis. Instead, we are providing a qualitative discussion in the RIA of the health effects associated with HAP emitted from sources subject to control under the final action. Health effects from reduced exposure to EtO, chloroprene, benzene, 1,3-butadiene, vinyl chloride, ethylene dichloride, chlorine, maleicanhydride, and acrolein are all HAP emissions expected to be reduced by this rule. These pollutants all have been associated with cancer risk is human among other acute health effects.

The emission controls installed to comply with these final rules are also expected to reduce VOC emissions which, in conjunction with NO_X and in the presence of sunlight, form ground-level ozone (O₃). This section reports the estimated ozone-related benefits of reducing VOC emissions in terms of the number and value of avoided ozone-attributable deaths and illnesses.

As a first step in quantifying O₃ -related human health impacts, the EPA consults the Integrated Science Assessment for Ozone (Ozone ISA) as summarized in the Technical Support Document for the Final Revised Cross State Air Pollution Rule Update. This document synthesizes the toxicological, clinical, and epidemiological evidence to determine whether each pollutant is causally related to an array of adverse human health outcomes associated with either acute ( i.e., hours or days-long) or chronic ( i.e., years-long) exposure. For each outcome, the Ozone ISA reports this relationship to be causal, likely to be causal, suggestive of a causal relationship, inadequate to infer a causal relationship, or not likely to be a causal relationship.

In brief, the Ozone ISA found short-term (less than one month) exposures to ozone to be causally related to respiratory effects, a “likely to be causal” relationship with metabolic effects and a “suggestive of, but not sufficient to infer, a causal relationship” for central nervous system effects, cardiovascular effects, and total mortality. The Ozone ISA reported that long-term exposures (one month or longer) to ozone are “likely to be causal” for respiratory effects including respiratory mortality, and a “suggestive of, but not sufficient to infer, a causal relationship” for cardiovascular effects, reproductive effects, central nervous system effects, metabolic effects, and total mortality.

The combined total present value (PV) of the monetized human health benefits for this final action are $77 million and $690 million at a 3 percent discount rate and $53 million and $475 million at a 7 percent discount rate. The combined total PV of the net monetized benefits (monetized health benefits plus monetized climate benefits minus climate disbenefits) for the final amendments are negative $89 million at the 3 percent discount rate to negative $110 million at the 7 percent discount rate and $480 million at the 3 percent discount rate to $270 million at the 7 percent discount rate. The combined total equivalent annual value (EAV) of the benefits for the final amendments are negative $7 million at the 3 percent discount rate to negative $7.7 million at the 7 percent discount rate and $40 million at the 3 percent discount rate to negative $34 million at the 7 percent discount rate. See Table 18 in section VI.A of this preamble for additional details. For all estimates, we summarized the monetized ozone-related health benefits using discount rates of 3 percent and 7 percent for the 15-year analysis period of these rules discounted back to 2023 rounded to 2 significant figures. We present two benefits estimates that are separated by the word “and” to signify that they are two separate estimates. The estimates do not represent lower- and upper-bound estimates. For a full explanation of why we present monetized benefits estimates in this way, please refer to Chapter 4 of the RIA. For the full set of underlying calculations see the benefits workbook in the RIA, which is available in the docket for this rulemaking. In addition, we include the monetized disbenefits ( i.e., negative effects) from additional CO₂ and NO_X emissions, which occur with the HON, the P&R I NESHAP, and NSPS IIIa, NNNa, and RRRa, but not the P&R II NESHAP or NSPS subpart VVb since there are no additional CO₂ emissions as a result of these two final rules.

1. HON

The PV of the monetized human health benefits for the HON are $70 million and $630 million at a 3 percent discount rate and $48 million and $420 million at a 7 percent discount rate. The PV of the net monetized benefits (monetized health benefits plus monetized climate benefits minus climate disbenefits) for the final amendments for the HON are negative $70 million at the 3 percent discount rate to negative $92 million at the 7 percent discount rate and $490 million at the 3 percent discount rate to $280 million at the 7 percent discount rate. The EAV of the benefits for the final amendments for the HON are negative $5.1 million at the 3 percent discount rate to negative $5.8 million at the 7 percent discount rate and $42 million at the 3 percent discount rate to negative $35 million at the 7 percent discount rate. In addition, this rule will provide unmonetized benefits from the reduction of 1,107 tons of HAP emission reductions. This includes positive health effects from reduced exposure to EtO, chloroprene, benzene, 1,3-butadiene, vinyl chloride, ethylene dichloride, chlorine, maleicanhydride, and acrolein.

2. P&R I NESHAP

The PV of the monetized human health benefits for the P&R I NESHAP are negative $0.2 million and negative $1.7 million at a 3 percent discount rate and negative $0.2 million and negative $1.5 million at a 7 percent discount rate. The PV of the net monetized benefits (monetized health benefits plus monetized climate benefits minus monetized climate disbenefits) for the final amendments for the P&R I NESHAP are negative $22 million at the 3 percent discount rate to negative $22 million at the 7 percent discount rate and negative $24 million at the 3 percent discount rate to negative $24 million at the 7 percent discount rate. The EAV of the benefits for the final amendments for the P&R I NESHAP are negative $1.7 million at the 3 percent discount rate to negative $1.7 million at the 7 percent discount rate and negative $1.8 million at the 3 percent discount rate to negative $1.8 million at the 7 percent discount rate. In addition, this rule will provide unmonetized benefits from 264 tpy of HAP reductions, including an approximate 14 tpy reduction in chloroprene emissions.

3. P&R II NESHAP

The PV of the net monetized benefits (monetized health benefits plus monetized climate benefits minus monetized climate disbenefits) for the final amendments for the P&R II NESHAP are zero since there are minimal VOC emission reductions (no more than 1 tpy), and there are no changes in climate-related emissions (CO₂, methane, N₂ O).

4. NSPS Subpart VVb

For the final NSPS subpart VVb, the EPA the EPA elected to use the benefit per-ton (BPT) approach because we cannot be confident of the location of new facilities that would be subject to these final NSPS, the EPA elected to use the BPT approach. BPT estimates provide the total monetized human health benefits (the sum of premature mortality and premature morbidity) of reducing one ton of the VOC precursor for ozone from a specified source. Specifically, in this analysis, we multiplied the estimates from the SOCMI sector by the corresponding emission reductions. Also, there are no climate benefits or disbenefits associated with this final NSPS. Thus, all monetized benefits are human health benefits from VOC reductions. The PV of the monetized human health benefits from this subpart is $1.3 million and $12 million at a 3 percent discount rate and $0.9 million and $7.9 million at a 7 percent discount rate. The EAV of the benefits for the final NSPS subpart VVb are $0.10 million at the 3 percent discount rate to $0.09 million at the 7 percent discount rate and $0.93 million at the 3 percent discount rate to $0.82 million at the 7 percent discount rate.

5. NSPS Subpart IIIa, NNNa, and RRRa

For the final NSPS subparts IIIa, NNNa, and RRRa, the EPA elected to use the BPT approach because we cannot be confident of the location of new facilities that would be subject to these final NSPS. BPT estimates provide the total monetized human health benefits (the sum of premature mortality and premature morbidity) of reducing one ton of the VOC precursor for ozone from a specified source. Specifically, in this analysis, we multiplied the estimates from the SOCMI sector by the corresponding emission reductions. The PV of the monetized human health benefits from these three subparts are $6 million and $54 million at a 3 percent discount rate and $5.3 million and $47 million at a 7 percent discount rate.

We then add these monetized human health benefits to the monetized climate benefits and disbenefits to provide a total estimate of monetized benefits for these final NSPS. The PV of the net monetized benefits (monetized health benefits plus monetized climate benefits minus monetized climate disbenefits) for the final NSPS subparts IIIa, NNNa, and RRRa are negative $8 million and negative 56 million at the 3 percent discount rate and negative $4 million and negative $46 million at the 7 percent discount rate. The EAV of the benefits for the final NSPS subparts IIIa, NNNa, and RRRa are negative $0.6 million at the 3 percent discount rate and negative $0.3 million at the 7 percent discount rate and negative $4.7 million at the 3 percent discount rate and negative $4.9 million at the 7 percent discount rate.

F. What analysis of environmental justice did we conduct?

For purposes of analyzing regulatory impacts, the EPA relies upon its June 2016 “Technical Guidance for Assessing Environmental Justice in Regulatory Analysis,” which provides recommendations that encourage analysts to conduct the highest quality analysis feasible, recognizing that data limitations, time, resource constraints, and analytical challenges will vary by media and circumstance. The Technical Guidance states that a regulatory action may involve potential EJ concerns if it could: (1) create new disproportionate impacts on communities with EJ concerns; (2) exacerbate existing disproportionate impacts on communities with EJ concerns; or (3) present opportunities to address existing disproportionate impacts on communities with EJ concerns through this action under development.

The EPA's EJ technical guidance states that “[t]he analysis of potential EJ concerns for regulatory actions should address three questions: (A) Are there potential EJ concerns associated with environmental stressors affected by the regulatory action for population groups of concern in the baseline? (B) Are there potential EJ concerns associated with environmental stressors affected by the regulatory action for population groups of concern for the regulatory option(s) under consideration? (C) For the regulatory option(s) under consideration, are potential EJ concerns created or mitigated compared to the baseline?”

The environmental justice analysis is presented for the purpose of providing the public with as full as possible an understanding of the potential impacts of this final action. The EPA notes that analysis of such impacts is distinct from the determinations finalized in this action under CAA sections 111 and 112, which are based solely on the statutory factors the EPA is required to consider under those sections.

1. SOCMI Source Category Demographics

For the SOCMI source category, the EPA examined the potential for the 195 HON facilities (for which the EPA had HAP emissions inventories) to pose concerns to communities living in proximity to facilities, both in the baseline and under the control option established in this final action. Specifically, the EPA analyzed how demographics and risk are distributed both pre- and post-control. The methodology and detailed results of the demographic analysis are presented in the document titled Analysis of Demographic Factors for Populations Living Near Hazardous Organic NESHAP (HON) Operations—Final, which is available in the docket for this rulemaking.

To examine the potential for environmental justice concerns, the EPA conducted three different demographic analyses: a baseline proximity analysis, baseline cancer risk-based analysis ( i.e., before implementation of any controls required by this final action), and post-control cancer risk-based analysis ( i.e., after implementation of the controls required by this final action). The baseline proximity demographic analysis is an assessment of individual demographic groups in the total population living within 10 km (~6.2 miles) and 50 km (~31 miles) of the facilities. The baseline risk-based demographic analysis is an assessment of risks to individual demographic groups in the population living within 10 km and 50 km of the facilities prior to the implementation of any controls required by this final action (“baseline”). The post-control risk-based demographic analysis is an assessment of risks to individual demographic groups in the population living within 10 km and 50 km of the facilities after implementation of the controls required by this final action (“post-control”). In this preamble, we focus on the results from the demographic analyses using a 10 km radius because this buffer distance encompasses all the facility maximum individual risk (MIR) locations, captures 97 percent of the population with baseline cancer risks greater than or equal to 50-in-1 million from SOCMI source category emissions, and captures 100 percent of the population with such baseline risks greater than 100-in-1 million. The results of the demographic analyses for populations living within 50 km of facilities are included in the document titled Analysis of Demographic Factors for Populations Living Near Hazardous Organic NESHAP (HON) Operations—Final, which is available in the docket for this rulemaking.

For all three demographic analyses, the affected populations ( i.e., those living within 10 km of the facilities) are compared to the national population. The total population, population percentages, and population count for each demographic group for the entire U.S. population are shown in the column titled “Nationwide Average for Reference” in Tables 8 through 10 of this preamble. These national data are provided as a frame of reference to compare the results of the baseline proximity analysis, the baseline cancer risk-based analysis, and the post-control cancer risk-based analysis.

The results of the baseline proximity analysis indicate that a total of 9.3 million people live within 10 km of the 195 HON facilities. The percent of the population that is Black (25 percent) is more than double the national average (12 percent), and the percent of the population that is Hispanic or Latino (22 percent) is also higher than the national average (19 percent). The percent of people living below the poverty level and the percent of people over the age of 25 without a high school diploma are higher than the national averages. The results of the baseline proximity analysis indicate that the proportion of other demographic groups living within 10 km of HON facilities is similar to or below the national average.

The baseline cancer risk-based demographic analysis, which focuses on populations that have higher cancer risks, suggests that Hispanic/Latino individuals and Black individuals living near the facilities are overrepresented with respect to the national average at all cancer risk levels greater than 1-in-1 million. In addition, the percent of households with linguistic isolation (in which all household members over the age of 14 only have limited English proficiency) increases as the Hispanic/Latino population increases. At all risk levels greater than or equal to 1-in-1-million, in cases where the percentage of the population below the poverty level is 1.5 to 2 times the national average, these populations are also above the national averages for Black, American Indian or Alaska Native, Hispanic/Latino, or Other Race/Multiracial populations.

The post-control risk-based demographic analysis shows that the controls required by this final action will notably reduce the number of people who are exposed to cancer risks resulting from SOCMI source category emissions at all risk levels. At greater than or equal to a cancer risk of 1-in-1 million, the number of individuals exposed will decrease from 2.8 million to 2.7 million. At greater than or equal to a cancer risk of 50-in-1 million, the number of individuals exposed will decrease from 300,000 to 30,000. And after the control is implemented, there will be no people who are exposed to cancer risks greater than 100-in-1 million resulting from SOCMI source category emissions. Although all demographic populations will see reductions in the number of individuals exposed at each level of risk, there will be individuals who still remain at a cancer risk greater than or equal to 1-in-1 million or greater than or equal to 50-in-1 million risk post-control. The demographic composition of those individuals still exposed to risk greater than or equal to 1-in-1 million will be similar to the demographic composition of the individuals exposed at baseline. At the greater than or equal to 50-in-1 million risk level, the percentages of most demographic populations will be similar to the national average percentages with the exception of the Hispanic/Latino population, which will still be overrepresented with respect to the national average. At the greater than 100-in-1 million risk level, there will be no individuals exposed to cancer risk post-control, so there will be no disparities among demographic groups at this risk level. The actions of this final rulemaking will improve human health of current and future populations that live near these facilities. For more details see the remainder of this section.

a. Baseline Proximity Analysis

The column titled “Baseline Proximity Analysis for Pop. Living within 10 km of HON Facilities” in Tables 8 through 10 of this preamble shows the share and count of people for each of the demographic categories for the total population living within 10 km (~6.2 miles) of HON facilities. These are the results of the baseline proximity analysis and are repeated in Tables 8 through 10 of this preamble for easy comparison to the risk-based analyses discussed later.

Approximately 9.3 million people live within 10 km of the 195 HON facilities assessed. The results of the proximity demographic analysis indicate that the percent of the population that is Black (25 percent, 2.35M people) is more than double the national average (12 percent). The percent of the population that is Hispanic or Latino (22 percent, 2M people) is higher than the national average (19 percent). The percent of people living below the poverty level (19 percent, 1.75M people) and percent of people over the age of 25 without a high school diploma (16 percent, 1.5M people) are higher than the national averages (13 percent and 12 percent, respectively). The baseline proximity analysis indicates that the proportion of other demographic groups living within 10 km of HON facilities is similar to or below the national average.

b. Baseline Risk-Based Demographics

The baseline risk-based demographic analysis results are shown in the “baseline” column of Tables 8 through 10 of this preamble. This analysis focused on the populations living within 10 km (~6.2 miles) of the HON facilities with estimated cancer risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions (Table 8 of this preamble), greater than or equal to 50-in-1 million (Table 9 of this preamble), and greater than 100-in-1 million (Table 10 of this preamble). The risk analysis indicated that emissions from the source category, prior to the controls required in this final action, expose 2.8 million people living near 111 facilities to a cancer risk greater than or equal to 1-in-1 million, 322,000 people living near 21 facilities to a cancer risk greater than or equal to 50-in-1 million, and 83,000 people living near 8 facilities to a cancer risk greater than 100-in-1 million.

In the baseline, there are 2.8 million people living around 111 HON facilities with a cancer risk greater than or equal to 1-in-1 million resulting from SOCMI source category emissions. The 111 HON facilities are located across 17 states, but two-thirds of them are located in Texas and Louisiana (50 in Texas and 33 in Louisiana). Ninety percent of the people with risks greater than or equal to 1-in-1 million are living around 29 of the 111 HON facilities. All but three of these 29 facilities are located in Texas and Louisiana. The percent of the baseline population with estimated cancer risks greater than or equal to 1-in-1 million who are Black (25 percent, 692,000 people) is well above the average percentage of the national population that is Black (12 percent). The Black population living within 10 km of two facilities in Louisiana account for about a quarter of the total Black population with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions.

The percent of the population with cancer risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions prior to the controls required in this final action that is Hispanic or Latino (34 percent, 958,000 people) is significantly higher than that in the baseline proximity analysis (22 percent, 2 million people) and well above the national average (19 percent). The population around an Illinois facility is over 75 percent Hispanic or Latino, and accounts for a quarter of the Hispanic/Latino population with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions. Another group of 5 facilities in the Houston/Channelview Texas area have local populations that are between 60 and 90 percent Hispanic/Latino, and those communities account for 31 percent of the Hispanic/Latino population with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions. The percent of the population that is linguistically isolated in the baseline with cancer risks greater than or equal to 1-in-1 million (8 percent, 228,000 people) is higher than the percentage in the baseline proximity analysis (5 percent, 510,000 people). The areas with the highest Hispanic/Latino population are some of those with the highest percent linguistic isolation.

Overall, the percent of the baseline population that is American Indian or Alaska Native with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions (0.2 percent) is well below the national average (0.7 percent). The population with baseline risks resulting from SOCMI source category emissions greater than or equal to 1-in-1 million have a percent American Indian or Alaska Native population that is more than 2 times the national average. These facilities are located in Texas (3), Louisiana, Montana, Illinois, and Kansas.

The percent of the population below the poverty level with cancer risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions (18 percent, 513,000 people) is above the national average (13 percent). The percent of the population living below the poverty level within 10 km of 19 facilities is twice the national average. The percent of the population over 25 years old without a high school diploma with cancer risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions (20 percent, 561,000 people) is greater than the national average (13 percent) as well as greater than the overall percent of the population living near HON facilities who are over 25 years old without a high school diploma (16 percent, 1.5 million people).

In the baseline, there are 322,000 people living around 21 HON facilities with a cancer risk greater than or equal to 50-in-1 million resulting from SOCMI source category emissions. The 21 HON facilities are located across 6 states, but two-thirds of them are located in Texas and Louisiana. Ninety-six percent of the people with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions live around 5 HON facilities, which are located in Texas or Louisiana. The percent of the population that is Black with baseline cancer risk greater than or equal to 50-in-1 million resulting from SOCMI source category emissions (18 percent, 59,000 people) is above the national average (12 percent) but is significantly lower than the percent of the population that is Black with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions (25 percent, 692,000 people). The percentage of Black individuals is greater than the national average near over half of the facilities (12 facilities) where cancer risk is greater than 50-in-1 million resulting from HON source category emissions. The populations near two facilities in Texas account for about 70 percent of the number of Black individuals with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions.

The percentage of the population that is Hispanic/Latino with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions (25 percent, 81,000 people) is similar to the percentage of the population that is Hispanic/Latino in the total population living within 10 km of the facilities (22 percent). The percent of population that is Hispanic/Latino with cancer risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions is above the national average at over half of the facilities (13 facilities). The population near three facilities in Texas accounts for about 80 percent of the number of Latino/Hispanic people with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions.

Overall, the percent of the population that is American Indian or Alaska Native with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions (0.2 percent) is below the national average (0.7 percent). Populations near four facilities with baseline risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions have a percent American Indian or Alaska Native population that is more than 2 times the national average. These facilities are located in Texas (3) and Louisiana.

The percentage of the population with cancer risks resulting from SOCMI source category emissions greater than or equal to 50-in-1 million that are below the poverty level (15 percent), over 25 years old without a high school diploma (15 percent), or are linguistically isolated (5 percent) are similar to or slightly above the respective national averages. Of the population with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions, the percentage of the population below the poverty level is twice the national average near five facilities. For all 5 of these facilities, the percentage of the population is also 2 times the national average percentage for at least one race/ethnic demographic category.

In the baseline, there are 83,000 people living around 8 HON facilities with a cancer risk resulting from SOCMI source category emissions greater than 100-in-1 million. These 8 HON facilities are located in Texas and Louisiana. The percent of the population that is Black with baseline cancer risk greater than 100-in-1 million resulting from SOCMI source category emissions (14 percent) is just above the national average (12 percent). The percentage of the Black population with cancer risks greater than 100-in-1 million resulting from SOCMI source category emissions is between 2 to 4 times greater than the national average at three facilities in Texas and one in Louisiana.

The percentage of the population that is Hispanic/Latino with risks greater than 100-in-1 million resulting from SOCMI source category emissions (26 percent, 22,000 people) is above the national average (19 percent) and is similar to the share of the population that is Hispanic/Latino with cancer risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions (25 percent, 81,000 people). The share of the Hispanic and Latino population with cancer risks greater than 100-in-1 million resulting from SOCMI source category emissions is between 2 to 3 times greater than the national average at five facilities in Texas and one in Louisiana.

Overall, the percent of the baseline population that is American Indian or Alaska Native with risks greater than or equal to 100-in-1 million resulting from SOCMI source category emissions (0.2 percent) is well below the National Average (0.7 percent).

The percentage of the population with cancer risks greater than 100-in-1 million resulting from SOCMI source category emissions that are below the poverty level (14 percent), over 25 without a high school diploma (14 percent), or linguistically isolated (5 percent) are similar or slightly above the respective national averages. The percent of the population below the poverty level is 1.5 times the national average at five facilities. The population living around three of these facilities is also 1.5 times the national average for at least one race/ethnic demographic category.

In summary, the baseline risk-based demographic analysis, which focuses on populations that are expected to have higher cancer risks resulting from SOCMI source category emissions, suggests that Hispanic or Latino individuals are disproportionally overrepresented at all cancer risk levels. Specifically, the percentage of the population that is Hispanic/Latino is almost twice the national average at a cancer risk equal to or greater than 1-in-1 million and almost 1.5 times the national average at the 50-in-1-million and 100-in-1-million risk levels. Similarly, the Black population is disproportionately overrepresented at all cancer risk levels in the baseline risk analysis. The percentage of Black individuals with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions is twice the national average and 1.5 times the national average at the 50-in-1-million risk level. In most cases, when the percentage of the population below the poverty level is greater than 1.5 times the national average, the percentage of the population that is Black, American Indian or Alaska Native, Hispanic/Latino, or Other/Multiracial is above the national average.

c. Post-Control Risk-Based Demographics

This analysis focused on the populations living within 10 km (~6.2 miles) of the facilities with estimated cancer risks greater than or equal to 1-in-1 million (Table 8 of this preamble), greater than or equal to 50-in-1 million (Table 9 of this preamble), and greater than 100-in-1 million (Table 10 of this preamble) resulting from SOCMI source category emissions after implementation of the control options for HON sources investigated under the residual risk analysis as described in section III.B.2.a of this preamble (“post-control”). The results of the post-control risk-based demographics analysis are in the columns titled “Post-Control” of Tables 8 through 10 of this preamble. In this analysis, we evaluated how all of the controls required by this final action and emission reductions for HON processes described in this action affect the distribution of risks. This makes it possible to characterize the post-control risks and to evaluate whether the final action creates or mitigates potential environmental justice concerns as compared to the baseline.

The risk analysis indicated that the number of people within 10 km of a facility exposed to risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions (Table 8 of this preamble) is reduced from 2.8 million people in the baseline to approximately 2.7 million people after implementation of the HON controls required by this final action. The populations with a cancer risk greater than or equal to 1-in-1 million resulting from SOCMI source category emissions are located around 111 facilities for both the baseline and post-control.

The post-control population living within 10 km of a facility with estimated cancer risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions (Table 8 of this preamble) has similar demographic percentages to the baseline population with risks greater than or equal to 1-in-1 million. However, the number of individuals with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions is reduced in each demographic. Specifically, the percentage of the population with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions that is Black remains high at 25 percent in the post-control scenario, but the number of Black individuals with risks at or above 1-in-1 million is reduced by over 25,000 people from 692,000 in the baseline to 664,000 in the post-control scenario.

Similarly, the percentage of the population with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions that is Hispanic/Latino is almost twice the national average in the post-control scenario (35 percent versus 19 percent), but the number of Hispanic/Latino individuals with risks at or above 1-in-1 million is reduced by about 24,000 people from 958,000 in the baseline to 934,000 in the post-control scenario.

The percent of the population that is American Indian or Alaska Native with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions (0.2 percent) is below the national average (0.7 percent) in the post-control analysis. Nevertheless, there are seven facilities post-control with risks greater than or equal to 1-in-1 million with a percent American Indian or Alaska Native population that is more than 2 times the national average. However, the number of American Indians or Alaska Natives with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions is reduced from 6,000 in the baseline to 5,000 in the post-control scenario.

The percent of the population below the poverty level is the same in the post-control scenario as in the baseline (18 percent), but the number of individuals with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions that are below the poverty level is reduced by 20,000, from 513,000 to 493,000. The percent of individuals over 25 years old without a high school diploma is the same in the post-control scenario as in the baseline (20 percent), but the number of individuals with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions is reduced by almost 23,000, from 561,000 to 538,000. The percentage of the population that is in linguistic isolation with risks greater than or equal to 1-in-1 million resulting from SOCMI source category emissions is the same in the post-control scenario (8 percent), but the number of individuals is reduced by almost 8,000 compared to the baseline, from 228,000 to 220,000.

The risk analysis indicated that the number of people living within 10 km of a facility and exposed to risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions (Table 9 of this preamble) is reduced significantly from 322,000 people in the baseline to 29,000 after implementation of the controls required by this final action. This represents more than a 90 percent reduction in the number of individuals with risk greater than or equal to 50-in-1 million when compared to the baseline. The populations living within 10 km of a facility and with a cancer risk greater than or equal to 50-in-1 million resulting from SOCMI source category emissions are located around 13 facilities in the post-control scenario, 8 fewer facilities than in the baseline. These 13 facilities are located in Alabama, Arkansas, Illinois, Kentucky, Louisiana (5 facilities), and Texas (4 facilities). The communities within 10 km of five of those facilities (in Texas (3 facilities), Alabama, and Illinois) comprise 95 percent of the population with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions.

The number of individuals with risks greater than or equal to 50-in-1 million is reduced significantly for each demographic category in the post-control scenario. Specifically, the percentage of the population with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions that is Black decreased in the post-control scenario and is equal to the national average (12 percent). The number of Black individuals with risks at or above 50-in-1 million is reduced from 59,000 in the baseline to 4,000 post-control. The percentage of the population with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions that is Hispanic/Latino increased from 25 percent in the baseline to 29 percent post-control, but the number of Hispanic/Latino individuals with risks at or above 50-in-1 million is reduced from 81,000 in the baseline to 9,000 post-control.

Overall, the percent of the population that is American Indian or Alaska Native with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions (0.3 percent) is well below the national average (0.7 percent) in the post-control scenario. In addition, the number of American Indians or Alaska Natives with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions is reduced from 600 in the baseline to less than 100 post-control.

The percent of the population with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions whose income is below the poverty level (11 percent) is reduced from the baseline (15 percent) post-control. In addition, the number of individuals with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions who are below the poverty level is reduced from 47,000 to 3,000. The number of individuals with risks greater than or equal to 50-in-1 million resulting from SOCMI source category emissions that are over 25 years old without a high school diploma or are linguistically isolated are also greatly reduced post-control.

The risk analysis indicated that the number of people living within 10 km of a facility with risks greater than 100-in-1 million resulting from SOCMI source category emissions (Table 10 of this preamble) is reduced from 83,000 individuals in the baseline to zero individuals after application of the SOCMI controls required by this final action. Therefore, for the post-control risk-based demographic results, there are no greater than 100-in-1 million demographic results to discuss.

In summary, as shown in the post-control risk-based demographic analysis, the controls required by this final action significantly reduce the number of people expected to have cancer risks greater than or equal to 1-in-1 million, greater than or equal to 50-in-1 million, and greater than 100-in-1 million resulting from SOCMI source category emissions. Although the number of individuals with risks greater than or equal to 1-in-1 million is reduced in the post-control scenario (reduced from 2.8 million people to 2.7 million people), populations of Black individuals, Hispanic/Latino individuals, those living below the poverty level, and those over 25 without a high school diploma remain disproportionately represented. Similarly, the number of individuals with risks greater than or equal to 50-in-1 million is reduced significantly in the post-control scenario (reduced from 322,000 to 29,000), but the population of Black individuals remains disproportionately represented. Post-control, there are no individuals with risks greater than 100-in-1 million resulting from SOCMI source category emissions (reduced from 83,000 people to 0 people).

2. HON Whole-Facility Demographics

As described in Section III.A.5 of this preamble, we assessed the facility-wide (or “whole-facility”) risks for 195 HON facilities in order to compare the SOCMI source category risk to the whole-facility risks, accounting for HAP emissions from the entire major source and not just those resulting from SOCMI source category emissions at the major source as discussed in the previous section. The whole-facility risk analysis includes all sources of HAP emissions at each facility as reported in the NEI (described in section III.C of the preamble to the proposed rule). Since HON facilities tend to include HAP emissions sources from many source categories, the EPA conducted a whole-facility demographic analysis focused on post-control risks. This whole-facility demographic analysis characterizes the remaining risks communities face after implementation of the controls required in this final action for both the SOCMI source category and the Neoprene Production source category.

The whole-facility demographic analysis is an assessment of individual demographic groups in the total population living within 10 km (~6.2 miles) and 50 km (~31 miles) of the facilities. In this preamble, we focus on the 10 km radius for the demographic analysis because, based on SOCMI category emissions, this distance includes all the facility MIR locations, includes 97 percent of the population with cancer risks greater than or equal to 50-in-1 million, and includes 100 percent of the population with risks greater than 100-in-1 million. The results of the whole-facility demographic analysis for populations living within 50 km are included in the document titled Analysis of Demographic Factors for Populations Living Near Hazardous Organic NESHAP (HON) Operations: Whole Facility Analysis—Final, which is available in the docket for this rulemaking.

The whole-facility demographic analysis post-control results are shown in Table 11 of this preamble. This analysis focused on the populations living within 10 km of the HON facilities with estimated whole-facility post-control cancer risks greater than or equal to 1-in-1 million, greater than or equal to 50-in-1 million, and greater than 100-in-1 million. The risk analysis indicated that all emissions from the HON facilities, after the reductions imposed by the final rule, expose a total of about 3 million people living around 140 facilities to a cancer risk greater than or equal to 1-in-1 million, 79,000 people living around 24 facilities to a cancer risk greater than or equal to 50-in-1 million, and 2,900 people living around 4 facilities to a cancer risk greater than 100-in-1 million.

When the HON whole-facility populations are compared to the SOCMI source category populations in the post-control scenarios, we see 400,000 additional people with risks greater than or equal to 1-in-1 million, 50,000 additional people with risks greater than or equal to 50-in-1 million, and 2,900 additional people with risks greater than 100-in-1 million. With the exception of a smaller percentage of affected Hispanic/Latino individuals (35 percent for category versus 33 percent whole-facility), the demographic distribution of the whole-facility population with risks greater than or equal to 1-in-million is similar to the source category population with risks greater than or equal to 1-in-1 million in the post-control scenario. The population with risks greater than or equal to 50-in-1 million in the whole-facility analysis has a lower percent of Hispanic/Latino individuals than the category population with risks greater than or equal to 50-in-1 million (25 percent versus 29 percent). The percentage of the population with risks greater than or equal to 50-in-1 million that is below the poverty level or over 25 years old without a high school diploma is higher for the whole-facility post-control population than for the category post-control population (14 percent versus 11 percent). The SOCMI source category emissions analysis indicated that there are no people with post-control risks greater than 100-in-1 million. Based on results from the whole-facility emissions analysis, there are 2,900 people with post-control risks greater than 100-in-million. The increased cancer risk for most of these 2,900 people is driven by EtO emissions from non-HON processes and whole-facility emissions from the neoprene production facility (a combination of the remaining SOCMI category risk and Neoprene Production category risk at this facility). The percent of the population in the whole-facility analysis with post-control risks greater than 100-in-1 million that is Black (25 percent, 700 individuals) is well above the national average (12 percent). In addition, the percent of the population in the whole-facility analysis with a post control risk greater than 100-in-1 million that is below the poverty level (22 percent, 600 individuals), and the percent of the population that is over 25 years old without a high school diploma (27 percent, 800 individuals) are above the national average (13 percent and 12 percent, respectively). We note that as further discussed in section IV.B of this preamble, the EPA is finalizing a fenceline action level of 0.2 µg/m³ for EtO for the whole-facility. As such, we believe that once fenceline monitoring is fully implemented, that whole-facility post-control risks will be lower and the number of people presented in Table 11 of this preamble at each risk threshold will be lower.

3. Neoprene Production Source Category Demographics

For the Neoprene Production source category subject to the P&R I NESHAP, the EPA examined the potential for the one neoprene production facility to pose environmental justice concerns to communities both in the baseline and under the control option required in this final action. Specifically, the EPA analyzed how demographics and risk are distributed both pre- and post-controls. The methodology and detailed results of the demographic analysis are presented in a technical report, Analysis of Demographic Factors for Populations Living Near Neoprene Production Operations—Final, which is available in the docket for this rulemaking.

To examine the potential for environmental justice concerns in the pre-control baseline, the EPA conducted three different demographic analyses: a baseline proximity analysis, baseline cancer risk-based analysis, and post-control cancer risk-based analysis. These analyses (total baseline, baseline risk, and post-control risks) assessed the demographic groups in the populations living within 5 km (~3.1 miles) and 50 km (~31 miles) of the facility. For the Neoprene Production source category, we focus on the 5 km radius for the demographic analysis because it encompasses the facility MIR location and captures 100 percent of the population with cancer risks resulting from Neoprene Production source category emissions greater than or equal to 50-in-1 million and greater than 100-in-1 million. The results of the proximity analysis for populations living within 50 km are included in the technical report included in the docket for this final action. Nationwide average demographics data are provided as a frame of reference.

The results of the proximity demographic analysis indicate that a total of about 29,000 people live within 5 km of the Neoprene facility. The percent of the population that is Black is more than four times the national average. The percent of people living below the poverty level is almost double the national average.

The baseline risk-based demographic analysis indicates that Black individuals are disproportionally overrepresented at all cancer risk levels resulting from Neoprene Production source category emissions (percent of Black individuals range from 5 to 7 times the national average percent). The percent of the population that is below the poverty level is twice the national average within 5 km of the Neoprene facility.

The post-control risk-based demographic analysis indicates that the controls required for Neoprene Production source category in this final action do not reduce the number of people with cancer risks resulting from Neoprene Production source category emissions greater than or equal to 1-in-1 million at the 5 km distance. However, the controls do significantly reduce the number of people with risks resulting from Neoprene Production source category emissions greater than or equal to 1-in-1 million within 50 km. The populations with risks resulting from Neoprene Production source category emissions greater than or equal to 50-in-1 million and greater than 100-in-1 million are reduced at all distances by more than 88 percent by the controls for the Neoprene Production source category under consideration. In the post-control scenario, there are no people with risks resulting from Neoprene Production source category emissions greater than 100-in-1 million.

a. Baseline Proximity Analysis

The column titled “Total Population Living within 5 km of Neoprene Facility” in Tables 12 through 14 of this preamble shows the demographics for the total population living within 5 km (~3.1 miles) of the neoprene facility. A total of about 29,000 people lives within 5 km of the one neoprene facility. The results of the proximity demographic analysis indicate that the percentage of the population that is Black (56 percent, 16,000 people) is more than four times the national average (12 percent). The percentage of people living below the poverty level (23 percent, 6,500 people) and those over the age of 25 without a high school diploma (16 percent, 4,500 people) are higher than the national averages (13 percent and 12 percent, respectively). The baseline proximity analysis indicates that the proportion of other demographic groups living within 5 km of the neoprene facility is similar to or below the national average.

b. Baseline Risk-Based Demographics

The baseline risk-based demographic analysis results are shown in the “baseline” column of Tables 12 through 14 of this preamble. This analysis focused on the populations living within 5 km (~3.1 miles) of the neoprene facility with estimated cancer risks resulting from Neoprene Production source category emissions greater than or equal to 1-in-1 million (Table 12 of this preamble), greater than or equal to 50-in-1 million (Table 13 of this preamble), and greater than 100-in-1 million (Table 14 of this preamble) in the absence of the reductions we are finalizing in this action.

In the baseline, emissions from the Neoprene Production source category expose all individuals within 5 km of the facility (29,000 people) to a cancer risk greater than or equal to 1-in-1 million. Since the entire population within 5 km are exposed to risks greater than or equal to 1-in-1 million, the demographics of the baseline at-risk population are the same as the total baseline population. Specifically, a high percentage of the population is Black (56 percent versus 12 percent nationally), below the poverty line (23 percent versus 13 percent nationally), and over the age of 25 without a high school diploma (16 percent versus 12 percent nationally). The percentages of other demographic groups within the population with risks resulting from Neoprene Production source category emissions greater than or equal to 1-in-1 million living within 5 km of the neoprene facility are similar to or below the national average. Within 50 km (~31 miles) of the facility, about 70 percent of the population (687,000 people of the 1 million total within 50 km) is exposed to a cancer risk resulting from Neoprene Production source category emissions greater than or equal to 1-in-1 million. Additional details on the 50 km results can be found in the demographics report located in the docket.

The risk-based demographics analysis indicates that emissions from the source category, prior to the reductions we are finalizing in this action, expose about 13,000 individuals within 5 km of the facility to a cancer risk greater than or equal to 50-in-1 million (about half of the total population within 5 km). As seen at the lower risk level of greater than or equal to 1-in-1 million, the population with risks greater than or equal to 50-in-1 million has a very high percentage of Black individuals; that percent is almost 6 times the national average (68 percent versus 12 percent nationally). The percentage of the population that is below the poverty line is more than double the national average (27 percent versus 13 percent nationally), and the percentage of the population that is over the age of 25 without a high school diploma is 1.5 times the national average (18 percent versus 12 percent nationally). The percentages of other demographic groups within the population with risks resulting from Neoprene Production source category emissions greater than or equal to 50-in-1 million living within 5 km of the Neoprene facility are similar to or below the national average.

In the baseline, there are 2,000 people living within 5 km of the Neoprene facility with a cancer risk greater than 100-in-1 million resulting from Neoprene Production source category emissions. The percent of the population that is Black with baseline cancer risk greater than 100-in-1 million (85 percent, 1,750 people) is over 7 times the national average (12 percent). The percentage of the population with cancer risks greater than 100-in-1 million that is below the poverty level (31 percent, 600 people) is about 2.5 times the national average (13 percent). The percent of the population that is over 25 without a high school diploma (14 percent, 300 people) is just above the national average (12 percent).

In summary, the baseline risk-based demographic analysis, which focuses on those specific locations that are expected to have higher cancer risks in the baseline, indicates that Black individuals are disproportionally overrepresented at all cancer risk levels. Specifically, at all risk levels, the percent of the population that is Black is 5 to 7 times the national average and the percent of the population that is below the poverty level is twice the national average within 5 km of the neoprene production facility.

c. Post-Control Risk-Based Demographics

This analysis focused on the populations living within 5 km (~3.1 miles) of the facility with estimated cancer risks resulting from Neoprene Production source category emissions greater than or equal to 1-in-1 million (Table 12 of this preamble), greater than or equal to 50-in-1 million (Table 13 of this preamble), and greater than 100-in-1 million (Table 14 of this preamble) after implementation of the Neoprene Production source category control options as described in section III.B.2.b of this preamble. The results of the post-control risk-based demographics analysis are in the columns titled “Post-Control” of Tables 12 through 14 of this preamble. In this analysis, we evaluated how all of the controls required by this final action and emission reductions for the Neoprene Production source category described in this action affect the distribution of risks. This makes it possible to characterize the post-control risks and to evaluate whether the final action creates or mitigates potential environmental justice concerns as compared to the baseline.

The risk analysis indicated that the number of people exposed to risks resulting from Neoprene Production source category emissions greater than or equal to 1-in-1 million within 5 km of the facility (Table 12 of this preamble) is unchanged from the baseline (29,000 people). Therefore, the population living within 5 km of the facility with estimated cancer risks greater than or equal to 1-in-1 million in the post-control scenario (Table 12 of this preamble) has the same demographic percentages as the total population in the proximity analysis and the population with risks greater than or equal to 1-in-1 million in the baseline risk analysis. Specifically, the percentage of the population with risks resulting from Neoprene Production source category emissions in the post-control analysis that is greater than or equal to 1-in-1 million and is Black (56 percent) is almost 5 times the national average (12 percent), and the percent below the poverty level (23 percent) is almost 2 times the national average (13 percent). However, after control, the number of people exposed to risk greater than or equal to 1-in-1 million within 50 km (~31 miles) of the facility is significantly reduced from 687,000 to 58,000.

The risk analysis indicated that the number of people living within 5 km of the facility and exposed to risks greater than or equal to 50-in-1 million resulting from Neoprene Production source category emissions (Table 13 of this preamble) is reduced significantly from about 13,000 people in the baseline to 1,450 people after implementation of the controls required by this final action. This represents more than an 88 percent reduction in the size of the populations at risk when compared to the baseline population. The post-control population living within 5 km of the facility with estimated cancer risks greater than or equal to 50-in-1 million for post-control (Table 13 of this preamble) is almost entirely Black (92 percent). The number of Black individuals with risks greater than or equal to 50-in-1 million is reduced from about 9,000 in the baseline to 1,350 people post-control. Similarly, the post-control population with risks greater than or equal to 50-in-1 million has a high percent of people below poverty (33 percent). The number of people with risks greater than or equal 50-in-1 million that are below the poverty level is reduced from 3,400 in the baseline to 500 people post-control.

The risk analysis indicated that the number of people living within 5 km of the facility and exposed to risks greater than 100-in-1 million resulting from Neoprene Production source category emissions (Table 14 of this preamble) is reduced from over 2,000 people in the baseline to zero people after application of the controls required by this final action. Therefore, for the post-control risk-based demographics, there are no people with risks above 100-in-1 million resulting from Neoprene Production source category emissions.

In summary, as shown in the post-control risk-based demographic analysis, the controls required by this final action do not reduce the number of people expected to have cancer risks resulting from Neoprene Production source category emissions greater than or equal to 1-in-1 million at the 5 km distance. The controls do significantly reduce the number of people with risks resulting from Neoprene Production source category emissions greater than or equal to 1-in-1 million within 50 km. In the post-control population with risks greater than or equal to 1-in-1 million, Black individuals and those living below the poverty level remain disproportionately represented. For the populations with risks greater than or equal to 50-in-1 million and greater than 100-in-1 million, the controls under consideration reduce the at-risk populations by more than 88 percent at all distances. In the post-control population with risks greater than or equal to 50-in-1 million, Black individuals and those living below the poverty level remain disproportionately represented. Post-control, there are no people with risks resulting from Neoprene Production source category emissions greater than 100-in-1 million.

4. Neoprene Production Whole-Facility Demographics

We also evaluated the whole-facility post-control risks at the neoprene production facility. The whole-facility post-control risks include all known sources of HAP emissions at the neoprene production facility, not just those from neoprene production processes. This whole-facility demographic analysis provides a more complete picture of the remaining risks at the facility after implementation of the controls required by this final action and the populations exposed to emissions resulting from them. The post-control whole-facility emissions at the neoprene production facility are a combination of the remaining SOCMI source category risk and Neoprene Production source category risk at this facility. Based on whole-facility emissions, there are a total of about 29,000 people living within 5 km (~3.1 miles) with risks greater than or equal to 1-in-1 million after controls, which is unchanged from the baseline. There are 87,000 people within 50 km of the neoprene facility with post-control whole-facility risks greater than or equal to 1-in-1 million, which is a 90 percent reduction of the 891,000 people in the baseline. The population within 5 km with post-control whole-facility risks of greater than or equal to 1-in-1 million is 56 percent Black, and 23 percent are below the poverty level. Based on whole-facility emissions there are a total of about 3,000 people remaining after controls living within 5 km and 50 km of the neoprene facility with risks greater than or equal to 50-in-1 million (a reduction of 82 percent from the baseline of 16,000 people). This population is 81 percent Black and 30 percent below the poverty level. Based on whole-facility emissions, about 300 people with risks greater than 100-in-1 million remain after controls are implemented living within 5 km and 50 km of the neoprene production facility (a reduction of 86 percent from the baseline of 2,300 people). This population is 99 percent Black, and 33 percent are below the poverty level. We note that as further discussed in section IV.B of this preamble, the EPA is finalizing a secondary fenceline action level of 0.3 µg/m³ for chloroprene for the whole-facility. As such, we believe once fenceline monitoring is fully implemented, that whole-facility post-control risks will be reduced to at or below 100-in-1 million and that 0 people (rather than the approximate 300 people as shown in this analysis) will have lifetime cancer risks greater than 100-in-1 million post-control.

The results of the whole-facility demographic analysis for populations living within 50 km are included in the document titled Analysis of Demographic Factors for Populations Living Near Neoprene Production Operations: Whole Facility Analysis—Final, which is available in the docket for this rulemaking.

5. P&R I and P&R II Source Categories Demographics

As stated above, for the P&R I and P&R II NESHAP, other than the Neoprene Production source category within the P&R I NESHAP, we have not conducted a risk analysis for this final action. Therefore, to examine the potential for any environmental justice concerns that might be associated with P&R I (excluding neoprene) or P&R II facilities, we performed a proximity demographic analysis, which is an assessment of individual demographic groups of the populations living within 5 km (~3.1 miles) and 50 km (~31 miles) of the facilities. The EPA then compared the data from this analysis to the national average for each of the demographic groups. In this preamble, we focus on the proximity results for the populations living within 5 km (~3.1 miles) of the facilities. The results of the proximity analysis for populations living within 50 km are included in the document titled Analysis of Demographic Factors for Populations Living Near Polymers and Resins I and Polymer and Resins II Facilities (see Docket Item No. EPA-HQ-OAR-2022-0730-0060).

The results show that for populations within 5 km of the 18 P&R I facilities (5 in Louisiana, 6 in Texas, 2 in Kentucky, one each in Georgia, Minnesota, Mississippi, Ohio, Michigan), the following demographic groups were above the national average: Black individuals (37 percent versus 12 percent nationally), Hispanic/Latino individuals (24 percent versus 19 percent nationally), people living below the poverty level (24 percent versus 13 percent nationally), people over the age of 25 without a high school diploma (21 percent versus 12 percent nationally), and linguistically isolated households (7 percent versus 5 percent nationally).

The results show that for populations within 5 km of the 5 P&R II facilities (2 in Texas, one each in Alabama, Arkansas, Oregon), the following demographic groups were above the national average: American Indian or Alaska Native individuals (0.9 percent versus 0.7 percent nationally), Hispanic/Latino individuals (27 percent versus 19 percent nationally), and people over the age of 25 without a high school diploma (13 percent versus 12 percent nationally).

A summary of the proximity demographic assessment performed is included as Table 15 of this preamble. The methodology and the results of the demographic analysis are presented in the document titled Analysis of Demographic Factors for Populations Living Near Polymers and Resins I and Polymer and Resins II Facilities (see Docket Item No. EPA-HQ-OAR-2022-0730-0060).

6. Proximity Demographics Analysis for NSPS Subpart VVb

In addition, to provide information for the public's understanding, the Agency conducted an analysis of the impacts of the final NSPS subpart VVb on communities with environmental justice concerns. The final NSPS subpart VVb covers VOC emissions from certain equipment leaks in the SOCMI from sources that are constructed, reconstructed, or modified after April 25, 2023.

The locations of the new, modified, and reconstructed sources that will become subject to NSPS subpart VVb are not known. Therefore, to provide information on the potential for any environmental justice issues that might be associated with the final NSPS subpart VVb, we performed a proximity demographic analysis for 575 existing facilities that are currently subject to NSPS subparts VV or VVa. These represent facilities that might modify or reconstruct in the future and become subject to the NSPS subpart VVb requirements. This proximity demographic analysis characterized the individual demographic groups of the populations living within 5 km and within 50 km (~31 miles) of the existing facilities. The EPA then compared the data from this analysis to the national average for each of the demographic groups.

The proximity demographic analysis shows that, within 5 km of the facilities, the percent of the population that is Black is double the national average (24 percent versus 12 percent) (Table 16 of this preamble). The percent of people within 5 km living below the poverty level is significantly higher than the national average (20 percent versus 13 percent). The percent of people living within 5 km that are over 25 without a high school diploma is also higher than the national average (17 percent versus 12 percent). The proximity demographics analysis shows that within 50 km of the facilities, the percent of the population that is Black is above the national average (15 percent versus 12 percent). At 50 km, the remaining percentages for the demographics are similar to or below the national average.

The methodology and the results (including facility-specific results) of the demographic analysis are presented in the document titled Analysis of Demographic Factors for Populations Living Near Existing Facilities Subject to NSPS Subparts VV or VVa (see Docket Item No. EPA-HQ-OAR-2022-0730-0058).

7. Proximity Demographics Analysis for NSPS Subparts IIIa, NNNa, and RRRa

The final NSPS subparts IIIa, NNNa, and RRRa cover VOC emissions from certain process vents in the SOCMI from sources that are constructed, reconstructed, or modified after April 25, 2023.

The locations of the new, modified, and reconstructed sources that will become subject to NSPS subparts IIIa, NNNa, and RRRa are not known. Therefore, to assess the potential for any environmental justice issues that might be associated with the final subparts, we performed a proximity demographic analysis for 266 existing facilities that are currently subject to NSPS subpart III, NNN, or RRR. These facilities represent facilities that might modify or reconstruct in the future and thus become subject to the final NSPS requirements. This proximity demographic analysis characterized the individual demographic groups of the populations living within 5 km (~3.1 miles) and within 50 km (~31 miles) of the existing facilities. The EPA then compared the data from this analysis to the national average for each of the demographic groups.

The proximity demographic analysis shows that, within 5 km of the facilities, the percent of the population that is Black is almost double the national average (23 percent versus 12 percent) (Table 17 of this preamble). In addition, the percentage of the population within 5 km of the facilities that is Hispanic or Latino is also above the national average (23 percent versus 19 percent). The percentage of people within 5 km living below the poverty level is significantly higher than the national average (20 percent versus 13 percent). The percentage of people living within 5 km that are over 25 without a high school diploma is also higher than the national average (17 percent versus 12 percent). The proximity demographics analysis also shows that within 50 km of the facilities, the percentage of the population that is Black is above the national average (18 percent versus 12 percent). At 50 km, the remaining percentages for the demographics are similar to or below the national average.

The methodology and the results (including facility-specific results) of the demographic analysis are presented in the document titled Analysis of Demographic Factors for Populations Living Near Existing Facilities Subject to NSPS Subparts III, NNN, or RRR (see Docket Item No. EPA-HQ-OAR-2022-0730-0059).

G. Children's Environmental Health

This action finalizes standards to address risk from, among other HAP, EtO and chloroprene. In addition, the EPA's Policy on Children's Health also applies to this action. Accordingly, we evaluated the environmental health or safety effects of EtO and chloroprene emissions and exposures on children.

Because EtO and chloroprene are mutagenic ( i.e., it can damage DNA), children are expected to be more susceptible to their harmful effects. To take this into account, as part of the risk assessments in support of this rulemaking, the EPA followed its guidelines and applied age-dependent adjustment factors (ADAFs) for childhood exposures (from birth up to 16 years of age). It should be noted that, because EtO and chloroprene are mutagenic, emission reductions finalized in this action will be particularly beneficial to children. The results of this evaluation are contained in section IV.A of this preamble and further documented in the risk reports, Residual Risk Assessment for the SOCMI Source Category in Support of the 2024 Risk and Technology Review Final Rule and Residual Risk Assessment for the Polymers & Resins I Neoprene Production Source Category in Support of the 2024 Risk and Technology Review Final Rule, which are available in the docket.

VI. Statutory and Executive Order Reviews

Additional information about these statutes and Executive Orders can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 14094: Modernizing Regulatory Review

This action is a “significant regulatory action” as defined under section 3(f)(1) of Executive Order 12866, as amended by Executive Order 14094. Accordingly, the EPA submitted this action to the Office of Management and Budget (OMB) for Executive Order 12866 review. Documentation of any changes made in response to the Executive Order 12866 review is available in the docket. The EPA prepared an economic analysis of the potential impacts associated with this action. This analysis, titled Regulatory Impact Analysis for the Final New Source Performance Standards for the Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I & II Polymers and Resins Industry (EPA-452/R-24-001), is also available in the docket. Table 18 of this preamble summarizes the PV and EAV of total costs and benefits for the final action.

B. Paperwork Reduction Act (PRA)

1. HON

The information collection activities in this rule have been submitted for approval to OMB under the PRA. The information collection request (ICR) document that the EPA prepared has been assigned EPA ICR number 2753.02. You can find a copy of the ICR in the docket for this rule, and it is briefly summarized here. The information collection requirements are not enforceable until OMB approves them.

The EPA is finalizing amendments to the HON that revise provisions pertaining to emissions from flares, PRDs, process vents, storage vessels, pressure vessels, storage vessel degassing, heat exchange systems, maintenance vents, wastewater, and equipment leaks. The EPA is also finalizing additional requirements pertaining to EtO emissions from process vents, storage vessels, heat exchange systems, equipment leaks, and wastewater; and dioxins and furans emissions from process vents. In addition, the EPA is finalizing amendments to the HON that revise provisions pertaining to emissions during periods of SSM, add requirements for electronic reporting of periodic reports and performance test results, fenceline monitoring, carbon adsorbers, and bypass monitoring, and make other minor clarifications and corrections. This information will be collected to assure compliance with the HON.

Respondents/affected entities: Owners or operators of HON facilities.

Respondent's obligation to respond: Mandatory (40 CFR part 63, subparts F, G, H, and I).

Estimated number of respondents: 209 (assumes two new respondents over the next 3 years).

Frequency of response: Initially, quarterly, semiannually, and annually.

Total estimated burden: average annual recordkeeping and reporting burden is 83,500 hours (per year) to comply with the final amendments in HON. Burden is defined at 5 CFR 1320.3(b).

Total estimated cost: average annual cost is $66,000,000 (per year) which includes $57,500,000 annualized capital and operations and maintenance costs, to comply with the final amendments in HON.

An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB control number. The OMB control numbers for the EPA's regulations in 40 CFR are listed in 40 CFR part 9. When OMB approves this ICR, the Agency will announce that approval in the Federal Register and publish a technical amendment to 40 CFR part 9 to display the OMB control number for the approved information collection activities in this final rule.

2. P&R I NESHAP

The information collection activities in this rule have been submitted for approval to OMB under the PRA. The ICR document that the EPA prepared has been assigned EPA ICR number 2410.07. You can find a copy of the ICR in the docket for this rule, and it is briefly summarized here. The information collection requirements are not enforceable until OMB approves them.

The EPA is finalizing amendments to the P&R I NESHAP that revise provisions pertaining to emissions from flares, PRDs, continuous process vents, batch process vents, storage vessels, pressure vessels, storage vessel degassing, heat exchange systems, maintenance vents, wastewater, and equipment leaks. The EPA is also finalizing requirements pertaining to: chloroprene emissions from process vents, storage vessels, and wastewater; and dioxins and furans emissions from continuous process vents and batch process vents. In addition, the EPA is finalizing amendments to the P&R I NESHAP that revise provisions pertaining to emissions during periods of SSM, add requirements for electronic reporting of periodic reports and performance test results, fenceline monitoring, carbon adsorbers, and bypass monitoring, and make other minor clarifications and corrections. This information will be collected to assure compliance with the P&R I NESHAP.

Respondents/affected entities: Owners or operators of P&R I facilities.

Respondent's obligation to respond: Mandatory (40 CFR part 63, subpart U).

Estimated number of respondents: 19 (assumes no new respondents over the next 3 years).

Frequency of response: Initially, quarterly, semiannually, and annually.

Total estimated burden: average annual recordkeeping and reporting burden is 8,126 hours (per year) to comply with the final amendments in the P&R I NESHAP. Burden is defined at 5 CFR 1320.3(b).

Total estimated cost: average annual cost is $3,200,000 (per year) which includes $2,370,000 annualized capital and operations and maintenance costs, to comply with the final amendments in the P&R I NESHAP.

An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB control number. The OMB control numbers for the EPA's regulations in 40 CFR are listed in 40 CFR part 9. When OMB approves this ICR, the Agency will announce that approval in the Federal Register and publish a technical amendment to 40 CFR part 9 to display the OMB control number for the approved information collection activities in this final rule.

3. P&R II NESHAP

The information collection activities in this rule have been submitted for approval to OMB under the PRA. The ICR document that the EPA prepared has been assigned EPA ICR number 1681.12. The OMB Control Number is 2060-0290. You can find a copy of the ICR in the docket for this rule, and it is briefly summarized here. The information collection requirements are not enforceable until OMB approves them.

The EPA is finalizing amendments to the P&R II NESHAP to add requirements pertaining to: heat exchange systems, PRDs, dioxins and furans emissions from process vents, and maintenance vents. In addition, the EPA is finalizing amendments to the P&R II NESHAP that revise provisions pertaining to emissions during periods of SSM, add requirements for electronic reporting of periodic reports and performance test results, and make other minor clarifications and corrections. This information will be collected to assure compliance with the P&R II NESHAP.

Respondents/affected entities: Owners or operators of P&R II facilities.

Respondent's obligation to respond: Mandatory (40 CFR part 63, subpart W).

Estimated number of respondents: 5 (assumes no new respondents over the next 3 years).

Frequency of response: Initially, semiannually, and annually.

Total estimated burden: average annual recordkeeping and reporting burden is 202 hours (per year) to comply with the final amendments in the P&R II NESHAP. Burden is defined at 5 CFR 1320.3(b).

Total estimated cost: average annual cost is $1,780,000 (per year) which includes $1,760,000 annualized capital and operations and maintenance costs, to comply with the final amendments in the P&R II NESHAP.

An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB control number. The OMB control numbers for the EPA's regulations in 40 CFR are listed in 40 CFR part 9. When OMB approves this ICR, the Agency will announce that approval in the Federal Register and publish a technical amendment to 40 CFR part 9 to display the OMB control number for the approved information collection activities in this final rule.

4. NSPS Subparts VV, VVa, III, NNN, and RRR

This action does not impose any new information collection burden under the PRA for NSPS subparts VV, VVa, III, NNN, and RRR. OMB has previously approved the information collection activities contained in the existing regulations and has assigned OMB Control number 2060-0443 for 40 CFR part 60 subparts VV, VVa, III, NNN, and RRR (this one OMB Control number is for the Consolidated Federal Air Rule in 40 CFR part 65 which presents the burden for complying with 40 CFR part 65, but also presents the burden for facilities complying with each individual subpart). This action is believed to result in no changes to the information collection requirements of these NSPS, so that the information collection estimate of project cost and hour burden from these NSPS have not been revised.

5. NSPS Subpart VVb

The information collection activities in this rule have been submitted for approval to OMB under the PRA. The ICR document that the EPA prepared has been assigned EPA ICR number 2755.02. You can find a copy of the ICR in the docket for this rule, and it is briefly summarized here. The information collection requirements are not enforceable until OMB approves them.

The EPA is finalizing in a new NSPS subpart VVb the same requirements in NSPS subpart VVa plus requiring that all gas/vapor and light liquid valves be monitored monthly at a leak definition of 100 ppm and all connectors be monitored once every 12 months at a leak definition of 500 ppm. In addition, the EPA is finalizing the removal of SSM provisions (the standards apply at all times), additional requirements for electronic reporting of periodic reports, and other minor clarifications and corrections. This information will be collected to assure compliance with the NSPS subpart VVb.

Respondents/affected entities: Owners or operators of certain equipment leaks in the SOCMI.

Respondent's obligation to respond: Mandatory (40 CFR part 60, subpart VVb).

Estimated number of respondents: 36 (assumes 36 new respondents over the next 3 years).

Frequency of response: Initially, occasionally, and annually.

Total estimated burden: average annual recordkeeping and reporting burden is 5,414 hours (per year) to comply with all of the requirements in the NSPS. Burden is defined at 5 CFR 1320.3(b).

Total estimated cost: average annual cost is $3,600,000 (per year) which includes $3,050,000 annualized capital and operations and maintenance costs, to comply with all of the requirements in the NSPS.

An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB control number. The OMB control numbers for the EPA's regulations in 40 CFR are listed in 40 CFR part 9. When OMB approves this ICR, the Agency will announce that approval in the Federal Register and publish a technical amendment to 40 CFR part 9 to display the OMB control number for the approved information collection activities in this final rule.

6. NSPS Subpart IIIa

The information collection activities in this rule have been submitted for approval to OMB under the PRA. The ICR document that the EPA prepared has been assigned EPA ICR number 2756.02. You can find a copy of the ICR in the docket for this rule, and it is briefly summarized here. The information collection requirements are not enforceable until OMB approves them.

The EPA is finalizing requirements for new, modified, or reconstructed sources as follows: require owners and operators reduce emissions of TOC (minus methane and ethane) from all vent streams of an affected facility (and not including the alternative of maintaining a TRE index value greater than 1 without the use of a control device); require standards apply at all times (including during SSM periods); revise monitoring requirements for flares; add maintenance vent requirements; revise requirements for adsorber monitoring; exclude the relief valve discharge exemption such that any relief valve discharge to the atmosphere of a vent stream is a violation of the emissions standard; and prohibit an owner or operator from bypassing the control device at any time, and to report any such violation. This information will be collected to assure compliance with the NSPS subpart IIIa.

Respondents/affected entities: Owners or operators of air oxidation unit processes in the SOCMI.

Respondent's obligation to respond: Mandatory (40 CFR part 60, subpart IIIa).

Estimated number of respondents: 6 (assumes 6 new respondents over the next 3 years).

Frequency of response: Initially, semiannually, and annually.

Total estimated burden: average annual recordkeeping and reporting burden is 275 hours (per year) to comply with all of the requirements in NSPS subpart IIIa. Burden is defined at 5 CFR 1320.3(b).

Total estimated cost: average annual cost is $4,280,000 (per year) which includes $4,250,000 annualized capital and operations and maintenance costs, to comply with all of the requirements in NSPS subpart IIIa.

An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB control number. The OMB control numbers for the EPA's regulations in 40 CFR are listed in 40 CFR part 9. When OMB approves this ICR, the Agency will announce that approval in the Federal Register and publish a technical amendment to 40 CFR part 9 to display the OMB control number for the approved information collection activities in this final rule.

7. NSPS Subpart NNNa

The information collection activities in this rule have been submitted for approval to OMB under the PRA. The ICR document that the EPA prepared has been assigned EPA ICR number 2757.02. You can find a copy of the ICR in the docket for this rule, and it is briefly summarized here. The information collection requirements are not enforceable until OMB approves them.

The EPA is finalizing requirements for new, modified, or reconstructed sources as follows: require owners and operators reduce emissions of TOC (minus methane and ethane) from all vent streams of an affected facility (and not including the alternative of maintaining a TRE index value greater than 1 without the use of a control device); require the standards apply at all times (including during SSM periods); revise monitoring requirements for flares; add maintenance vent requirements; revise requirements for adsorber monitoring; exclude the relief valve discharge exemption such that any relief valve discharge to the atmosphere of a vent stream is a violation of the emissions standard; and prohibit an owner or operator from bypassing the control device at any time, and to report any such violation. This information will be collected to assure compliance with the NSPS subpart NNNa.

Respondents/affected entities: Owners or operators of distillation operations in the SOCMI.

Respondent's obligation to respond: Mandatory (40 CFR part 60, subpart NNNa).

Estimated number of respondents: 7 (assumes 7 new respondents over the next 3 years).

Frequency of response: Initially, semiannually, and annually.

Total estimated burden: average annual recordkeeping and reporting burden is 320 hours (per year) to comply with all of the requirements in NSPS subpart NNNa. Burden is defined at 5 CFR 1320.3(b).

Total estimated cost: average annual cost is $4,990,000 (per year) which includes $4,960,000 annualized capital and operations and maintenance costs, to comply with all of the requirements in NSPS subpart NNNa.

An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB control number. The OMB control numbers for the EPA's regulations in 40 CFR are listed in 40 CFR part 9. When OMB approves this ICR, the Agency will announce that approval in the Federal Register and publish a technical amendment to 40 CFR part 9 to display the OMB control number for the approved information collection activities in this final rule.

8. NSPS Subpart RRRa

The information collection activities in this rule have been submitted for approval to OMB under the PRA. The ICR document that the EPA prepared has been assigned EPA ICR number 2759.02. You can find a copy of the ICR in the docket for this rule, and it is briefly summarized here. The information collection requirements are not enforceable until OMB approves them.

The EPA is finalizing requirements for new, modified, or reconstructed sources as follows: require owners and operators reduce emissions of TOC (minus methane and ethane) from all vent streams of an affected facility (and not including the alternative of maintaining a TRE index value greater than 1 without the use of a control device); require the standards apply at all times (including during SSM periods); revise monitoring requirements for flares; add maintenance vent requirements; revise requirements for adsorber monitoring; exclude the relief valve discharge exemption such that any relief valve discharge to the atmosphere of a vent stream is a violation of the emissions standard; and prohibit an owner or operator from bypassing the control device at any time, and to report any such violation. This information will be collected to assure compliance with the NSPS subpart RRRa.

Respondents/affected entities: Owners or operators of reactor processes in the SOCMI.

Respondent's obligation to respond: Mandatory (40 CFR part 60, subpart RRRa).

Estimated number of respondents: 6 (assumes 6 new respondents over the next 3 years).

Frequency of response: Initially, semiannually, and annually.

Total estimated burden: average annual recordkeeping and reporting burden is 275 hours (per year) to comply with all of the requirements in NSPS subpart RRRa. Burden is defined at 5 CFR 1320.3(b).

Total estimated cost: average annual cost is $4,280,000 (per year) which includes $4,250,000 annualized capital and operations and maintenance costs, to comply with all of the requirements in NSPS subpart RRRa.

An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB control number. The OMB control numbers for the EPA's regulations in 40 CFR are listed in 40 CFR part 9. When OMB approves this ICR, the Agency will announce that approval in the Federal Register and publish a technical amendment to 40 CFR part 9 to display the OMB control number for the approved information collection activities in this final rule.

C. Regulatory Flexibility Act (RFA)

I certify that each of the final rules in this action will not have a significant economic impact on a substantial number of small entities under the RFA. The small entities subject to the requirements of this action are small businesses. For the final amendments to the HON, the Agency has determined that all small entities affected by this action, estimated to be 9, may experience an average impact of costs being less than 0.5 percent of revenues, not including product recovery, or about 0.43 percent, including product recovery from compliance. Two of these nine entities experienced costs above one percent of revenues, neither had costs exceeding three percent of revenues and represent a small total number of impacted entities. For the final amendments to the P&R I NESHAP, one small entity is impacted and its impact is costs less than 0.5 percent of revenues. For the final amendments to the P&R II NESHAP, no small entities are impacted. Details of the analysis for each final rule including the NSPS that are included in this final action are presented in the RIA for this action, which is found in the docket.

D. Unfunded Mandates Reform Act (UMRA)

This action does not contain an unfunded mandate of $100 million or more (adjusted for inflation) as described in UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect small governments. The costs involved in this action are estimated not to exceed $100 million or more (adjusted for inflation) in any one year.

E. Executive Order 13132: Federalism

This action does not have federalism implications. It will not have substantial direct effects on the states, on the relationship between the national government and the states, or on the distribution of power and responsibilities among the various levels of government.

F. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

This action does not have tribal implications as specified in Executive Order 13175. None of the facilities that have been identified as being affected by this action are owned or operated by tribal governments or located within tribal lands. Thus, Executive Order 13175 does not apply to this action.

G. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks

Executive Order 13045 directs federal agencies to include an evaluation of the health and safety effects of the planned regulation on children in federal health and safety standards and explain why the regulation is preferable to potentially effective and reasonably feasible alternatives. This action is subject to Executive Order 13045 because it is a significant regulatory action under section 3(f)(1) of Executive Order 12866, and the EPA believes that the environmental health or safety risk addressed by this action may have a disproportionate effect on children. This is because EtO and chloroprene, which are HAP emitted by sources subject to this action, are mutagenic ( i.e., it can damage DNA), and children are presented with higher risks based on the EPA's ADAFs for these HAP. Accordingly, we have evaluated the environmental health or safety effects of EtO and chloroprene emissions on children.

The protection offered by these standards to reduce emissions of EtO and chloroprene accounts for childhood exposures by applying ADAFs to account for greater susceptibility of children to these HAP. The results of this evaluation are contained in section IV.A of this preamble and further documented in the risk reports, Residual Risk Assessment for the SOCMI Source Category in Support of the 2024 Risk and Technology Review Final Rule and Residual Risk Assessment for the Polymers & Resins I Neoprene Production Source Category in Support of the 2024 Risk and Technology Review Final Rule, which are available in the docket. This action is preferred over other regulatory options because a residual risk assessment was performed and options were assessed and finalized to reduce emissions of EtO and chloroprene, which will be extremely beneficial to children. Furthermore, EPA's Policy on Children's Health also applies to this action. Information on how the Policy was applied is available under “Children's Environmental Health” in the Supplementary Information section of this preamble.

H. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use

This action is not a “significant energy action” because it is not likely to have a significant adverse effect on the supply, distribution, or use of energy. The EPA expects this final action would not reduce crude oil supply, fuel production, coal production, natural gas production, or electricity production. We estimate that this final action would have minimal impact on the amount of imports or exports of crude oils, condensates, or other organic liquids used in the energy supply industries. Given the minimal impacts on energy supply, distribution, and use as a whole nationally, no significant adverse energy effects are expected to occur. For more information on these estimates of energy effects, please refer to the economic impact analysis contained in the RIA for this final rulemaking.

I. National Technology Transfer and Advancement Act (NTTAA) and 1 CFR Part 51

This action involves technical standards. As discussed in the proposal preamble (88 FR 25080, April 25, 2023), the EPA conducted searches for the HON and the P&R I and P&R II NESHAP through the Enhanced National Standards Systems Network Database managed by the American National Standards Institute (ANSI). We also conducted a review of voluntary consensus standards (VCS) organizations and accessed and searched their databases. We conducted searches for EPA Methods 1, 1A, 2, 2A, 2C, 2D, 2F, 2G, 3B, 4, 18, 21, 22, 25A, 25D, 26, 26A, 27 of 40 CFR part 60, Appendix A, 301, 305, 316 and 320 of 40 CFR part 63, Appendix A, 624, 625, 1624, and 1625 of 40 CFR part 136 Appendix A, 624.1 of 40 CFR part 163, Appendix A. During the EPA's VCS search, if the title or abstract (if provided) of the VCS described technical sampling and analytical procedures that are similar to the EPA's reference method, the EPA ordered a copy of the standard and reviewed it as a potential equivalent method. We reviewed all potential standards to determine the practicality of the VCS for this rule. This review requires significant method validation data that meet the requirements of EPA Method 301 for accepting alternative methods or scientific, engineering, and policy equivalence to procedures in the EPA referenced methods. The EPA may reconsider determinations of impracticality when additional information is available for particular VCS. No applicable voluntary consensus standards were identified for EPA Methods 1, 1A, 2, 2A, 2C, 2D, 2F, 2G, 21, 22, 25D, 27, 305, 316, 624, 624.1, 625, 1624 and 1625.

The EPA incorporates by reference VCS ANSI/ASME PTC 19.10-1981—Part 10, “Flue and Exhaust Gas Analyses” as an acceptable alternative to EPA Method 3B (referenced in NSPS subparts IIIa, NNNa, RRR, and RRRa, and NESHAP subpart G) for the manual procedures only and not the instrumental procedures. This method is used to quantitatively determine the gaseous constituents of exhausts including oxygen, CO₂, carbon monoxide, nitrogen, sulfur dioxide, sulfur trioxide, nitric oxide, nitrogen dioxide, hydrogen sulfide, and hydrocarbons. The ANSI/ASME PTC 19.10-1981—Part 10 method incorporates both manual and instrumental methodologies for the determination of oxygen content. The manual method segment of the oxygen determination is performed through the absorption of oxygen. This method is available at the ANSI, 1899 L Street NW, 11th Floor, Washington, DC 20036 and the American Society of Mechanical Engineers (ASME), Three Park Avenue, New York, NY 10016-5990; telephone number: 1-800-843-5990; and email address: customercare@asme.org. See https://wwww.ansi.org and https://www.asme.org . The standard is available to everyone at a cost determined by ANSI/ASME ($96). ANSI/ASME also offer memberships or subscriptions for reduced costs. The cost of obtaining these methods is not a significant financial burden, making the methods reasonably available.

The EPA incorporates by reference VCS ASTM D6420-18, “Standard Test Method for Determination of Gaseous Organic Compounds by Direct Interface Gas Chromatography-Mass Spectrometry” as an acceptable alternative to EPA Method 18 (referenced in NSPS subparts VV, VVa, VVb, III, IIIa, NNN, NNNa, RRR, and RRRa, and NESHAP subparts F, G, H, I, U, and W) with the following caveats. This ASTM procedure uses a direct interface gas chromatograph/mass spectrometer to identify and quantify VOC and has been approved by the EPA as an alternative to EPA Method 18 only when the target compounds are all known and the target compounds are all listed in ASTM D6420 as measurable. ASTM D6420-18 should not be used for methane and ethane because the atomic mass is less than 35; and ASTM D6420 should never be specified as a total VOC method. The ASTM D6420-18 test method employs a direct interface gas chromatograph/mass spectrometer to measure 36 VOC. The test method provides onsite analysis of extracted, unconditioned, and unsaturated (at the instrument) gas samples from stationary sources.

The EPA incorporates by reference VCS ASTM D6348-12 (Reapproved 2020), “Standard Test Method for Determination of Gaseous Compounds by Extractive Direct Interface Fourier Transform Infrared (FTIR) Spectroscopy” as an acceptable alternative to EPA Method 320 (referenced in NESHAP subparts F and U) with caveats requiring inclusion of selected annexes to the standard as mandatory. This ASTM procedure uses an extractive sampling system that routes stationary source effluent to an FTIR spectrometer for the identification and quantification of gaseous compounds. We note that we proposed VCS ASTM D6348-12e1 as an alternative to EPA Method 320; however, since proposal, a newer version of the method (VCS ASTM D6348-12 (Reapproved 2020)) is now available and we have determined it to be equivalent to EPA Method 320 with caveats. The VCS ASTM D6348-12 (Reapproved 2020) method is an extractive FTIR Spectroscopy-based field test method and is used to quantify gas phase concentrations of multiple target compounds in emission streams from stationary sources. When using ASTM D6348-12 (Reapproved 2020), the following conditions must be met: (1) Annexes Al through A8 to ASTM D6348-12 (Reapproved 2020) are mandatory; and (2) in ASTM D6348-12 (Reapproved 2020) Annex A5 (Analyte Spiking Technique), the percent (%) R must be determined for each target analyte (Equation A5.5). In order for the test data to be acceptable for a compound, %R must be 70% ≥ R ≤ 130%. If the %R value does not meet this criterion for a target compound, the test data is not acceptable for that compound and the test must be repeated for that analyte ( i.e., the sampling and/or analytical procedure should be adjusted before a retest). The %R value for each compound must be reported in the test report, and all field measurements must be corrected with the calculated %R value for that compound by using the following equation:

Reported Results = ((Measured Concentration in Stack))/(%R) × 100.

The EPA is also incorporating by reference Quality Assurance Handbook for Air Pollution Measurement Systems, Volume IV: Meteorological Measurements, Version 2.0 (Final), March 2008 (EPA-454/B-08-002). The Quality Assurance Handbook for Air Pollution Measurement Systems; Volume IV: Meteorological Measurements is an EPA developed guidance manual for the installation, operation, maintenance and calibration of meteorological systems including the wind speed and direction using anemometers, temperature using thermistors, and atmospheric pressure using aneroid barometers, as well as the calculations for wind vector data for on-site meteorological measurements. This VCS may be obtained from the EPA's National Service Center for Environmental Publications ( www.epa.gov/nscep ).

The two ASTM methods (ASTM D6420-18 and ASTM D6348-12 (Reapproved 2020)) are available at ASTM International, 1850 M Street NW, Suite 1030, Washington, DC 20036; telephone number: 1-610-832-9500. See https://www.astm.org/ . These standards are available to everyone at a cost determined by the ASTM ($57 and $76, respectively). The ASTM also offers memberships or subscriptions that allow unlimited access to their methods. The cost of obtaining these methods is not a significant financial burden, making the methods reasonably available to stakeholders.

While the EPA identified 13 other VCS as being potentially applicable, the Agency decided not to use them because these methods are impractical as alternatives because of the lack of equivalency, documentation, validation date, and other important technical and policy considerations. The search and review results have been documented and are in the memorandum, Voluntary Consensus Standard Results for National Emission Standards for Hazardous Air Pollutants From the Synthetic Organic Chemical Manufacturing Industry (see Docket Item No. EPA-HQ-OAR-2022-0730-0008).

Under 40 CFR 63.7(f) and 40 CFR 63.8(f), subpart A—General Provisions, a source may apply to the EPA for permission to use alternative test methods or alternative monitoring requirements in place of any required testing methods, performance specifications, or procedures in the final rule or any amendments.

Also, although not considered a VCS, the EPA incorporates by reference, “Purge-And-Trap For Aqueous Samples” (SW-846-5030B), “Volatile, Nonpurgeable, Water-Soluble Compounds by Azeotropic Distillation” (SW-846-5031), and “Volatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS)” (SW-846-8260D) into 40 CFR 63.109(b)(1), (c)(1), (d), and (e) (for HON) and 40 CFR 63.510(b)(1) and (c) (for the P&R I NESHAP); and “Air Stripping Method (Modified El Paso Method) for Determination of Volatile Organic Compound Emissions from Water Sources,” into 40 CFR 63.104(g)(3)(i) and (ii), and 40 CFR 63.104(f)(3)(iv)(D)(1). Method SW-846-5030B can be used as a purge-and-trap procedure for the analysis of volatile organic compounds in aqueous samples and water miscible liquid samples. Method SW-846-5031 can be used for separation of nonpurgeable, water-soluble, and volatile organic compounds in aqueous samples or leachates from solid matrices using azeotropic distillation. Method SW-846-8260D can be used to determine VOCs in a variety of solid waste matrices and is applicable to nearly all types of samples, regardless of water content. The Modified El Paso Method utilizes dynamic or flow-through system for air stripping a sample of water and analyzing the resultant off-gases for VOCs using a common flame ionization detector (FID) analyzer. Each of these methods is used to identify organic HAP in water; however, SW-846-5031, SW-846-8260D, and SW-846-5030B use water sampling techniques and the Modified El Paso Method uses an air stripping sampling technique. The SW-846 methods are reasonably available from the EPA at https://www.epa.gov/hw-sw846 while the Modified El Paso Method is reasonably available from TCEQ at https://www.tceq.texas.gov/assets/public/compliance/field_ops/guidance/samplingappp.pdf .

In addition, because we are moving all HON definitions from NESHAP subparts G and H ( i.e., 40 CFR 63.111 and 40 CFR 63.161, respectively) into the definition section of NESHAP subpart F ( i.e., 40 CFR 63.101), we are incorporating by reference, API Manual of Petroleum Measurement Specifications (MPMS) Chapter 19.2 (API MPMS 19.2), “Evaporative Loss From Floating-Roof Tanks,” Fourth Edition, August 2020 and “Standard Test Method for Vapor Pressure-Temperature Relationship and Initial Decomposition Temperature of Liquids by Isoteniscope” (ASTM D2879-23) into 40 CFR 63.101 (for HON). The API method (API MPMS 19.2) contains methodologies for estimating the total evaporative losses of hydrocarbons from various types of floating-roof tanks. The ASTM method (ASTM D2879-23) addresses the determination of the vapor pressure of one or more organic components in a gas stream. In addition, the EPA is adding new NSPS subpart VVb to part 60 and is allowing the use of:

ASTM D240-19, Standard Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter and ASTM D4809-18, Standard Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter (Precision Method). The ASTM D240-19 method addresses the determination of net heat of combustion of components of liquid hydrocarbon fuels ranging in volatility from that of light distillates to that of residual fuels. The ASTM D4809-18 method is similar to that of ASTM D240-19, though it specifically addresses the determination of net heat of combustion of aviation fuels with high precision. In addition, ASTM D4809-18 can also be used to address the determination of net heat of combustion for a wide range of volatile and non-volatile materials. The EPA currently allows for the use of previous versions of these methods in NSPS subparts VV and VVa for the determination of net heat of combustion of components in a gas stream; therefore, we are allowing the use of the most recent versions of these methods for this same purpose in NSPS subpart VVb.

ASTM D1945-14 (Reapproved 2019), Standard Test Method for Analysis of Natural Gas by Gas Chromatography. This method addresses the determination of the concentration of a component in a gas stream. The EPA currently allows for the use of previous versions of this method in NSPS subparts VV and VVa for the determination of the concentration of a component in a gas stream; therefore, we are allowing the use of the most recent version of this method for this same purpose in NSPS subpart VVb.

ASTM D2879-23, Standard Test Method for Vapor Pressure-Temperature Relationship and Initial Decomposition Temperature of Liquids by Isoteniscope. This method addresses the determination of the vapor pressure of one or more organic components in a gas stream. The EPA currently allows for the use of previous versions of this method in NSPS subparts VV and VVa for the determination of the vapor pressure of one or more organic components in a gas stream; therefore, we are allowing the use of the most recent version of this method for this same purpose in NSPS subpart VVb.

ASTM E168-16 (Reapproved 2023), Standard Practices for General Techniques of Infrared Quantitative Analysis, ASTM E169-16 (Reapproved 2022): Standard Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis, and ASTM E260-96 (Reapproved 2019), Standard Practice for Packed Column Gas Chromatography. The ASTM E168-16 method addresses the determination of the percent VOC content in the process fluid that is contained in or contacts a piece of equipment using infrared analysis. The ASTM E169-16 is similar to ASTM E168-16, though it uses ultraviolet-visible spectrum analysis rather than infrared analysis. Lastly, ASTM E260-96 is similar to ASTM E168-16 and ASTM E169-16, though it uses gas chromatography rather than infrared or ultraviolet-visible spectrum analysis, respectively. The EPA currently allows for the use of previous versions of these methods in NSPS subparts VV and VVa for the determination of the percent VOC content in the process fluid that is contained in or contacts a piece of equipment; therefore, we are allowing the use of these most recent versions of these methods for this same purpose in NSPS subpart VVb.

All of the ASTM methods that we are adding into the HON, the P&R I NESHAP, and NSPS subpart VVb are available at the same address and contact information provided earlier in this section of this preamble. The API method that we are adding into the HON is available at 200 Massachusetts Avenue NW, Suite 1100, Washington, DC 20001-5571; telephone number: 1-202-682-8000. See https://www.apiwebstore.org/standards/19_2 . These standards are available to everyone at a cost determined by the ASTM or API. The ASTM also offers memberships or subscriptions that allow unlimited access to their methods. The cost of obtaining these methods is not a significant financial burden, making the methods reasonably available to stakeholders.

We are also finalizing amendments to 40 CFR part 60, subpart A and 40 CFR part 63, subpart A to address incorporations by reference. We are amending 40 CFR 60.17 and 40 CFR 63.14 to reflect the ANSI, ASTM, EPA SW, and TCEQ methods incorporated by reference. We are also adding 40 CFR 60.485(g)(5) and 40 CFR 60.485a(g)(5) to 40 CFR 60.17—“Incorporations by Reference” paragraph (h)(195) since they were mistakenly not added to 40 CFR 60.17 during the last amendment to this rule.

J. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority Populations and Low-Income Populations and Executive Order 14096: Revitalizing Our Nation's Commitment to Environmental Justice for All

The EPA believes that the human health or environmental conditions that exist prior to this action result in or have the potential to result in disproportionate and adverse human health or environmental effects on communities with environmental justice concerns. For the HON, a total of 9.3 million people live within 10 km (~6.2 miles) of the 195 HON facilities that were assessed for risk. The percentages of the population that are Black (25 percent versus 12 percent) and Hispanic or Latino (22 percent versus 19 percent) are higher than the national averages. The proportion of other demographic groups living within 10 km of HON facilities is similar or lower than the national average. For the Neoprene Production source category, a total of 29,000 people live within 5 km of the one neoprene production facility in the country. The percent of the population that is Black (56 percent versus 12 percent) is substantially higher than the national average. The proportion of other demographic groups living within 10 km of HON facilities is similar or lower than the national average. The EPA also conducted a risk assessment of possible cancer risks and other adverse health effects, and found that prior to this final rule, cancer risks were above acceptable levels for a number of areas in which these demographic groups live for the SOCMI and Neoprene Production source categories. See section V.F for an analysis that characterizes populations living in proximity of facilities and risks prior to the final rule.

The EPA believes that this action is likely to reduce existing disproportionate and adverse effects on communities with environmental justice concerns. This action establishes standards for EtO emission sources at HON processes and chloroprene emission sources at neoprene production processes. This action also corrects and clarifies regulatory provisions related to emissions during periods of SSM, including removing general exemptions for periods of SSM and adding work practice standards for periods of SSM where appropriate, addressing flare combustion efficiency, and requiring fenceline monitoring for pollutants that drive cancer risks for HON and neoprene production sources. As a result of these changes, we expect zero people to be exposed to risk levels above 100-in-1 million due to emissions from each of these source categories. See section IV.A of this preamble for more information about the control requirements of the regulation and the resulting reduction in cancer risks.

The EPA additionally identified and addressed environmental justice concerns by engaging in outreach activities to communities we expect to be impacted by chemical plants that emit EtO.

For additional information on potential impacts, see the document titled Analysis of Demographic Factors for Populations Living Near Hazardous Organic NESHAP (HON) Operations—Final; Analysis of Demographic Factors for Populations Living Near Hazardous Organic NESHAP (HON) Operations: Whole Facility Analysis—Final; Analysis of Demographic Factors for Populations Living Near Neoprene Production Operations—Final; Analysis of Demographic Factors for Populations Living Near Neoprene Production Operations: Whole Facility Analysis— Final, which are available in the docket for this rulemaking. Also see the document titled Analysis of Demographic Factors for Populations Living Near Polymers and Resins I and Polymer and Resins II Facilities (Docket Item No. EPA-HQ-OAR-2022-0730-0060).

K. Congressional Review Act (CRA)

This action is subject to the CRA, and the EPA will submit a rule report to each House of the Congress and to the Comptroller General of the United States. This action meets the criteria set forth in 5 U.S.C. 804(2).

List of Subjects

40 CFR Part 60

• Environmental protection
• Administrative practice and procedure
• Air pollution control
• Incorporation by reference
• Intergovernmental relations
• Reporting and recordkeeping requirements

40 CFR Part 63

• Environmental protection
• Air pollution control
• Hazardous substances
• Incorporation by reference
• Intergovernmental relations
• Reporting and recordkeeping requirements

For the reasons set out in the preamble, the Environmental Protection Agency amends title 40, chapter I, part 60 of the Code of Federal Regulations as follows:

PART 60—STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES

1. The authority citation for part 60 continues to read as follows:

Authority: 42 U.S.C. 7401 et seq.

Subpart A—General Provisions

2. Amend § 60.17 by:

a. Revising paragraph (a), paragraphs (c) introductory text, (d) introductory text, and (e) introductory text, and paragraph (g)(14);

b. In paragraph (h):

i. Redesignating paragraphs (h)(221) through (228) as (h)(226) through (233), (h)(196) through (220) as (h)(200) through (224), (h)(171) through (195) as (h)(174) through (198), (h)(115) through (170) as (h)(117) through (172), and (h)(28) through (114) as (h)(29) through (115);

ii. Adding new paragraph (h)(28);

iii. Revising newly redesignated paragraph (h)(78);

iv Adding new paragraphs (h)(116), (173), and (199);

v. Revising newly redesignated paragraphs (h)(217) and (221), and

vi. Adding new paragraph (h)(225); and

c. Revising and republishing paragraph (j); and

d. Removing note 1 to paragraph (k).

The revisions and additions read as follows:

3. Amend § 60.480 by revising paragraph (f) to read as follows:

4. Amend § 60.481 by revising the definition of “Process unit” to read as follows:

5. Amend § 60.482-1 by removing paragraph (g).

6. Amend § 60.485 by revising paragraph (g)(5) to read as follows:

7. Amend § 60.486 by adding paragraph (l) as follows:

8. Amend § 60.487 by revising paragraphs (a) and (f) and adding paragraphs (g), (h), and (i) to read as follows:

9. Revise the heading of subpart VVa to read as follows:

Subpart VVa—Standards of Performance for Equipment Leaks of VOC in the Synthetic Organic Chemicals Manufacturing Industry for Which Construction, Reconstruction, or Modification Commenced After November 7, 2006, and on or Before April 25, 2023

10. Amend § 60.480a by revising paragraphs (b), revising and republishing paragraph (d), and revising paragraph (f) to read as follows:

11. Amend § 60.481a by revising the definitions of “Capital expenditure” and “Process Unit” to read as follows:

12. Amend § 60.482-1a by revising paragraph (e) introductory text and removing paragraph (g).

The revision reads as follows:

13. Remove § 60.482-11a.

14. Amend § 60.485a by revising paragraphs (b) and (g)(5) to read as follows:

15. Amend § 60.486a by:

a. Revising paragraphs (a)(3) introductory text and (b) introductory text;

b. Removing and reserving paragraph (b)(3);

c. Revising paragraphs (c) introductory text and (e) introductory text;

d. Removing and reserving paragraph (e)(9);

e. Revising paragraph (f) introductory text; and

f. Adding paragraph (l).

The revisions and addition read as follows:

16. Amend § 60.487a by:

a. Revising paragraph (a);

b. Removing paragraph (b)(5);

c. Revising paragraph (c)(2)(vi);

d. Removing and reserving paragraphs (c)(2)(vii) and (viii):

e. Revising paragraph (f); and

f. Adding paragraphs (g), (h) and (i).

The revisions and additions read as follows:

17. Add subpart VVb to read as follows:

Subpart VVb—Standards of Performance for Equipment Leaks of VOC in the Synthetic Organic Chemicals Manufacturing Industry for Which Construction, Reconstruction, or Modification Commenced After April 25, 2023

(a)(1) The provisions of this subpart apply to affected facilities in the synthetic organic chemicals manufacturing industry.

(2) The group of all equipment (defined in § 60.481b) within a process unit is an affected facility.

(b) Any affected facility under paragraph (a) of this section that commences construction, reconstruction, or modification after April 25, 2023, shall be subject to the requirements of this subpart.

(c) Addition or replacement of equipment for the purpose of process improvement which is accomplished without a capital expenditure shall not by itself be considered a modification under this subpart.

(d)(1) If an owner or operator applies for one or more of the exemptions in this paragraph, then the owner or operator shall maintain records as required in § 60.486b(i).

(2) Any affected facility that has the design capacity to produce less than 1,000 Mg/yr (1,102 ton/yr) of a chemical listed in § 60.489 is exempt from §§ 60.482-1b through 60.482-11b.

(3) If an affected facility produces heavy liquid chemicals only from heavy liquid feed or raw materials, then it is exempt from §§ 60.482-1b through 60.482-11b.

(4) Any affected facility that produces beverage alcohol is exempt from §§ 60.482-1b through 60.482-11b.

(5) Any affected facility that has no equipment in volatile organic compounds (VOC) service is exempt from §§ 60.482-1b through 60.482-11b.

(e)(1) Option to comply with 40 CFR part 65. (i) Owners or operators may choose to comply with the provisions of 40 CFR part 65, subpart F, to satisfy the requirements of §§ 60.482-1b through 60.487b for an affected facility. When choosing to comply with 40 CFR part 65, subpart F, the requirements of §§ 60.485b(d), (e), and (f), and 60.486b(i) and (j) still apply. Other provisions applying to an owner or operator who chooses to comply with 40 CFR part 65 are provided in 40 CFR 65.1.

(ii) Owners or operators who choose to comply with 40 CFR part 65, subpart F must also comply with §§ 60.1, 60.2, 60.5, 60.6, 60.7(a)(1) and (4), 60.14, 60.15, and 60.16 for that equipment. All sections and paragraphs that are not mentioned in this paragraph (e)(1)(ii) do not apply to owners or operators of equipment subject to this subpart complying with 40 CFR part 65, subpart F, except that provisions required to be met prior to implementing 40 CFR part 65 still apply. Owners and operators who choose to comply with 40 CFR part 65, subpart F, must comply with 40 CFR part 65, subpart A.

(2) Option to comply with 40 CFR part 63, subpart H. (i) Owners or operators may choose to comply with the provisions of 40 CFR part 63, subpart H, to satisfy the requirements of §§ 60.482-1b through 60.487b for an affected facility. When choosing to comply with 40 CFR part 63, subpart H, the requirements of § 60.482-7b, § 60.485b(d), (e), and (f), and § 60.486b(i) and (j) still apply.

(ii) Owners or operators who choose to comply with 40 CFR part 63, subpart H must also comply with §§ 60.1, 60.2, 60.5, 60.6, 60.7(a)(1) and (4), 60.14, 60.15, and 60.16 for that equipment. All sections and paragraphs that are not mentioned in this paragraph (e)(2)(ii) do not apply to owners or operators of equipment subject to this subpart complying with 40 CFR part 63, subpart H, except that provisions required to be met prior to implementing 40 CFR part 63 still apply. Owners and operators who choose to comply with 40 CFR part 63, subpart H, must comply with 40 CFR part 63, subpart A.

(f) Owners and operators of flares that are subject to the flare related requirements of this subpart and flare related requirements of any other regulation in this part or 40 CFR part 61 or 63, may elect to comply with the requirements in § 60.619a, § 60.669a, or § 60.709a, in lieu of all flare related requirements in any other regulation in this part or 40 CFR part 61 or 63.

18. Revise the heading of subpart III to read as follows:

Subpart III—Standards of Performance for Volatile Organic Compound (VOC) Emissions From the Synthetic Organic Chemical Manufacturing Industry (SOCMI) Air Oxidation Unit Processes After October 21, 1983, and on or Before April 25, 2023

19. Amend § 60.610 by revising paragraph (b) introductory text and adding paragraph (e) to read as follows:

20. Amend § 60.611 by revising the definition of “Flame zone” to read as follows:

21. Amend § 60.613 by revising paragraphs (e)(1)(i), (e)(2)(i), and (e)(3)(i) to read as follows:

22. Amend § 60.614 by revising paragraphs (b)(4) introductory text and (e) to read as follows:

23. Amend § 60.615 by revising paragraphs (b) introductory text, (j) introductory text, and (k) and adding paragraphs (m), (n), and (o) to read as follows:

24. Amend § 60.618 by revising paragraph (b) to read as follows:

25. Add subpart IIIa to read as follows:

Subpart IIIa—Standards of Performance for Volatile Organic Compound (VOC) Emissions From the Synthetic Organic Chemical Manufacturing Industry (SOCMI) Air Oxidation Unit Processes for Which Construction, Reconstruction, or Modification Commenced After April 25, 2023

26. Revise the heading of subpart NNN to read as follows:

Subpart NNN—Standards of Performance for Volatile Organic Compound (VOC) Emissions From Synthetic Organic Chemical Manufacturing Industry (SOCMI) Distillation Operations After December 30, 1983, and on or Before April 25, 2023

27. Amend § 60.660 by revising paragraphs (b) introductory text and (c)(6) and adding paragraph (e) to read as follows:

28. Amend § 60.661 by revising the definition of “Flame zone” to read as follows:

29. Amend § 60.664 by revising paragraphs (b)(4) introductory text and (e) to read as follows:

30. Amend § 60.665 by revising paragraphs (b) introductory text, (l) introductory text, (l)(5) and (6), and (m) and adding paragraphs (q), (r), and (s) as follows:

31. Amend § 60.668 by revising paragraph (b) to read as follows:

32. Add subpart NNNa to read as follows:

Subpart NNNa—Standards of Performance for Volatile Organic Compound (VOC) Emissions From Synthetic Organic Chemical Manufacturing Industry (SOCMI) Distillation Operations for Which Construction, Reconstruction, or Modification Commenced After April 25, 2023

Subpart NNNa—Standards of Performance for Volatile Organic Compound (VOC) Emissions From Synthetic Organic Chemical Manufacturing Industry (SOCMI) Distillation Operations for Which Construction, Reconstruction, or Modification Commenced After April 25, 2023

33. Revise the heading for subpart RRR to read as follows:

Subpart RRR—Standards of Performance for Volatile Organic Compound Emissions From Synthetic Organic Chemical Manufacturing Industry (SOCMI) Reactor Processes After June 29, 1990, and on or Before April 25, 2023

34. Amend § 60.700 by revising paragraphs (b) introductory text and (c)(5) and (8) and adding paragraph (e) to read as follows:

35. Amend § 60.701 by revising the definition of “Flame zone” as follows to read as follows:

36. Amend § 60.704 by revising paragraphs (b)(3), (b)(4) introductory text, (d), and (h)(2) and (3) to read as follows:

37. Amend § 60.705 by revising paragraphs (b) introductory text, (l), and (m) and adding paragraphs (u), (v), and (w) to read as follows:

38. Amend § 60.708 by revising paragraph (b) to read as follows:

39. Add subpart RRRa to read as follows:

Subpart RRRa—Standards of Performance for Volatile Organic Compound Emissions From Synthetic Organic Chemical Manufacturing Industry (SOCMI) Reactor Processes for Which Construction, Reconstruction, or Modification Commenced After April 25, 2023