Finding of Failure To Attain the Primary 2010 1-Hour Sulfur Dioxide Standard for the San Juan and Guayama-Salinas Nonattainment Areas; Approval and Conditional Approval of Air Quality State Implementation Plans; Puerto Rico; Attainment Plan for the 2010 1-Hour Sulfur Dioxide Standard for the San Juan and Guayama-Salinas Nonattainment Areas

SUPPLEMENTARY INFORMATION:

Public Information Session

The EPA intends to provide two public information sessions concerning this proposed rule. The EPA will announce the date, time, and location for each session on its website. These public information sessions will provide informal opportunities for members of the public to learn about this proposed action. The EPA anticipates these sessions will allow the public to be better informed when submitting formal comments during the 60-day comment period for this proposed action.

A translator will be present at the public engagement sessions to ensure participants are able to understand the information provided by the EPA. There will be no recording or transcript of these public information sessions since these sessions are not considered to be formal public hearings. Statements made and/or questions asked at these sessions will not be considered formal comments on the proposed rule and will not be included in the EPA's response to comments, unless submitted as a formal comment on the record.

Members of the public who wish to formally comment should do so during the 60-day public comment period provided following the publication of this proposed rule.

This notice is organized as follows:

Table of Contents

I. Background

A. The 2010 SO₂ NAAQS

B. Designations and Attainment Date Requirements for the 2010 SO₂ NAAQS

C. Finding of Failure To Submit and SIP Submittal

D. Puerto Rico's Integrated Resource Plan

II. What is the EPA proposing?

III. Proposed Determination of Failure To Attain and the Associated Consequences

A. Applicable Statutory and Regulatory Provisions

B. San Juan and Guayama-Salinas SO₂ Monitoring Networks and Considerations

C. SO₂ Data Considerations and the EPA's Proposed Determination

1. SO₂ Monitor Data

2. Modeling Data and Control Strategy Timeline

3. Failure To Implement the Control Strategy

4. SO₂ Emissions Data

5. Weight-of-Evidence Analysis Conclusions and the EPA's Proposed Determination

D. Consequences for SO₂ NAAs Failing To Attain Standards by Attainment Dates

IV. Requirements for SO₂ Nonattainment Area Plans

V. Review of Modeled Attainment Demonstration

A. Modeling Approach

B. Area of Analysis

C. Receptor Grid

D. Meteorological Data

E. Source Characterization

F. Emissions Data

G. Retirements and Emission Limits

H. Background Concentrations

I. Summary of Results

VI. Review of Other Plan Requirements

A. Emissions Inventory

B. RACM and RACT and Enforceable Emission Limitations and Control Measures

C. New Source Review

D. Reasonable Further Progress

E. Contingency Measures

F. Conformity

VII. Puerto Rico's New Source Review Program

VIII. The EPA's Evaluation of Rule 425

IX. Environmental Justice Considerations

X. The EPA's Proposed Action

XI. Incorporation by Reference

XII. Statutory and Executive Order Reviews

I. Background

A. The 2010 SO ₂ NAAQS

Under section 109 of the Clean Air Act (CAA), the EPA has established primary and secondary NAAQS for certain pervasive air pollutants (referred to as “criteria pollutants”) and conducts periodic reviews of the NAAQS to determine whether they should be revised or whether new NAAQS should be established. The primary NAAQS represent ambient air quality standards the attainment and maintenance of which the EPA has determined, including a margin of safety, are requisite to protect the public health. The secondary NAAQS represent ambient air quality standards the attainment and maintenance of which the EPA has determined are requisite to protect the public welfare from any known or anticipated adverse effects associated with the presence of such air pollutant in the ambient air.

Under the CAA, the EPA must establish NAAQS for criteria pollutants, including SO₂ . SO₂ is primarily released to the atmosphere through the burning of fossil fuels by power plants and other industrial facilities. Short-term exposure to SO₂ can damage the human respiratory system and increase breathing difficulties. Small children and people with respiratory conditions, such as asthma, are more sensitive to the effects of SO₂. Sulfur oxides at high concentrations in ambient air can also react with compounds to form small particulates that can penetrate deeply into the lungs and cause health problems.

The EPA first established primary SO₂ standards in 1971 at 0.14 parts per million (ppm) over a 24-hour averaging period and 0.3 ppm over an annual averaging period. On June 22, 2010, the EPA revised the primary NAAQS for SO₂ and published a new 1-hour primary SO₂ NAAQS of 75 parts per billion (ppb). The intent of this revision is to provide increased protection of public health, providing for revocation of the 1971 primary annual and 24-hour SO₂ standards for most areas of the country following area designations under the new NAAQS.

The 2010 standard is met at an ambient air quality monitoring site when the 3-year average of the annual 99th percentile of daily maximum 1-hour average concentrations does not exceed 75 ppb, or 0.075 ppm, as determined in accordance with Appendix T of 40 CFR part 50.17. The EPA established the SO₂ NAAQS based on significant evidence and numerous studies demonstrating that serious health effects are associated with short-term exposures to SO₂ emissions ranging from five minutes to 24 hours, including an array of adverse respiratory effects such as narrowing of the airways, which can cause difficulty breathing (bronchoconstriction) and increased asthma symptoms. For more information regarding the health impacts of SO_2, please refer to the June 22, 2010 final rulemaking. See75 FR 35520, codified at 40 CFR 50.17.

B. Designations and Attainment Date Requirements for the 2010 SO ₂ NAAQS

Following promulgation of a new or revised NAAQS, the EPA is required by the CAA to designate areas throughout the United States as attaining or not attaining the NAAQS; this designation process is described in section 107(d)(1)-(2) of the CAA. For the 2010 SO₂ NAAQS, the EPA defined a nonattainment area (NAA) as an area that the EPA determined violates the 2010 1-hour primary SO₂ NAAQS and/or contributes to a violation in a nearby area, based on the most recent 3 years of air quality monitoring data, appropriate dispersion modeling analysis, and any other relevant information.

On January 9, 2018, the EPA, as part of the third round of area designations for the 2010 1-hour primary SO₂ NAAQS, designated six areas of the country as nonattainment, including the San Juan and Guayama-Salinas NAAs. These area designations had an effective date of April 9, 2018.

Areas designated nonattainment for the SO₂ NAAQS are subject to the general NAA planning requirements of CAA section 172 and to the SO₂ -specific planning requirements of subpart 5 of part D of Title I of the CAA (sections 191 and 192). All components of the SO₂ part D nonattainment area SIP, including the emissions inventory, attainment demonstration, reasonably available control measures (RACM) and reasonably available control technology (RACT), enforceable emissions limitations and control measures, Reasonable Further Progress (RFP) plan, nonattainment New Source Review (NNSR) program, and contingency measures, are due to the EPA within 18 months of the effective date of designation of a nonattainment area under CAA section 191.

Therefore, the nonattainment area SIPs for areas designated effective April 9, 2018, were due on October 9, 2019. These SIPs are required to demonstrate that their respective areas will attain the 2010 1-hour primary SO₂ NAAQS as expeditiously as practicable, but no later than five years from the effective date of designation, or by April 9, 2023, for the San Juan and Guayama-Salinas NAAs.

C. Finding of Failure To Submit and SIP Submittal

For a number of SO₂ NAAs, including the San Juan and Guayama-Salinas NAAs, the EPA published an action on November 3, 2020, effective December 3, 2020, finding that Puerto Rico and other pertinent states had failed to submit the required SO₂ nonattainment plan by the submittal deadline. See85 FR 69504. This finding initiated a deadline under CAA section 179(a) for the potential imposition of two sanctions clocks related to new source review offsets ( i.e., “2-to-1 offsets”) and highway funding, within 18 and 24 months of the findings, respectively, unless the states and territories subject to the finding made the necessary complete SIP submittal. Additionally, this finding initiated a deadline under CAA section 110(c) for the EPA to promulgate a Federal Implementation Plan (FIP) within two years of the finding unless, by that time, the EPA had approved the submittal as meeting applicable requirements.

On June 3, 2022, the 2-to-1 offset sanctions took effect within the Puerto Rico NAAs. Before the highway funding sanctions could go into effect within the NAAs on December 3, 2022, the Puerto Rico Department of Natural and Environmental Resources (PRDNER) submitted a nonattainment plan for the San Juan and Guayama-Salinas NAAs ( i.e., San Juan and Guayama-Salinas SO₂ plan) on November 22, 2022, and the EPA deemed the PRDNER's submittal administratively and technically complete on December 2, 2022. As a result of the EPA's determination, the 2-to-1 offset sanctions clock was stopped and the highway sanctions never took effect, per the EPA's sanctions regulations at 40 CFR 52.31; however, this completeness determination did not terminate the EPA's FIP obligation that was triggered by the EPA's November 3, 2020, Finding of Failure to Submit.

Within the San Juan and Guayama-Salinas SO₂ plan, amendments to Puerto Rico's RCAP were submitted for the EPA's approval. The RCAP amendments incorporate the SO₂ control measures and nonattainment provisions of the SO₂ plan and would become federally enforceable upon final approval by the EPA. The RCAP amendments consist of revisions to Rule 102, “Definitions,” as well as the adoption of Rule 210, “Non-Attainment Provisions,” and Rule 425, “Provisions for SO₂ Non-Attainment Areas.” The PRDNER's permitting requirements to construct new sources or modify major sources of emissions of SO₂ and other pollutants in NAAs, including the San Juan and Guayama-Salinas NAAs, are set forth in the revisions to Rule 102, “Definitions,” and the recently adopted Rule 210, “Nonattainment Provisions.” Finally, the recently promulgated Rule 425 was adopted to include control measures, emission limits, test methods and procedures, reporting and recordkeeping requirements, and contingency measures for the San Juan and Guayama-Salinas NAAs.

D. Puerto Rico's Integrated Resource Plan

The compliance strategy for Puerto Rico's SIP, and the accompanying RCAP amendments, were developed based on the most recent Integrated Resource Plan (IRP) approved by the Puerto Rico Energy Bureau (PREB), as well as additional updates provided by the PREB, which considered emission unit retirements within the San Juan and Guayama-Salinas NAAs following the integration of renewable energy sources.

The IRP is a plan that is required under Puerto Rico law, with the purpose of providing cost-effective electrical power to meet Puerto Rico's energy demand over a twenty-year planning period, while considering energy conservation, resiliency, reliability, efficiency, transparency, and the environment. Under Act 57-2014, a Puerto Rico law known as the Puerto Rico Energy Transformation and RELIEF Act, the Puerto Rico Electric Power Authority (PREPA), or the electric utility responsible for the operation of the electric power transmission and distribution system (currently LUMA Energy), is required to prepare an IRP for the PREB's approval, which considers reasonable resources to satisfy energy demand for up to a twenty-year period. Puerto Rico's electric utility is also responsible for updating the plan at least every three years to reflect changes in energy market conditions, regulations, fuel prices, and capital costs. Pursuant to Act 57-2014, the PREB is responsible for establishing and implementing regulations to ensure the capacity, reliability, safety, and efficiency of Puerto Rico's electrical system. This includes evaluating and approving the IRP, overseeing and ensuring compliance, and implementation.

On August 24, 2020, the PREB issued the IRP Final Order, based on the IRP submitted by PREPA. The Approved IRP included a Modified Preferred Resource Plan (Action Plan) considering specific power generation capacity additions and retirements. In the Approved IRP, the PREB established a schedule for minimum quantities of renewable resources, and battery energy storage resources to be procured through the Requests for Proposals processes, to be completed by June 2023. The Approved IRP also directed PREPA to submit a renewable resource and battery energy storage procurement plan. Specifically, the Approved IRP included a program for six tranches of procurement for renewable energy and battery storage resources that would add 3,750 MW of renewable sources to the energy grid. Based on the procurement of renewable resources to be integrated in the Puerto Rico Electric System, the Approved IRP authorized the retirement of PREPA's older, oil-fired steam resources, combined cycle turbines and peaking units for the period between 2021 and 2025.

The PREB provided an updated schedule for emission unit retirements and the integration of new renewable energy and battery storage resources via letter to the PRDNER on October 18, 2022, which was updated on November 15, 2022. The IRP was scheduled to be revised and submitted to the PREB by June 28, 2024 by LUMA, the current operator of Puerto Rico's electrical power transmission and distribution system. However, on June 7, 2024, LUMA requested that the PREB suspend the June 28 deadline, due to modeling delays associated with its base case scenario. LUMA requested that the 2024 IRP be filed on May 16, 2025, with an analysis of four supplemental scenarios proposed to be filed on June 19, 2025. On August 20, 2024, the PREB denied LUMA's request for an extension, until May 16, 2025, for a full IRP.

The PREB ordered LUMA to file the Preferred Resource Plan and “salient components” of the base case and alternative case scenarios by no later than November 29, 2024, and ordered LUMA to file certain transmission and distribution related requirements by no later than February 28, 2025.

II. What is the EPA proposing?

The EPA is proposing several actions in this rulemaking. First, under CAA section 179(c), the EPA is proposing to determine that the San Juan and Guayama-Salinas SO₂ NAAs failed to attain the 2010 1-hour primary SO₂ standard by the statutory attainment date of April 9, 2023. The EPA's proposed Finding of Failure to Attain (FFA) determination is based on a weight-of-evidence analysis that demonstrates that the San Juan and Guayama-Salinas areas failed to attain the standard by the mandatory attainment date. The EPA's reasoning for this decision is described in Section III of the preamble.

Second, the EPA is proposing to approve certain elements of Puerto Rico's SO₂ plan, which was submitted to demonstrate how the San Juan and Guayama-Salinas areas would meet the 2010 1-hour SO₂ standard in the San Juan and Guayama-Salinas NAAs. The EPA outlines the requirements for nonattainment plans under CAA section 172(c), and reviews Puerto Rico's plan against these requirements in Sections IV, V and VI of this preamble.

Although Puerto Rico submitted its plan to satisfy CAA section 172(c) requirements, the EPA is proposing to approve only specific elements at this time for compliance with the CAA. The elements being proposed for approval include Puerto Rico's NNSR program and base year emissions inventory. The EPA is not proposing action on other elements of the plan, such as the attainment demonstration, RFP, RACM/RACT, emission limitation as necessary to provide for NAAQS attainment, and contingency measures. The EPA will address whether Puerto Rico is meeting its statutory obligations for those elements in a future rulemaking. Finally, amendments to the RCAP, which Puerto Rico submitted with the plan, are being proposed for approval, in part, and conditional approval, in part, based on providing SIP-strengthening.

III. Proposed Determination of Failure To Attain and the Associated Consequences

A. Applicable Statutory and Regulatory Provisions

Section 179(c)(1) of the CAA requires the EPA to determine whether a NAA attained an applicable standard by the applicable attainment date based on the area's air quality as of the attainment date. In determining the attainment status of SO₂ NAAs, the EPA may consider ambient monitoring data, air quality dispersion modeling, and/or a demonstration that the control strategy in the SIP has been fully implemented.

Under the EPA's regulations in 40 CFR 50.17, and in accordance with 40 CFR part 50 Appendix T, the 2010 1-hour annual SO₂ standard is met when the design value is less than or equal to 75 ppb. Design values are calculated by computing the three-year average of the annual 99th percentile daily maximum 1-hour average concentrations. An SO₂ 1-hour primary standard design value is valid if it encompasses three consecutive calendar years of complete data. A year is considered complete when all four quarters are complete, and a quarter is complete when at least 75 percent of the sampling days are complete. A sampling day is considered complete if 75 percent of the hourly concentration values are reported; this includes data affected by exceptional events that have been approved for exclusion by the Administrator.

A determination of whether an area's air quality meets applicable standards is generally based upon the most recent three calendar years of complete, quality-assured data gathered at established state and local air monitoring stations (SLAMS) in a nonattainment area and entered into the EPA's Air Quality System (AQS) database. Data from ambient air monitors operated by state and local agencies in compliance with the EPA monitoring requirements must be submitted to AQS. Monitoring agencies annually certify that these data are accurate to the best of their knowledge. All certified SO₂ air monitoring data are used to calculate design values that are used to determine the area's air quality status in accordance with 40 CFR part 50, Appendix T.

In addition to utilizing ambient monitoring data to make determinations of attainment by the attainment date, the EPA considers air quality dispersion modeling and/or a demonstration that the control strategy in the SIP has been fully implemented. With regard to the use of monitoring data for such determinations, EPA's 2014 Nonattainment SO₂ Guidance specifically notes that if the EPA determines the air quality monitors located in the affected area are located in the area of maximum concentration, the EPA may be able to use the data from these monitors to make the determination of attainment without the use of air quality modeling data. In this case, there are SO₂ monitors within the San Juan and Guayama-Salinas NAAs; however, there is no evidence indicating that the monitors are located within the areas of expected maximum concentration.

Due to insufficient monitoring data collected for all three years in the 2020-2022 data period for the SO₂ monitors, the EPA is unable to determine valid monitor-based 2020-2022 design values. As a result, the EPA has considered available air modeling data submitted by the PRDNER with its November 22, 2022, SIP revision, as well as the designation modeling the EPA used to initially determine that the areas were in nonattainment, to assess whether the areas attained by the attainment date.

According to the EPA's Modeling Technical Assistance Document (TAD), for the purpose of modeling to characterize air quality for use in designations, the recommended approach is to use the most recent 3 years of actual emissions data and concurrent meteorological data. However, the TAD also indicates that it would be acceptable to use allowable emissions in the form of the most recently permitted (referred to as PTE or allowable) emissions rate that is federally enforceable and effective. When relying on a modeling demonstration based on allowable emissions for purposes of determining attainment by the attainment date, the EPA looks to whether the emission limit or limits were adopted and whether the relevant source or sources were complying with those modeled limits prior to the attainment date. That is, when determining attainment by the attainment date using air quality modeling of allowable emissions, the EPA looks to whether the state/commonwealth has demonstrated that the control strategy in the SIP has been fully implemented. This is necessary because a modeling demonstration based on allowable emissions is not itself sufficient since, without the supporting emissions information reflected in the control strategy, there would be no way to confirm that the actual emissions were below the modeled limits within the period under review.

The EPA would like to clarify that a significant amount of information is required for the EPA to accurately conduct its own air quality dispersion modeling to determine attainment by the attainment date for these two NAAs. This information is not readily available, and the limited data currently accessible to the Agency raises concerns about the reliability of new modeling. Specifically, the EPA does not have access to fuel use data or concurrent meteorological data and continuous emissions monitoring systems (CEMS) data from the stacks at the PREPA facilities (the EPA also believes that CEMS provide acceptable historical emissions information). As a result, it is the EPA's position that any air quality dispersion modeling the EPA would perform for the purpose of this determination would not be representative of air quality within the areas. Thus, the EPA is not performing air quality dispersion modeling to support its determination that the areas have failed to attain by their attainment dates. The EPA will instead consider the modeling conducted and provided by the PRDNER in its November 22, 2022, SIP submission, which shows that controls that PRDNER anticipates will lead to attainment were not in place prior to the areas' attainment dates.

As noted earlier in this section, the EPA may also consider whether the state (or commonwealth) has demonstrated that the control strategy in the SIP has been fully implemented. That said, the PRDNER's control strategy has not been implemented, nor has it been approved by the EPA. As a result, the EPA cannot determine that the subject sources have achieved compliance with either the PRDNER's control strategy as submitted to the EPA, or a SIP-approved strategy. To address this, the EPA is proposing a determination that the areas did not attain by their attainment date which is based on a technical analysis of various evidence available ( i.e., weight-of-evidence analysis): including the control strategy timeline Puerto Rico identified and adopted into its RCAP, which was determined in coordination with the air quality dispersion modeling submitted within its November 22, 2022 SIP revision as well as the EPA's designation modeling; Puerto Rico's failure to implement the control strategy in a timely manner thus far; and the EPA's review of annual facility-wide emissions data from January 2020 through December 2022 for the PREPA San Juan, PREPA Palo Seco, and PREPA Aguirre facilities located within the NAAs—as described in Sections III.B and III.C of this notice. As noted, the determination of whether the monitors are located in the area of maximum concentration is not needed here, because a demonstration is not being made that the NAAs have attained the 2010 SO₂ NAAQS by the April 9, 2023 attainment date.

B. San Juan and Guayama-Salinas SO ₂ Monitoring Networks and Considerations

Section 110(a)(2)(B)(i) of the CAA requires states to establish and operate air monitoring networks to compile data on ambient air quality for all criteria pollutants. The EPA's monitoring requirements are specified by regulation in 40 CFR part 58. These requirements are applicable to state, and where delegated, local air monitoring agencies that operate criteria pollutant monitors. The regulations in 40 CFR part 58 establish specific requirements for operating air quality surveillance networks to measure ambient concentrations of SO₂, including requirements for measurement methods, network design, quality assurance procedures, and the minimum number of monitoring sites designated as SLAMS.

In sections 4.4 and 4.5 of Appendix D to 40 CFR part 58, the EPA specifies the minimum requirements for SO₂ monitoring sites to be classified as SLAMS. SLAMS produce data that are eligible for comparison with the NAAQS, and therefore, the monitor must be an approved federal reference method (FRM), federal equivalent method (FEM), or approved regional method (ARM) monitor, pursuant to section 2 of Appendix C to 40 CFR part 58. Additionally, Appendix A to 40 CFR part 58 specifies quality assurance requirements for SLAMS monitors.

During the 2020-2022 data period, the PRDNER operated three SO₂ SLAMS in the San Juan and Guayama-Salinas SO₂ NAAs. In the San Juan NAA, SLAMS monitors are in operation at Bayamón (AQS Site ID 72-021-0010, Avenue Central Correcional) and at Cataño (AQS Site ID 72-033-0004, Northwest Street at the 11 Final Street, Las Vegas). In the Guayama-Salinas NAA, a SLAMS monitor is located at Guayama (AQS Site ID 72-057-0011, Road #3 Cuartel Vehiculos Hurtados).

C. SO ₂ Data Considerations and the EPA's Proposed Determination

1. SO₂ Monitor Data

As discussed in Section I.B of this preamble, the applicable attainment date for the San Juan and Guayama-Salinas areas was April 9, 2023. In accordance with Appendix T to 40 CFR part 50, determinations of SO₂ NAAQS compliance are based on three consecutive calendar years of data. To determine the air quality as of the attainment date in the nonattainment area, the EPA reviewed the available data collected during the three calendar years immediately preceding the attainment date for the San Juan and Guayama-Salinas areas ( i.e., January 1, 2020 through December 31, 2022), as well as SO₂ emissions data that resulted from the burning of fossil fuels for electricity generation at the PREPA San Juan, PREPA Palo Seco, and PREPA Aguirre facilities.

The available annual 99th percentile daily maximum 1-hour average SO₂ data at each monitoring site within the San Juan and Guayama-Salinas areas for the 2020-2022 period are presented in Tables 1 and 2 below. Moreover, the 1-hour SO₂ design values at the Bayamón, Cataño, and Guayama SO₂ monitoring sites for the 2020-2022 period are shown in Tables 1 and 2 below.