Designation of Areas for Air Quality Planning Purposes; Redesignation Request and Associated Maintenance Plan for Whatcom County, WA 2010 SO2 Nonattainment Area

SUPPLEMENTARY INFORMATION:

Throughout this document, the use of “we” and “our” means the EPA.

I. What is the background for the EPA's proposed actions?

On June 22, 2010, the EPA published a new 1-hour primary SO₂ NAAQS of 75 parts per billion (ppb), which 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 parts per billion (ppb), as determined in accordance with appendix T of 40 CFR part 50 (75 FR 35520). Under Clean Air Act (CAA) section 107(d)(1), the EPA is required to designate areas as “nonattainment,” “attainment,” or “unclassifiable” within two years of establishing a new or revising an existing standard. As part of this process, states must submit recommendations for area designations and boundaries to the EPA within one year of the effective date of the standard. In 2011, Washington State, like many states across the nation, did not have sufficient SO₂ monitoring data for specific stationary sources that may cause or contribute to violations of the revised SO₂ NAAQS and recommended that all areas in the state be designated as unclassifiable. In response to the lack of sufficient SO₂ monitoring data across the nation, the EPA promulgated the Data Requirements Rule (DRR) on August 21, 2015 (80 FR 51052), which established a phased-in approach for state air agencies to characterize air quality via additional monitoring or modeling in areas associated with sources meeting certain criteria. In addition to the original round of nonattainment designations published on August 5, 2013 (78 FR 47191), the EPA promulgated three subsequent rounds of designations in 2016 (81 FR 45039, July 12, 2016), 2018 (83 FR1098, January 9, 2018), and 2021 (86 FR 16055, March 26, 2021), as information to characterize air quality became available. The EPA designated Whatcom County (partial), Washington (also referred to as the “nonattainment area” or “area”) as nonattainment effective April 30, 2021, as part of the Agency's Round 4 designations (86 FR 16055, March 26, 2021).

In the case of Washington, the EPA and the Washington Department of Ecology (Ecology) identified the Alcoa Intalco Aluminum LLC (Intalco) facility, located in the Cherry Point Industrial Area in Whatcom County, as emitting 2,000 tons or more of SO₂ annually, which triggered the DRR requirement for additional modeling or monitoring to characterize air quality in the area. Washington chose to meet this DRR requirement via the establishment of monitoring at the Intalco facility beginning on January 1, 2017. Based on the monitoring data established under the DRR, the Ferndale Mountain View Road monitor (AQS ID 53-073-0017) violated the 75 ppb level of the revised 1-hour primary SO₂ NAAQS with a 2017-2019 design value of 106 ppb. The state did not send an updated formal designation recommendation for Whatcom County. However, Ecology, in collaboration with Northwest Clean Air Agency (NWCAA), submitted a technical report and modeling analysis on June 12, 2020, to help inform the EPA's nonattainment boundary determination using data from the monitors that were installed pursuant to the DRR. Given that the state did not provide a formal recommendation for the boundary, the EPA conducted an extensive review of the submitted modeling to develop sufficient evidence to support the determination of a nonattainment boundary. The nonattainment boundary must contain all of the area where the NAAQS are not attained and all areas that contribute to the violations. Based on our review, the EPA determined that the state's modeling assessment was reliable for determining the extent of the area of violation of the 1-hour primary SO₂ NAAQS. Specifically, we agreed that the region of violation was most likely due to plume downwash at the Intalco facility during certain wind conditions, that the modeled area of violation did not extend far from the Intalco facility fence line, that the gradient of concentration near the areas of violation was steep, quickly dropping with distance from the Intalco facility fence line, and that other nearby industrial facilities did not sufficiently contribute to violations of the 1-hour primary SO₂ NAAQS to warrant inclusion in the NAA boundary. In our final nonattainment boundary determination, we concurred with Ecology and NWCAA's view that the boundary should be drawn to encompass the cause of the SO₂ violations, the Intalco facility. However, we used a simpler nonattainment boundary consisting of four Universal Transverse Mercator (UTM) coordinates instead of the various roadways and property lines suggested by NWCAA in a June 9, 2020, letter. For more information about the specific modeling and the EPA's analysis, please see “Appendix A Whatcom County SO₂ Area Designation” included in the docket for this action.

In response to the EPA's designation of the NAA, Washington submitted an attainment plan on December 15, 2022, to the EPA for approval. This plan and associated order required significant upgrades to the Intalco facility including installation and operation of a new SO₂ wet scrubber. Subsequently, on March 16, 2023, Alcoa Corporation publicly announced their plans to permanently close the Intalco facility. Ecology issued a notice of intent to revoke the associated minor new source review (NSR) and Title V Operating Permits on November 30, 2023, which became effective December 7, 2023. Under Revised Code of Washington (RCW) and Washington Administrative Code (WAC), Intalco cannot operate the facility without first obtaining a new Title V operating permit and applicable NSR permits, including a demonstration of compliance with the 2010 1-hour SO₂ NAAQS. Since the 2022 attainment plan, which imposed specific control requirements on Intalco, became functionally moot with the 2023 permanent closure of the facility, Ecology proceeded directly to submitting a redesignation request and maintenance plan for the area. Upon the EPA's final approval of the redesignation request and maintenance plan for the area, Ecology intends to withdraw the now outdated 2022 attainment plan. The EPA is not proposing to act on the 2022 attainment plan in this action.

II. What are the criteria for redesignation?

The CAA provides the requirements for redesignating a NAA to attainment. Specifically, section 107(d)(3)(E) of the CAA allows for redesignation of a NAA provided that: (1) the Administrator determines that the area has attained the applicable NAAQS; (2) the Administrator has fully approved the applicable implementation plan for the area under section 110(k); (3) the Administrator determines that the improvement in air quality is due to permanent and enforceable reductions in emissions resulting from implementation of the applicable SIP and applicable Federal air pollutant control regulations and other permanent and enforceable reductions; (4) the Administrator has fully approved a maintenance plan for the area as meeting the requirements of section 175A; and (5) the State containing such area has met all requirements applicable to the area for purposes of redesignation under section 110 and part D of the CAA.

On April 16, 1992, the EPA provided guidance on redesignation in the General Preamble for the Implementation of title I of the CAA Amendments of 1990 (57 FR 13498) and supplemented this guidance on April 28, 1992 (57 FR 18070). The EPA has provided further guidance on processing redesignation requests in several guidance documents. For the purposes of this action, the EPA will be referencing two of these documents: (1) the September 4, 1992, Memorandum from John Calcagni titled “Procedures for Processing Requests to Redesignate Areas to Attainment,” (hereafter referred to as the “Calcagni Memo”); and (2) the April 23, 2014, Memorandum from Stephen D. Page titled “Guidance for 1-Hour SO₂ Nonattainment Area SIP Submissions,” (hereafter referred to as “2014 SO₂ NAA Guidance”).

III. What is the EPA's analysis of the request?

The EPA's evaluation of Washington's redesignation request and maintenance plan was based on consideration of the five redesignation criteria provided under CAA section 107(d)(3)(E).

Criteria (1)—The Whatcom County (Partial) SO ₂ Nonattainment Area Has Attained the 2010 1-Hour SO ₂ NAAQS

For redesignating a NAA, the CAA requires the EPA to determine that the area has attained the applicable NAAQS (CAA section 107(d)(3)(E)(i)). The two primary methods for evaluating ambient air quality impacted by SO₂ emissions are through dispersion modeling and air quality monitoring. For SO₂, an area may be considered attaining the 2010 1-hour SO₂ NAAQS if it meets the NAAQS as determined in accordance with 40 CFR 50.17 and appendix T of part 50, based on three complete, consecutive calendar years of quality-assured air quality monitoring data. To attain the NAAQS based on monitoring, the 3-year average of the annual 99th percentile (fourth highest value) of 1-hour daily maximum concentrations measured at each monitor within an area must be less than or equal to 75 ppb. The data must be collected and quality-assured in accordance with 40 CFR part 58 and recorded in the EPA Air Quality System (AQS). The EPA's determination of attainment can be based on monitoring data alone, without the need for dispersion modeling analyses, if the air agency provides an analysis demonstrating that the monitor(s) for the affected area is located in the area of maximum ambient concentration of SO₂ .

In this action, the EPA is proposing to determine that the Whatcom County (partial) SO₂ nonattainment area is attaining the 2010 1-hour SO₂ NAAQS. The EPA reviewed SO₂ monitoring data from the two monitoring stations inside the Whatcom County (partial) SO₂ nonattainment area, the Ferndale-Mountain View Road station (AQS Site ID 53-073-0017) and the Ferndale-Kickerville Road station (AQS Site ID 53-073-0013). The monitoring station data have been quality-assured, are recorded in the EPA's Air Quality System (AQS), and indicate that the area is attaining the 2010 1-hour SO₂ NAAQS. The fourth-highest 1-hour SO₂ values at the monitoring stations for the 3-year averages of these values ( i.e., design values), are summarized in Table 1, below.