Utah; Northern Wasatch Front; 2015 8-Hour Ozone Nonattainment Area Boundary Expansion and Applicability of Certain Clean Air Act Requirements

ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 81</CFR> <DEPDOC>[EPA-R08-OAR-2025-0001; FRL-12971-01-R8]</DEPDOC> <SUBJECT>Utah; Northern Wasatch Front; 2015 8-Hour Ozone Nonattainment Area Boundary Expansion and Applicability of Certain Clean Air Act Requirements</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Environmental Protection Agency (EPA). <HD SOURCE="HED">ACTION:</HD> Proposed rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The Environmental Protection Agency (EPA) is proposing to approve a request to expand the boundary for the Northern Wasatch Front (NWF) 2015 8-hour ozone national ambient air quality standard (NAAQS) nonattainment area (NAA). The request was submitted by the State of Utah on February 27, 2023. The newly expanded portion of the NWF NAA will have the same classification as the original NWF NAA under the 2015 ozone NAAQS and all applicable Clean Air Act (CAA) requirements will become applicable to the newly designated portion upon the effective date of the final action. The EPA is taking this action pursuant to the CAA. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Written comments must be received on or before October 27, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> Submit your comments, identified by Docket ID No. EPA-R08-OAR-2025-0001, to the Federal Rulemaking Portal: <E T="03">https://www.regulations.gov</E> . Follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from <E T="03">https://www.regulations.gov</E> . The EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission ( <E T="03">i.e.,</E> on the web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit <E T="03">https://www.epa.gov/dockets/commenting-epa-dockets</E> . <E T="03">Docket:</E> All documents in the docket are listed in the <E T="03">https://www.regulations.gov</E> index. Although listed in the index, some information is not publicly available, <E T="03">e.g.,</E> CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available electronically in <E T="03">https://www.regulations.gov</E> . Please email or call the person listed in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section if you need to make alternative arrangements for access to the docket. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Amanda Brimmer, Air and Radiation Division, EPA, Region 8, Mailcode 8ARD-AQ-R, 1595 Wynkoop Street, Denver, Colorado 80202-1129, telephone number: (303) 312-6323, email address: <E T="03">brimmer.amanda@epa.gov</E> . </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> Throughout this document wherever “we,” “us,” or “our” is used, we mean the EPA. <HD SOURCE="HD1">I. Background</HD> On October 26, 2015, the EPA revised the national standards for ground-level ozone, promulgating identical primary and secondary ozone standards that specified an 8-hour ozone level of 0.070 parts per million (ppm). <SU>1</SU> <FTREF/> In a separate action, the EPA assigned classification thresholds and attainment dates based on each NAA's monitored ozone levels. <SU>2</SU> <FTREF/> Consistent with CAA section 181(a), the EPA established attainment dates based on nonattainment classification; with the attainment date for Marginal areas as August 3, 2021 and Moderate areas as August 3, 2024. <FTNT> <SU>1</SU>  National Ambient Air Quality Standards for Ozone, 80 FR 65452 (Oct. 26, 2015). </FTNT> <FTNT> <SU>2</SU>   <E T="03">See</E> 83 FR 10376 (May 8, 2018). </FTNT> Upon promulgation of the revised 2015 ozone NAAQS, the State of Utah submitted initial designations to the EPA based on monitored air quality data from 2013-2015 and recommended that Salt Lake and Davis Counties, and portions of Weber and Tooele Counties be designated as nonattainment. The EPA did not modify the State's initial designation and, effective August 3, 2018, the EPA designated the NWF as a Marginal NAA. <SU>3</SU> <FTREF/> <FTNT> <SU>3</SU>   <E T="03">See</E> 83 FR 25776 (Jun. 4, 2018), including Docket ID No.`EPA-HQ-OAR-2017-0548-0148', titled, “EPA's preliminary response to Utah's recommendations and information about EPA's approach for completing designations for the revised ozone standards”. </FTNT> On October 7, 2022, the EPA determined that the NWF did not attain the NAAQS by the Marginal attainment date, and the area was subsequently reclassified by operation of law to a Moderate NAA. <SU>4</SU> <FTREF/> A State Implementation Plan (SIP) outlines how states will implement controls to satisfy statutory and regulatory requirements under the 2015 ozone NAAQS and demonstrate how the area will attain the ozone standard by the attainment date. The submission deadline for a majority of the required ozone SIP elements was established as January 1, 2023 for Moderate ozone NAA's. The EPA's implementing regulations at 40 Code of Federal Regulations (CFR) 51.1308-51.1315 address ozone SIP requirements including attainment demonstrations, Reasonable Further Progress (RFP) and associated milestone demonstrations, reasonably available control technology (RACT), reasonably available control measures (RACM), major nonattainment new source review, emission inventories, the timing of required SIP submissions, and compliance with emission control measures in the SIP. <FTNT> <SU>4</SU>   <E T="03">See</E> 87 FR 60897 (Oct. 7, 2022). </FTNT> In 2020 and 2021, the State of Utah submitted Marginal SIP elements to the EPA, which were approved in 2021 and 2022 respectively. <SU>5</SU> <FTREF/> On December 12, 2024, Utah submitted a Moderate ozone SIP to meet CAA section 182(b) and which was deemed complete by operation of law on June 12, 2025. <SU>6</SU> <FTREF/> The EPA is currently reviewing the submitted Moderate SIP elements and will be acting on them in future actions. <FTNT> <SU>5</SU>   <E T="03">See</E> 86 FR 35405 (Jul. 6, 2021) and 87 FR 24275 (Apr. 25, 2022). </FTNT> <FTNT> <SU>6</SU>  40 CFR part 51, appendix V, section 1.1.2. </FTNT> In December 2024, the NWF NAA was reclassified to Serious by operation of law due to an EPA finding of failure to attain by the Moderate attainment date. That action reclassified the area to Serious by operation of law with an effective date of January 8, 2025. <SU>7</SU> <FTREF/> However, the Final Rule was stayed by the 10th Circuit Court of Appeals in April 2025 due to petitions for review that were filed by the State of Utah and the Utah Petroleum Association (UPA) and the EPA is currently in the process of reconsidering the final action. <SU>8</SU> <FTREF/> The practical implication of this judicial stay is that the NWF NAA is currently classified as Moderate as of the date of this proposal. The stay will be lifted pending EPA concluding its reconsideration. In the event the classification of Serious is retained, the NWF would again be subject to Serious Area planning requirements consistent with CAA section 182(c). The classification and applicable requirements for the current NAA will also apply to the newly redesignated area, if this proposal is finalized. <FTNT> <SU>7</SU>   <E T="03">See</E> 89 FR 97545 (Dec. 9, 2024). </FTNT> <FTNT> <SU>8</SU>   <E T="03">See State of Utah and UPA</E> v. <E T="03">U.S. Environmental Protection Agency</E> , No. 25-9519 (10th Cir. 2025). </FTNT> <HD SOURCE="HD1">II. Utah's Submittal</HD> The State's modeling efforts associated with the Moderate SIP development for the 2015 ozone NAAQS showed that large amounts of nitrogen oxides (NO <E T="52">X</E> ) and volatile organic compound (VOC) emissions from a source located upwind of the NAA, namely US Magnesium LLC (US Magnesium), was directly impacting high ozone levels within the NWF NAA. Located in Tooele County on the southwestern edge of the Great Salt Lake, US Magnesium has significant amounts of precursor emissions that contribute to both ozone and fine particulate matter (PM <E T="52">2.5</E> ) formation along the Wasatch Front in addition to also producing halogen emissions which further increase ozone formation. <SU>9</SU> <FTREF/> <FTNT> <SU>9</SU>   <E T="03">See</E> UDAQ, Supporting Documentation, Request for Adjustment of the Northern Wasatch Front Nonattainment Area Boundary for the 2015 8-hour Ozone National Ambient Air Quality Standard, Feb. 27, 2023. </FTNT> On February 27, 2023, the State of Utah submitted a request to the EPA to expand the NAA boundary of the NWF to include the US Magnesium facility. <SU>10</SU> <FTREF/> US Magnesium was initially omitted from the NWF NAA based on the State's recommendation that the ozone nonattainment boundary be identical to the 2006 24-hour PM <E T="52">2.5</E> nonattainment boundary for Davis, Salt Lake, Tooele, and Weber Counties. <SU>11</SU> <FTREF/> This recommendation was based on assessing the impact of emissions during the winter months since that is when the Salt Lake City region tends to experience PM <E T="52">2.5</E> exceedances. 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