Approval of Air Quality Implementation Plans; Arizona; Arizona Department of Environmental Quality; Stationary Source Permits; West Pinal County; PM10

<RULE> ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 52</CFR> <DEPDOC>[EPA-R09-OAR-2025-1113; FRL-12927-02-R9]</DEPDOC> <SUBJECT> Approval of Air Quality Implementation Plans; Arizona; Arizona Department of Environmental Quality; Stationary Source Permits; West Pinal County; PM <E T="0735">10</E> </SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Environmental Protection Agency (EPA). <HD SOURCE="HED">ACTION:</HD> Final action. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The Environmental Protection Agency (EPA) is taking final action to fully approve the Arizona Department of Environmental Quality's (ADEQ or “State”) portion of the Arizona State Implementation Plan (SIP) under the Clean Air Act (CAA or “the Act”) that addresses Nonattainment New Source Review (NNSR) permitting for precursor emissions from major stationary sources for purposes of the 1987 PM <E T="52">10</E> National Ambient Air Quality Standards (NAAQS or standard) in the West Pinal PM <E T="52">10</E> nonattainment area. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> This action is effective January 12, 2026. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> The EPA has established a docket for this action under Docket ID No. EPA-R09-OAR-2025-1113. All documents in the docket are listed on the <E T="03">https://www.regulations.gov</E> website. Although listed in the index, some information is not publicly available, <E T="03">e.g.,</E> 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 through <E T="03">https://www.regulations.gov,</E> or please contact the person identified in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section for additional availability information. If you need assistance in a language other than English or if you are a person with a disability who needs a reasonable accommodation at no cost to you, please contact the person identified in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Rebecca Newhouse, EPA Region IX, 75 Hawthorne St., San Francisco, CA 94105; telephone number: (415) 972-3936; email address: <E T="03">newhouse.rebecca@epa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> Throughout this document, “we,” “us” and “our” refer to the EPA. <HD SOURCE="HD1">Table of Contents </HD> <EXTRACT> <FP SOURCE="FP-2">I. Proposed Action</FP> <FP SOURCE="FP-2">II. Public Comment and EPA Response</FP> <FP SOURCE="FP-2">III. EPA Action</FP> <FP SOURCE="FP-2">IV. Statutory and Executive Order Reviews</FP> </EXTRACT> <HD SOURCE="HD1">I. Proposed Action</HD> On September 11, 2025 (90 FR 43980), the EPA proposed to fully approve ADEQ's NNSR permitting program for precursor emissions from major stationary sources for the 1987 PM <E T="52">10</E> NAAQS in the West Pinal PM <E T="52">10</E> nonattainment area because we determined that it fulfills the relevant CAA requirements. As described in our proposal, the EPA issued a final rule in November 2015, taking action on a comprehensive 2012 NSR SIP submittal from the ADEQ that constituted a major update to the ADEQ's NSR program (“2015 NSR action”). 80 FR 67319 (Nov. 2, 2015). The EPA's 2015 NSR action also included a separate limited approval of the ADEQ's NNSR program for PM <E T="52">10</E> only with respect to the West Pinal PM <E T="52">10</E> nonattainment area, based on the requirements of section 189(e) of the Act, without an accompanying limited disapproval. 80 FR 67319, 67332; see also 80 FR 14044, 14058, 14060 (Mar. 18, 2015) (proposed rulemaking for the 2015 NSR action). In the proposal for that action, the EPA observed that while the 2015 NSR action was generally SIP strengthening, CAA section 189(e) requires that the ADEQ's NNSR program for PM <E T="52">10</E> nonattainment areas apply to major stationary sources of PM <E T="52">10</E> precursors unless the EPA determines that such sources do not contribute significantly to PM <E T="52">10</E> levels which exceed the standard in the area. The NSR program did not apply to all precursors, and at that time, the EPA did not have the state's PM <E T="52">10</E> precursor analysis before us, and we could therefore not fully approve the 2012 NSR SIP submittal as complying with the CAA. 80 FR 14044, 14058. On December 15, 2023, the ADEQ submitted the “2023 Five Percent Particulate Plan for PM-10 for the West Pinal County Nonattainment Area” (“2023 PM <E T="52">10</E> Plan”) as a revision to the Arizona SIP, which includes a discussion of PM <E T="52">10</E> formation in the West Pinal PM <E T="52">10</E> nonattainment area and summarizes the State's PM <E T="52">10</E> precursor evaluation and determination that precursors do not contribute significantly to PM <E T="52">10</E> levels that exceed the NAAQS in the West Pinal PM <E T="52">10</E> nonattainment area. The EPA evaluated the State's PM <E T="52">10</E> precursor determination and concurred with the State's evaluation. Our proposal and TSD provide a more detailed discussion of our analysis supporting this determination. <HD SOURCE="HD1">II. Public Comments and EPA Responses</HD> The EPA's proposed action provided a 30-day public comment period. During this period, we received one comment. <SU>1</SU> <FTREF/> <FTNT> <SU>1</SU>  The comment was received on October 14, 2025, from a member of the public, and is available at <E T="03">www.regulations.gov</E> under docket number EPA-R09-OAR-2025-1113. </FTNT> The commenter stated, “I believe the proposal should not be approved, because public health surveys were not conducted.” The commenter stated that while the evidence in the State's PM <E T="52">10</E> precursor analysis “seems substantial,” a survey of citizens within the nonattainment area to address health concerns related to PM pollution should be conducted to allow citizens within the nonattainment area to express their concerns. The commenter noted that while the proposal was open to public comments, many citizens are not able to accurately express their concerns. The EPA acknowledges the commenter's concerns regarding health input from the public. This issue is outside the scope of the present rulemaking, and the EPA does not have the authority to compel such a survey in this context. In the SIP framework established under Title I of the CAA, heath impacts are evaluated in the process of setting the NAAQS. The states then choose how to regulate sources such that the NAAQS are attained. Section 109 of the CAA specifies that the primary NAAQS are set at a level “requisite to protect the public health” with “an adequate margin of safety.” The PM <E T="52">10</E> NAAQS at issue in this rulemaking was established in 1987 (52 FR 24634, July 1, 1987), and has been evaluated and retained multiple times since then. See 71 FR 61144 (Oct. 17, 2006), 78 FR 3085 (Jan 15, 2013), 85 FR 82684 (Dec. 18, 2020), 89 FR 16202 (Mar. 6, 2024). Once the NAAQS has been established and the states are tasked with regulating sources to ensure attainment of the NAAQS, states are generally not required to re-evaluate the health impacts of NAAQS pollutants. Under section 110(k)(3) “the Administrator shall approve” a complete SIP submittal “if it meets all of the applicable requirements of [the Act].” As explained in our proposal and TSD, the applicable Clean Air Act requirement for the purposes of this action is the section 189(e) requirement that “control requirements applicable under plans in effect under this part for major stationary sources of PM-10 shall also apply to major stationary sources of PM-10 precursors, except where the Administrator determines that such sources do not contribute significantly to PM-10 levels which exceed the standard in the area.” As outlined in the proposal and TSD, the EPA evaluated the State's precursor analysis and found their evidence and arguments sufficient to conclude that, for the purposes of NNSR permitting, precursors do not significantly contribute to PM <E T="52">10</E> formation in the West Pinal nonattainment area. The comment does not indicate that precursors contribute significantly to PM <E T="52">10</E> formation in West Pinal, and it is not clear how public survey information would assist in the EPA's section 189(e) determination regarding whether precursors contribute significantly to PM <E T="52">10</E> levels which exceed the standard in the area. Lastly, as noted by the commenter, all members of the public, including those in the West Pinal nonattainment area, were afforded the opportunity to comment on our proposal within the 30-day comment period. See CAA section 307(h). The public also had the opportunity to comment on the EPA's NAAQS evaluation actions. Although both the State and the EPA are free to conduct additional public engagement, the EPA may not condition its approval of a SIP submission on such additional public engagement. <HD SOURCE="HD1">III. EPA Action</HD> No comments were submitted that change our assessment as described in our proposed action. Therefore, as authorized in section 110(k)(3) of the Act, the EPA is approving the portion of the Arizona SIP under the Act that addresses NNSR permitting for precursor emissions from major stationary sources for purposes of the 1987 PM <E T="52">10</E> NAAQS in the West Pinal PM <E T="52">10</E> nonattainment area. As noted in our proposal, this resolves the issue that led the EPA to issue a limited approval in the 2015 NSR action, and this was the only remaining issue to be resolved regarding the full approvability of the ADEQ's NNSR program for PM <E T="52">10</E> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 14k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━