Air Plan Approval; Arizona; Interstate Transport Requirements for the 2012 Fine Particulate Matter National Ambient Air Quality Standard

ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 52</CFR> <DEPDOC>[EPA-R09-OAR-2025-0191; FRL-12978-01-R9]</DEPDOC> <SUBJECT>Air Plan Approval; Arizona; Interstate Transport Requirements for the 2012 Fine Particulate Matter National Ambient Air Quality Standard</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Environmental Protection Agency (EPA). <HD SOURCE="HED">ACTION:</HD> Proposed rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The Clean Air Act (CAA) requires each state implementation plan (SIP) to contain adequate provisions prohibiting emissions that will significantly contribute to nonattainment or interfere with maintenance of air quality in other states. The State of Arizona submitted SIP revisions to the Environmental Protection Agency (EPA) to address these requirements for the 2012 fine particulate (PM <E T="52">2.5</E> ) national ambient air quality standards (NAAQS). The EPA is proposing to approve Arizona's SIP submission as meeting the requirement that the Arizona SIP contains adequate provisions to prohibit emissions activity, within the State, from emitting air pollutants in amounts that will significantly contribute to nonattainment or interfere with maintenance of the 2012 PM <E T="52">2.5</E> NAAQS in any other state. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Comments must be received on or before November 24, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> Submit your comments, identified by Docket ID No. EPA-R09-OAR-2025-0191 at <E T="03">https://www.regulations.gov.</E> For comments submitted at <E T="03">Regulations.gov,</E> follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from <E T="03">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, please contact the person identified in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section. For 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> 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> Michael Dorantes, Geographic Strategies and Modeling Section (AIR 2-2), EPA Region IX, telephone number: (415) 972-3934, email address: <E T="03">dorantes.michael@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. Background</FP> <FP SOURCE="FP1-2">A. Statutory Background</FP> <FP SOURCE="FP1-2"> B. EPA's Interstate Transport Considerations for the 2012 PM <E T="52">2.5</E> NAAQS </FP> <FP SOURCE="FP-2">II. Arizona's Submittal</FP> <FP SOURCE="FP-2">III. The EPA's Evaluation</FP> <FP SOURCE="FP-2">IV. Proposed Action and Request for Public Comment</FP> <FP SOURCE="FP-2">V. Statutory and Executive Order Reviews</FP> </EXTRACT> <HD SOURCE="HD1">I. Background</HD> <HD SOURCE="HD2">A. Statutory Background</HD> On January 15, 2013 the EPA promulgated a revision to the PM <E T="52">2.5</E> NAAQS (2012 PM <E T="52">2.5</E> NAAQS), lowering the level of the primary standard to 12.0 µg/m <SU>3</SU> , while maintaining the secondary standard. <SU>1</SU> <FTREF/> Section 110(a)(1) of the CAA requires states to submit, within three years after promulgation of a new or revised NAAQS, SIP submissions meeting the applicable requirements of section 110(a)(2). <SU>2</SU> <FTREF/> Within CAA section 110(a)(2), are the requirements in CAA section 110(a)(2)(D)(i)(I), otherwise known as the “interstate transport” or “good neighbor” provision, which generally requires SIPs to contain adequate provisions to prohibit in-state emissions activities from having certain adverse air quality effects on other states due to interstate transport of air pollution. There are two so-called “prongs” within CAA section 110(a)(2)(D)(i)(I), which require that the SIP for a new or revised NAAQS contain adequate provisions prohibiting any source or other type of emissions activity within the state from emitting air pollutants in amounts that will significantly contribute to nonattainment of the NAAQS in another state (prong 1) or interfere with maintenance of the NAAQS in another state (prong 2). The EPA and states must give independent significance to prong 1 and prong 2 when evaluating downwind air quality problems under CAA section 110(a)(2)(D)(i)(I). <SU>3</SU> <FTREF/> <FTNT> <SU>1</SU>  78 FR 3086 (January 15, 2013). </FTNT> <FTNT> <SU>2</SU>  SIP revisions that are intended to meet the applicable requirements of section 110(a)(1) and (2) of the CAA are often referred to as infrastructure SIPs, and the applicable elements under section 110(a)(2) are referred to as infrastructure requirements. </FTNT> <FTNT> <SU>3</SU>  See <E T="03">North Carolina</E> v. <E T="03">EPA,</E> 531 F.3d 896, 909-911 (D.C. Cir. 2008). </FTNT> <HD SOURCE="HD2"> B. EPA's Interstate Transport Considerations for the 2012 PM <E T="54">2.5</E> NAAQS </HD> The EPA has addressed the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) with respect to the PM <E T="52">2.5</E> NAAQS in several regulatory actions. In 2011, the EPA promulgated the Cross-State Air Pollution Rule (CSAPR) to address the obligations of states under prongs 1 and 2 to prohibit air pollution from contributing significantly to nonattainment in, or interfering with the maintenance of, any other state with regard to several NAAQS, including the 1997 annual and 2006 24-hour PM <E T="52">2.5</E> NAAQS. <SU>4</SU> <FTREF/> In that rule, we used an air quality threshold of one percent of the applicable PM <E T="52">2.5</E> NAAQS to link contributing states to projected nonattainment or maintenance air quality monitors ( <E T="03">i.e.,</E> receptors). If air quality modeling projected that an upwind state contributed more than the one percent threshold to a downwind receptor, we determined that the state was “linked.” On September 13, 2013, the EPA issued the “Guidance on Infrastructure State Implementation Plan (SIP) Elements under Clean Air Act Sections 110(a)(1) and 110(a)(2)” (“2013 I-SIP Guidance”) for the development of infrastructure SIPs for several NAAQS including the 2012 PM <E T="52">2.5</E> standard. <SU>5</SU> <FTREF/> On March 12, 2016, the EPA issued the memorandum titled “Information on the Interstate Transport “Good Neighbor” Provision for the 2012 Fine Particulate Matter National Ambient Air Quality Standards under Clean Air Act Section 110(a)(2)(D)(i)(I)” (“2016 PM <E T="52">2.5</E> Transport Memo”), specifically developed for the infrastructure SIP transport requirements for the 2012 PM <E T="52">2.5</E> NAAQS. <SU>6</SU> <FTREF/> Using CSAPR, the 2013 I-SIP guidance, and the 2016 PM <E T="52">2.5</E> Transport Memo, we have developed a consistent framework for evaluating the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) for the 2012 PM <E T="52">2.5</E> NAAQS, and outlined a four-step process to evaluate the obligations under interstate transport provision under 110(a)(2)(D)(i)(I), which includes: <FTNT> <SU>4</SU>  76 FR 48208 (August 8, 2011). </FTNT> <FTNT> <SU>5</SU>  Memorandum dated September 13, 2013 from Stephen D. Page, Director, Office of Air Quality and Planning Standards, U.S. EPA, to Regional Air Division Directors, Regions 1-10, Subject: “Guidance on Infrastructure State Implementation Plan (SIP) Elements under Clean Air Act Sections 110(a)(1) and 110(a)(2).” </FTNT> <FTNT> <SU>6</SU>  Memorandum dated March 17, 2016, from Stephen D. Page, Director, Office of Air Quality and Planning Standards, U.S. EPA, to Regional Air Division Directors, Regions 1-10, Subject: “Information on the Interstate Transport “Good Neighbor” Provision for the 2012 Fine Particulate Matter National Ambient Air Quality Standards under Clean Air Act Section 110(a)(2)(D)(i)(I).” </FTNT> (1) Identifying downwind receptors that are expected to have problems attaining or maintaining the NAAQS; (2) Identifying which upwind states contribute to these identified problems in amounts sufficient to warrant further review and analysis; (3) For states identified as contributing to downwind air quality problems, identifying upwind emissions reductions necessary to prevent an upwind state from significantly contributing to nonattainment or interfering with maintenance of the NAAQS downwind; (4) For states that are found to have emissions that significantly contribute to nonattainment or interfere with maintenance of the NAAQS downwind, reducing the identified upwind emissions through adoption of permanent and enforceable measures. To satisfy Step 1 of the interstate framework, the 2016 PM <E T="52">2.5</E> Transport Memo provides annual PM <E T="52">2.5</E> design values for monitors in the United States based on quality-assured and certified ambient air ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 19k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━