# Air Plan Approval; Arizona; Interstate Transport Requirements for the 2012 Fine Particulate Matter National Ambient Air Quality Standard
**AGENCY:**
Environmental Protection Agency (EPA).
**ACTION:**
Proposed rule.
**SUMMARY:**
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 <sub>2.5</sub> ) 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 <sub>2.5</sub> NAAQS in any other state.
**DATES:**
Comments must be received on or before November 24, 2025.
**ADDRESSES:**
Submit your comments, identified by Docket ID No. EPA-R09-OAR-2025-0191 at *https://www.regulations.gov.* For comments submitted at *Regulations.gov,* follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from *Regulations.gov* . 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 ( *i.e.,* on the web, cloud, or other file sharing system). For additional submission methods, please contact the person identified in the *FOR FURTHER INFORMATION CONTACT* section. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit *https://www.epa.gov/dockets/commenting-epa-dockets.* 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 *FOR FURTHER INFORMATION CONTACT* section.
**FOR FURTHER INFORMATION CONTACT:**
Michael Dorantes, Geographic Strategies and Modeling Section (AIR 2-2), EPA Region IX, telephone number: (415) 972-3934, email address: *[email protected].*
**SUPPLEMENTARY INFORMATION:**
Throughout this document, “we,” “us,” and “our” refer to the EPA.
**Table of Contents**
I. Background
A. Statutory Background
B. EPA's Interstate Transport Considerations for the 2012 PM <sub>2.5</sub> NAAQS
II. Arizona's Submittal
III. The EPA's Evaluation
IV. Proposed Action and Request for Public Comment
V. Statutory and Executive Order Reviews
**I. Background**
**A. Statutory Background**
On January 15, 2013 the EPA promulgated a revision to the PM <sub>2.5</sub> NAAQS (2012 PM <sub>2.5</sub> NAAQS), lowering the level of the primary standard to 12.0 µg/m <sup>3</sup> , while maintaining the secondary standard. [^1] 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). [^2] 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). [^3]
[^1] 78 FR 3086 (January 15, 2013).
[^2] 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.
[^3] See *North Carolina* v. *EPA,* 531 F.3d 896, 909-911 (D.C. Cir. 2008).
**B. EPA's Interstate Transport Considerations for the 2012 PM
2.5
NAAQS**
The EPA has addressed the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) with respect to the PM <sub>2.5</sub> 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 <sub>2.5</sub> NAAQS. [^4] In that rule, we used an air quality threshold of one percent of the applicable PM <sub>2.5</sub> NAAQS to link contributing states to projected nonattainment or maintenance air quality monitors ( *i.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 <sub>2.5</sub> standard. [^5] 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 <sub>2.5</sub> Transport Memo”), specifically developed for the infrastructure SIP transport requirements for the 2012 PM <sub>2.5</sub> NAAQS. [^6] Using CSAPR, the 2013 I-SIP guidance, and the 2016 PM <sub>2.5</sub> 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 <sub>2.5</sub> NAAQS, and outlined a four-step process to evaluate the obligations under interstate transport provision under 110(a)(2)(D)(i)(I), which includes:
[^4] 76 FR 48208 (August 8, 2011).
[^5] 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).”
[^6] 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).”
(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 <sub>2.5</sub> Transport Memo provides annual PM <sub>2.5</sub> design values for monitors in the United States based on quality-assured and certified ambient air quality monitoring data. For each ambient monitoring site, the EPA calculated the projected average design value and projected maximum design values for the then future projection years of 2017 and 2025. In total, the 2016 PM <sub>2.5</sub> Transport Memo identified 17 California monitoring sites located in the San Joaquin Valley and the South Coast nonattainment areas, one site in Shoshone County, Idaho, and one site in Allegheny County, Pennsylvania as having projected 2017 and 2025 average and/or maximum future year PM <sub>2.5</sub> design values above the 2012 PM <sub>2.5</sub> NAAQS. The modeled annual PM <sub>2.5</sub> projections for the years 2017 and 2025 evaluated projected air quality relative to the 2012 PM <sub>2.5</sub> NAAQS and are therefore consistent with Step 1 of the four-step interstate framework originally used in CSAPR. This rulemaking considers these receptors, as well as additional analysis conducted by the State and the EPA when evaluating step 2 of the framework as to whether emissions from Arizona contribute to nonattainment or interfere with maintenance of the PM <sub>2.5</sub> NAAQS, and whether further evaluation under steps 3 and 4 are necessary.
**II. Arizona's Submittal**
The Arizona Department of Environmental Quality (ADEQ) submitted two SIP revisions to address the infrastructure SIP requirements in CAA sections 110(a)(1) and 110(a)(2) for the 2012 PM <sub>2.5</sub> NAAQS. On December 11, 2015, ADEQ submitted the “Arizona State Implementation Plan Revision for the 2012 Fine Particulate Matter (PM <sub>2.5</sub> ) National Ambient Air Quality Standard” (“2015 PM <sub>2.5</sub> I-SIP Submittal). [^7] On February 10, 2022, ADEQ submitted the “State Implementation Plan Revision: Clean Air Act Section 110(a)(2) for the 2012 Fine Particulate & 2015 Ozone NAAQS” (“2022 I-SIP Supplement”). [^8] The submittals collectively address the requirements of 110(a)(2)(D)(i)(I) as described by this proposed rulemaking. We refer to them collectively herein as “Arizona's 2012 PM <sub>2.5</sub> I-SIP submittals.” We find that Arizona's 2012 PM <sub>2.5</sub> I-SIP submittals meet the procedural requirements for public participation under CAA section 110(a)(2) and 40 CFR 51.102. [^9] We have previously proposed or finalized actions on these submittals except for those portions of the 2012 PM <sub>2.5</sub> I-SIP submittals addressing prongs 1 and 2 of the interstate transport requirements under 110(a)(2)(D)(i)(I). [^10] Herein, we are proposing action on these submittals with respect to the 110(a)(2)(D)(i)(I) interstate transport requirements for the 2012 PM <sub>2.5</sub> NAAQS.
[^7] Letter dated December 11, 2015, from Eric Massey, Director, Air Quality Division, ADEQ, to Jared Blumenfeld, Regional Administrator, EPA Region IX, Subject “Arizona Infrastructure State Implementation Plan for the 2012 PM <sub>2.5</sub> National Ambient Air Quality Standards.”
[^8] Letter dated February 10, 2022, from Daniel Czecholinski, Director, Air Quality Division, ADEQ, to Martha Guzman, Regional Administrator, EPA Region IX, Subject: “Submittal of the Arizona State Implementation Plan Revision under Clean Air Act Sections 110(a)(2) for the 2012 Fine Particulate and the 2015 Ozone NAAQS.”
[^9] For the 2015 PM <sub>2.5</sub> I-SIP submittal, ADEQ provided a 30-day public comment period that started on November 9, 2015, and concluded on December 9, 2015, with a public hearing occurring on the same date. No comments were expressed during the 30-day comment period no at the public hearing, The details of this public comment period and hearing can be found in appendix B of the 2015 PM <sub>2.5</sub> I-SIP submittal. Similarly, for the 2022 I-SIP supplement, ADEQ provided a 30-day public comment period between December 13, 2021, and January 13, 2022, with a public hearing occurring on January 13, 2022. ADEQ received no verbal nor written comments on the 2022 I-SIP supplement. The details of this public comment period and hearing can be found in appendix E to the 2022 I-SIP supplement.
[^10] 89 FR 50245, June 13, 2024 and 89 FR 102744, December 18, 2024.
**III. The EPA's Evaluation**
We have evaluated Arizona's 2012 PM <sub>2.5</sub> I-SIP submittals for compliance with the infrastructure SIP requirements of CAA section 110(a)(2)(D)(i)(I) and the applicable regulations of 40 CFR part 51 (“Requirements for Preparation, Adoption, and Submittal of State Implementation Plans”). The technical support document (TSD) for this rulemaking is available in the docket and includes our detailed evaluation of direct and precursor emissions of PM <sub>2.5</sub> within Arizona and from other sources, geographical information, climatological information, and topographical information such as terrain and its potential effect on transport of pollutants. Considering the weight of the evidence, the EPA agrees with the conclusion drawn by Arizona in the 2012 PM <sub>2.5</sub> I-SIP submittals that emissions from sources in Arizona will not significantly contribute to nonattainment or interfere with the maintenance of the 2012 PM <sub>2.5</sub> NAAQS in any other state. In particular, the EPA finds that Arizona is not “linked” to any out-of-state receptors, and as such, the State is not required to perform the last two steps of the four-step framework outlined in the EPA's interstate transport guidance and rulemakings.
**IV. Proposed Action and Request for Public Comment**
Based on the EPA's weight-of-evidence evaluation summarized in this document and fully detailed in the accompanying TSD, the EPA proposes to approve Arizona's 2012 PM <sub>2.5</sub> I-SIP submittals with respect to the 2012 PM <sub>2.5</sub> NAAQS for the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I). The EPA is soliciting public comments on this proposed rulemaking. We will accept comments from the public for the next 30 days. We will consider any comments received before taking final action.
**V. Statutory and Executive Order Reviews**
Under the CAA, the Administrator is required to approve a SIP submission that complies with the provisions of the Act and applicable federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, the EPA's role is to approve state choices, provided that they meet the criteria of the CAA. Accordingly, this proposed action merely proposes to approve state law as meeting federal requirements and does not impose additional requirements beyond those imposed by state law. For that reason, this proposed action:
• Is not a significant regulatory action subject to review by the Office of Management and Budget under Executive Order 12866 (58 FR 51735, October 4, 1993);
• Is not subject to Executive Order 14192 (90 FR 9065, February 6, 2025) because SIP actions are exempt from review under Executive Order 12866;
• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 *et seq.* );
• Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 *et seq.* );
• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4);
• Does not have federalism implications as specified in Executive Order 13132 (64 FR 43255, August 10, 1999);
• Is not subject to Executive Order 13045 (62 FR 19885, April 23, 1997) because it proposes to approve a state program;
• Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001); and
• Is not subject to requirements of section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the CAA.
In addition, the SIP is not approved to apply on any Indian reservation land or in any other area where the EPA or an Indian Tribe has demonstrated that a Tribe has jurisdiction. In those areas of Indian country, the rule does not have Tribal implications and will not impose substantial direct costs on Tribal governments or preempt Tribal law as specified by Executive Order 13175 (65 FR 67249, November 9, 2000).
**List of Subjects in 40 CFR Part 52**
Environmental protection, Air pollution control, Incorporation by reference, Intergovernmental relations, Nitrogen dioxide, Ozone, Particulate matter, Reporting and recordkeeping requirements, Volatile organic compounds.
**Authority:**
42 U.S.C. 7401 *et seq.*
Dated: October 14, 2025.
Cheree D. Peterson,
Acting Regional Administrator, Region IX.