SUPPLEMENTARY INFORMATION:

Throughout this document, “we,” “us,” and “our” refer to the EPA. We use multiple abbreviations and terms in this proposed rule. While this list may not be exhaustive, for ease of reading and for reference purposes, the EPA defines the following terms and acronyms here:

AAC—Arizona Administrative Code

ADEQ—Arizona Department of Environmental Quality

AgBMP—agricultural best management practices

A.R.S.—Arizona Revised Statures

BACM—best available control measures

BMP—best management practices

CAA—Clean Air Act

CBI—confidential business information

CFR—Code of Federal Regulations

EPA—Environmental Protection Agency

NAAQS—national ambient air quality standards

PM—particulate matter

PM₁₀ —particulate matter less than 10 μm in diameter

SIP—State Implementation Plan

TSD—technical support document

Table of Contents

I. Executive Summary ( printed page 66041)

A. What Action is the EPA Taking?

B. What is the Legal Authority and What are the Requirements?

II. Background

III. Summary of Arizona's Submittal

IV. The EPA's Evaluation of Arizona's Submittal

A. How is the EPA Evaluating the Submittal?

B. Does the Submittal Meet the Evaluation Criteria?

C. Proposed Action and Public Comment

V. Incorporation by Reference

VI. Statutory and Executive Order Reviews

I. Executive Summary

A. What Action is the EPA Taking?

The EPA is proposing to approve an August 13, 2026, SIP submittal from Arizona that requests to add two rules to the Arizona SIP. The rules relate to Arizona's Agricultural Best Management Practices (AgBMP) program and are from the Arizona Administrative Code (AAC): Title 18, Chapter 2, Section 610.03, “Agricultural PM General Permit for Crop Operations; Pinal County PM Nonattainment Area,” amended April 2, 2026 (“R18-2-610.03”), and R18-2-611.03, “Agricultural PM General Permit for Animal Operations: Pinal County PM Nonattainment Area,” amended April 2, 2026 (“R18-2-611.03”). These rules only apply within the West Pinal County PM₁₀ nonattainment area within Pinal County, Arizona, and were submitted to support the State's attainment plan for the area, including the requirement to meet the Best Available Control Measures (BACM) requirement. Previously, the EPA proposed, but did not finalize, a limited approval and limited disapproval of earlier versions of these two rules.^[1] The rules were recently revised by Arizona's AgBMP Committee and we are now proposing to fully approve them under the CAA.

R18-2-610.03 regulates PM₁₀ emissions from commercial crop operations in the West Pinal County PM₁₀ nonattainment area. R18-2-611.03 regulates PM₁₀ emissions from commercial dairy operations, beef cattle feedlots, commercial poultry facilities, and commercial swine facilities in the West Pinal County PM₁₀ nonattainment area. Both rules require operators to implement best management practices (BMPs) selected from regulatory menus to reduce fugitive PM₁₀ emissions from their operations. If finalized as proposed, R18-2-610.03 and R18-2-611.03 would be incorporated into the federally enforceable portion of the Arizona SIP.

B. What is the legal authority and what are the requirements?

We are taking this proposed action under section 110 of the CAA. Pursuant to CAA section 110(a), States are required to submit SIPs to the EPA that provide for the implementation, maintenance, and enforcement of the national ambient air quality standards (NAAQS). CAA section 110(k) requires SIPs to meet certain procedural requirements and requires the EPA to approve or disapprove SIP submissions. CAA section 110(l) requires States to provide public notice and an opportunity for public hearing of SIP revisions prior to their submittal and prohibits the EPA from approving any SIP revisions that would interfere with attainment or maintenance of a NAAQS, reasonable further progress, or other applicable requirements of the CAA. If a SIP submittal meets all the applicable CAA requirements, then the EPA must approve the submittal under CAA section 110(k)(3).

For this submittal to be approved, we must consider CAA requirements related to the emission limitations in the submitted rules. CAA sections 110(a)(2)(A) and 302(k) require emission limitations in the SIP to be enforceable and continuous, respectively. CAA section 172(c)(6) requires SIPs for nonattainment areas “include enforceable emission limitations, and such other control measures means or techniques . . . as well as schedules and timetables for compliance, as may be necessary or appropriate to provide for attainment of such standard in such area by the applicable attainment date . . . .” Also, 40 CFR part 51, subpart K requires SIPs to contain legally enforceable procedures for monitoring the status of compliance with the requirements in the control strategy. While these rules were submitted to meet BACM requirements under CAA section 189(b)(1)(B), we are not evaluating them for BACM in this action. The EPA will evaluate BACM in an upcoming action on the attainment plan for the West Pinal County PM₁₀ nonattainment area.

We are proposing that this submittal meets all applicable CAA requirements and are proposing to fully approve it under CAA section 110(k)(3).

II. Background

R18-2-610.03 and R18-2-611.03 regulate emissions of PM, including PM₁₀, which contribute to effects that are harmful to human health and the environment, including premature mortality, aggravation of respiratory and cardiovascular disease, decreased lung function, visibility impairment, and damage to vegetation and ecosystems. Section 110(a) of the CAA requires States to submit regulations that control PM emissions, as necessary to meet the requirements of the Act.

Previously, on January 17, 2025, we proposed a limited approval and limited disapproval of earlier versions of R18-2-610.03 and R18-2-611.03 (“January 2025 AgBMP proposal”), finding that the rules strengthened the SIP but identifying enforceability and rule clarity concerns.^[2] Following that proposal, the Arizona AgBMP Committee revised both rules and ADEQ resubmitted them to the EPA. The updated rules are the subject of this proposal.

The January 2025 AgBMP proposal also included proposing to fully approve two related AgBMP definitions rules and the AgBMP statute: AAC R18-2-610, “Definitions for R18-2-610.01, R18-2-610.02, and R18-2-610.03,” amended November 26, 2021; AAC R18-2-611, “Definitions for R18-2-611.01, R18-2-611.02, and R18-2-611.03,” amended November 26, 2021; and A.R.S. section 49-457. These provisions are not addressed in this proposed rulemaking, and we are not requesting comment on them.

We intend to concurrently finalize action on the January 2025 AgBMP proposal with our final action on this rulemaking.

III. Summary of Arizona's Submittal

On August 13, 2026, ADEQ submitted R18-2-610.03 and R18-2-611.03 to the EPA for approval into the Arizona SIP. Table 1 of this document lists the rules addressed by this proposal with the dates that they were adopted by the Arizona Agricultural Best Management Practices (AgBMP) Committee and submitted to the EPA by the ADEQ. ( printed page 66042)

Under CAA section 110(k)(1), the EPA must determine whether a SIP submittal meets the minimum completeness criteria established in 40 CFR part 51, appendix V for an official SIP submittal on which the EPA is obligated to take action. We find that the ADEQ's August 13, 2026 SIP submittal for AAC R18-2-610.03 and AAC R18-2-611.03 meets the completeness criteria in 40 CFR part 51 Appendix V. These rules apply within the West Pinal County PM₁₀ nonattainment area in Pinal County, Arizona, that is classified as “Serious” nonattainment for the PM₁₀ NAAQS. R18-2-610.03 regulates PM₁₀ emissions from commercial crop operations in the West Pinal County PM₁₀ nonattainment area. R18-2-611.03 regulates PM₁₀ emissions from commercial dairy operations, beef cattle feedlots, commercial poultry facilities, and commercial swine facilities in the West Pinal County PM₁₀ nonattainment area. Both rules require operators to implement BMPs selected from regulatory menus to reduce fugitive PM₁₀ emissions from their operations.

We approved an earlier version of R18-2-610.03 into the Arizona SIP on May 1, 2017.^[3] The State has specified that the present submission of R18-2-610.03 is intended to replace this previously-approved version of R18-2-610.03 in the SIP. This submission was also intended to supersede the version of the rule that was submitted on March 3, 2023. R18-2-611.03 was initially adopted by the Arizona AgBMP Committee on November 26, 2021 and submitted to the EPA on March 3, 2023. The State has withdrawn that version of the rule and has requested us to include in the SIP the April 2, 2026 version of the rule instead.

IV. The EPA's Evaluation of Arizona's Submittal

A. How is the EPA evaluating the submittal?

Emission limitations in the SIP must be enforceable and continuous, and SIP revisions must not interfere with applicable requirements concerning attainment and reasonable further progress or other CAA requirements.^[4] Additionally, 40 CFR part 51, subpart K requires SIPs to contain enforceable procedures for monitoring the status of compliance with the requirements in the control strategy. Our evaluation considered relevant guidance and policy documents.^[5]

The West Pinal County nonattainment area is classified as Serious for the PM₁₀ NAAQS.^[6] Generally, SIPs for Serious PM₁₀ nonattainment areas must implement BACM, including Best Available Control Technology.^[7] This evaluation is generally performed in the context of a broader attainment plan. Accordingly, we will not evaluate these rules for BACM as part of this proposed action and will instead do so in a separate, upcoming planning action for the West Pinal PM₁₀ nonattainment area.

B. Does the submittal meet the evaluation criteria?

We evaluated these rules to ensure they meet CAA requirements and are consistent with relevant guidance regarding enforceability and SIP revisions.

With respect to emission limitations being enforceable and continuous, the revised rules specify clear requirements, providing regulatory certainty to the regulated community. The rules' implementation details are also sufficient for State enforcement, and emission limits apply on a continuous basis. The resubmitted rules require annual, non-anonymous reporting of BMP selections and certifications directly to ADEQ (or through the Arizona Department of Agriculture as an optional intermediary for crop operations), with form contents that include identifying BMP selections for the upcoming year, area and crop/operation identification, and certification of prior-year implementation. These requirements enable ADEQ to identify which BMPs each operator has committed to implement, verify implementation during inspections, and document noncompliance on an individual operator basis. These revisions strengthen the clarity and enforceability of the rules, address the concerns identified in our January 2025 AgBMP proposal, and meet the relevant CAA enforceability requirements.

With respect to SIP revisions under CAA section 110(l), approval of the revised rules would not interfere with any applicable CAA requirements, including requirements for reasonable further progress and attainment. R18-2-610.03 is more stringent than the current SIP-approved version of R18-2-610.03, requiring two BMPs per category, adding new BMP categories, and adding a new 20 percent opacity limit for high-traffic unpaved areas. R18-2-611.03 is a new rule with respect to the Arizona SIP and is thus a substantial strengthening. The rules do not interfere with any other relevant CAA requirements. The EPA's technical support document (TSD) has more information about these rules.

Based on our review, the rules meet the relevant CAA requirements.

C. Proposed Action and Public Comment

As authorized in section 110(k)(3) of the CAA, the EPA proposes to approve the submitted rules because they fulfill all relevant requirements. We will accept comments from the public on this proposal until November 18, 2026. If we finalize approval, our final action will incorporate these rules into the federally enforceable SIP.

Specifically, the EPA is proposing to approve AAC R18-2-610.03, “Agricultural PM General Permit for Crop Operations; Pinal County PM Nonattainment Area,” and AAC R18-2- ( printed page 66043) 611.03, “Agricultural PM General Permit for Animal Operations; Pinal County PM Nonattainment Area,” as revised on April 2, 2026, and submitted by ADEQ on May 15, 2026. If we finalize this proposed approval, the April 2, 2026 version of AAC R18-2-610.03 will replace the previously SIP-approved version of this rule,^[8] and AAC R18-2-611.03 will be newly added to the Arizona SIP.

This proposed approval supersedes, with respect to AAC R18-2-610.03 and AAC R18-2-611.03, the proposed limited approval and limited disapproval of earlier versions of these rules from the 2025 AgBMP proposal. This proposal does not change our analysis and proposal with respect to A.R.S. section 49-457, AAC R18-2-610, or AAC R18-2-611 from the January 2025 AgBMP proposal.

V. Incorporation by Reference

In this document, the EPA is proposing to include in a final EPA rule, regulatory text that includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, the EPA is proposing to incorporate by reference AAC R18-2-610.03, “Agricultural PM General Permit for Crop Operations; Pinal County PM Nonattainment Area,” amended April 2, 2026, which regulates PM₁₀ emissions from commercial crop operations in the West Pinal County PM₁₀ nonattainment area; and AAC R18-2-611.03, “Agricultural PM General Permit for Animal Operations; Pinal County PM Nonattainment Area,” as revised April 2, 2026, which regulates PM₁₀ emissions from commercial dairy operations, beef cattle feedlots, poultry facilities, and swine facilities in the West Pinal County PM₁₀ nonattainment area. The EPA has made, and will continue to make, these materials available through www.regulations.gov and at the EPA Region IX Office (please contact the person identified in the FOR FURTHER INFORMATION CONTACT section of this preamble for more information).

VI. Statutory and Executive Order Reviews

Under the Clean Air Act, the Administrator is required to approve a SIP submission that complies with the provisions of the Clean Air 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 Clean Air Act. Accordingly, this proposed action merely proposes approval of State law as meeting Federal requirements and does not impose additional requirements beyond those imposed by State law. For that reason, this action:

• Is not a significant regulatory action subject to review by the Office of Management and Budget underExecutive Order 12866 (58 FR 51735, October 4, 1993);
• Is not anExecutive Order 14192 (90 FR 9065, February 6, 2025) regulatory action because this proposed action is not significant 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 inExecutive Order 13132 (64 FR 43255, August 10, 1999);
• Is not subject toExecutive Order 13045 (62 FR 19885, April 23, 1997) because it approves a State program;
• Is not a significant regulatory action subject toExecutive 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 Clean Air Act.

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).

Authority: 42 U.S.C. 7401 et seq.

91 FR 66040