SUPPLEMENTARY INFORMATION:

Throughout this document, “we,” “us,” and “our” refer to the EPA.

Table of Contents

I. Background

II. The State's Submittal

III. The EPA's Evaluation

A. How is the EPA evaluating the document?

B. Does the document meet the evaluation criteria?

IV. Proposed Action and Request for Public Comment

V. Statutory and Executive Order Reviews

I. Background

Pursuant to title I of the CAA, the EPA establishes ambient air quality standards for six “criteria” air pollutants known to be harmful to human health and the environment. States are required to submit plans, referred to as SIPs, that provide for implementation, maintenance, and enforcement of each standard. As appropriate, this includes measures to reduce emissions of criteria air pollutants and/or “precursor” air pollutants that lead to the formation of the criteria air pollutants. Areas causing or contributing to a violation of a NAAQS are designated under the CAA as “nonattainment” and must adopt and submit additional SIP elements. Ozone nonattainment areas are further classified as “Marginal,” “Moderate,” “Serious,” “Severe,” or “Extreme.”

In ozone nonattainment areas, one of the additional SIP elements is the submission of a RACT SIP. CAA sections 182(b)(2) and 182(f) require RACT to be implemented in ozone nonattainment areas classified as Moderate or higher for any source category covered by a Control Techniques Guidelines (CTG) document issued by the EPA and for any major stationary source of volatile organic compounds (VOC) and oxides of nitrogen (NO_X ).^[1] The EPA defines RACT as the “. . . lowest emission limitation that a particular source is capable of meeting by the application of control technology that is reasonably available considering technological and economic feasibility.” ^[2]

In this proposal, we are evaluating a RACT SIP submitted by Arizona. In 2015, the EPA revised the ozone NAAQS establishing an 8-hour standard of 0.070 parts per million (“2015 ozone NAAQS” or “2015 standard”).^[3] In 2018, the EPA initially designated the Phoenix-Mesa area in Arizona as nonattainment for the 2015 standard with a classification of Marginal.^[4] In 2022, the EPA reclassified the Phoenix-Mesa ozone nonattainment area to Moderate.^[5] The reclassification to Moderate triggered the CAA requirement for Arizona to implement RACT in the Phoenix-Mesa ozone ( printed page 6558) nonattainment area for the 2015 standard.^[6]

II. The State's Submittal

On March 26, 2025, the Arizona Department of Environmental Quality (ADEQ) submitted a SIP revision to the EPA certifying that RACT requirements for the portion of Gila County within the Phoenix-Mesa ozone nonattainment area have been met (“2025 RACT SIP” or “submittal”). The ADEQ is the governor's designee for submitting official revisions of the Arizona SIP to the EPA. Table 1 lists the document in the submittal that is addressed by this proposal with the date that it was adopted and submitted to the EPA by the ADEQ.

On May 1, 2025, the EPA determined that ADEQ's 2025 RACT SIP met the completeness criteria in 40 CFR part 51, appendix V.

The ADEQ has jurisdiction for regulating stationary sources of air pollution within Gila County, Arizona. Therefore, consistent with CAA sections 182(b)(2) and 182(f), the 2025 RACT SIP must demonstrate that the ADEQ is implementing RACT in this area for all sources covered by a CTG document and for all major stationary sources of VOC or NO_X . Because the Phoenix-Mesa ozone nonattainment area is classified as Moderate, a major stationary source is any stationary facility or source of air pollutants which directly emits, or has the potential to emit, one hundred tons per year or more of any air pollutant.^[7]

The ADEQ's 2025 RACT SIP certifies that there are no sources subject to RACT requirements within the Gila County portion of the Phoenix-Mesa ozone nonattainment area for the 2015 ozone NAAQS. As such, the ADEQ submitted negative declarations for all CTG documents and for major stationary sources of VOC and NO_X . The ADEQ based its negative declarations on reviewing its permitting database, internal point source emissions inventory, and the EPA National Emissions Inventory (NEI). The ADEQ stated that “[t]here are currently no air permitted sources within the area.” ^[8] The EPA's technical support document (TSD) in the docket for this action has more information about the ADEQ's 2025 RACT SIP.

III. The EPA's Evaluation

A. How is the EPA evaluating the document?

The ADEQ's 2025 RACT SIP must demonstrate that it implements RACT in the Gila County portion of the Phoenix-Mesa ozone nonattainment area. The EPA's implementation rule for the 2015 standard provides guidance for making a RACT demonstration and references prior discussions in our implementation rules for the 1997 and 2008 ozone standards.^[9] In sum, RACT SIPs must contain adopted RACT regulations, certifications (where appropriate) that existing provisions are RACT, and/or negative declarations that no sources in the nonattainment area are covered by a specific CTG.^[10] Furthermore, states must submit appropriate supporting information for their RACT submissions.^[11]

Additionally, relevant requirements in CAA sections 110(a) and 110(l) must also be met. CAA section 110(a) requires emissions limitations in the SIP to be “enforceable.” CAA section 110(l) requires SIP revisions to be adopted after reasonable notice and public hearing and prohibits EPA approval if the revision would interfere with any applicable requirement concerning attainment and reasonable further progress or any other applicable requirement of the Act.

Rules, guidance, and policy documents that we used for our review include the following:

1. “State Implementation Plans; General Preamble for the Implementation of Title I of the Clean Air Act Amendments of 1990,” 57 FR 13498 (April 16, 1992); 57 FR 18070 (April 28, 1992).

2. Memorandum dated May 18, 2006, from William T. Harnett, Director, Air Quality Policy Division, to Regional Air Division Directors, Subject: “RACT Qs & As—Reasonably Available Control Technology (RACT): Questions and Answers.”

3. “Final Rule to Implement the 8-hour Ozone National Ambient Air Quality Standard—Phase 2,” 70 FR 71612 (November 29, 2005).

4. “Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State Implementation Plan Requirements,” 80 FR 12264 (March 6, 2015).

5. “Implementation of the 2015 National Ambient Air Quality Standards for Ozone: Nonattainment Area State Implementation Plan Requirements,” 83 FR 62998 (December 6, 2018).

B. Does the document meet the evaluation criteria?

We evaluated the ADEQ's 2025 RACT SIP to ensure it meets RACT and other CAA requirements. We reviewed the EPA's NEI, reviewed the EPA's Enforcement and Compliance History Online (ECHO) database, and performed multiple internet searches for sources potentially located within the nonattainment area to determine whether the ADEQ's determination that no sources are subject to RACT was reasonable.

We did not identify any major stationary sources of VOC or NO_X or any sources subject to a CTG document within the Gila County portion of the Phoenix-Mesa ozone nonattainment area. Given that no air permits have been issued for stationary sources within this area of Gila County, this is a reasonable finding. Additionally, this conclusion is not unexpected considering the portion of Gila County in the Phoenix-Mesa ozone nonattainment area represents less than 0.5 percent of the entire acreage of the nonattainment area, and the land is entirely National Forest and National Park land.

Thus, we did not identify any sources that would be subject to RACT requirements, and we agree with the ADEQ's submitted negative declarations. We also find that the submittal meets CAA section 110(l) because it was adopted after reasonable notice and public hearing and because it would not interfere with any applicable requirement concerning attainment, reasonable further progress, or any other applicable requirement of ( printed page 6559) the Act. Because only negative declarations were adopted, the submittal does not contain any emissions limitations to evaluate for enforceability under CAA section 110(a). The TSD has more information on our evaluation.

IV. Proposed Action and Request for Public Comment

As authorized in section 110(k)(3) of the Act, the EPA proposes to approve the ADEQ's 2025 RACT SIP under CAA sections 182(b)(2) and 182(f) as meeting RACT for the Gila County portion of the Phoenix-Mesa ozone nonattainment area for the 2015 ozone NAAQS and because it fulfills the relevant requirements in CAA sections 110(a) and 110(l). For each RACT element, Table 2 lists the rule or negative declaration relied upon to address RACT and our proposed action for that RACT element.

We will accept comments from the public on this proposal until March 16, 2026. If finalized as proposed, our final action will add the document in Table 1 into the Arizona SIP and the negative declarations into 40 CFR 52.122.

Table 2—Proposed Action on RACT Elements for 2015 Ozone NAAQS ^[12]

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 underExecutive Order 12866 (58 FR 51735, October 4, 1993);
• Is not subject toExecutive 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 ( printed page 6561) 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 proposes to approve 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 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).

91 FR 6557