SUPPLEMENTARY INFORMATION:

Throughout this proposed rule, the use of “we,” “us,” or “our” is intended to 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:

ADEQ—Arizona Department of Environmental Quality

A.R.S.—Arizona Revised Statutes

CAA—Clean Air Act

CARB—California Air Resources Board

CBI—Confidential Business Information

CTG—Control Technology Guideline

FIP—Federal Implementation Plan

GDF—Gas Dispensing Facility

MCAQD—Maricopa County Air Quality Department

NAAQS—National Ambient Air Quality Standards

RACT—Reasonably Available Control Technology

SIP—State Implementation Plan

TSD—Technical Support Document

VOC—Volatile Organic Compounds

Table of Contents

I. Executive Summary

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?

1. Prior Deficiencies in Rule 352

2. Prior Deficiencies in Rule 353

3. New Deficiencies in Rule 353

C. The EPA's Recommendations

D. Proposed Action and Public Comment

III. Incorporation by Reference

IV. Statutory and Executive Order Reviews

I. Executive Summary

A. What action is the EPA taking?

The EPA is proposing action on the October 8, 2025, submittal by the Arizona Department of Environmental Quality (ADEQ or “State”) of MCAQD Rule 352, “Gasoline Cargo Tank Testing and Use,” as revised on October 1, 2025 (“Rule 352”), and MCAQD Rule 353, “Storage and Loading of Gasoline at a Gasoline Dispensing Facility (GDF),” as revised on October 1, 2025 (“Rule 353”) (collectively, “the MCAQD submittal”). The MCAQD submittal is also intended to meet RACT requirements for the 2008 8-hour ozone NAAQS for the category of sources regulated by each rule.

Rule 352 limits VOC emissions from gasoline cargo tanks that are used to load or unload gasoline within Maricopa County. Because it fulfills all relevant requirements, we are proposing to fully approve Rule 352 and the County's RACT demonstration for the 2008 8-hour ozone NAAQS for the category of sources covered by the EPA Control Techniques Guideline (CTG) document, “Control of Volatile Organic Compound Leaks from Gasoline Tank ( printed page 51636) Trucks and Vapor Collection Systems.” ^[1]

Rule 353 limits VOC emissions from storage and loading of gasoline at gasoline dispensing facilities (GDFs). We are proposing to conditionally approve Rule 353 and the County's RACT demonstration for the 2008 8-hour ozone NAAQS for the category of sources covered by the EPA CTG document “Design Criteria for Stage I Vapor Control Systems—Gasoline Service Stations.” ^[2] We are proposing to conditionally approve Rule 353 and the associated RACT demonstration based on a commitment from the ADEQ to correct a deficiency in Rule 353 within one year of the EPA's final action on the MCAQD submittal. The deficiency relates to the enforceability of a provision that adds a new annual testing requirement but cites to and relies on requirements in an Arizona statute that has not been approved into the Arizona SIP.

If finalized as proposed, Rules 352 and 353 would be incorporated into the federally enforceable portion of the Maricopa County portion of the Arizona SIP and would replace the current SIP-approved versions.

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

We are taking this proposed action under CAA section 110. 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 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 the 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 the MCAQD submittal to be approved we must consider several requirements related to enforceability and stringency of the emission limitations. CAA section 110(a)(2)(A) requires emission limitations in the SIP to be enforceable and 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 have legally enforceable procedures for monitoring the status of compliance with the requirements in the control strategy. Further, this submittal is intended to meet the RACT requirement in CAA section 182(b)(2) for the 2008 8-hour ozone NAAQS. Thus, these rules must also establish RACT level controls for the applicable sources.

Because Rule 353 is not fully approvable, we are proposing to conditionally approve this portion of the MCAQD submittal under CAA section 110(k)(4). Under CAA section 110(k)(4), the EPA may approve a plan revision based on a commitment from the State to adopt specific enforceable measures by not later than one year after the date of approval of the plan revision. Any such conditional approval shall be treated as a disapproval if the State fails to comply with such commitment. On June 9, 2026, the ADEQ submitted a commitment to address this deficiency.

The deficiency in Rule 353 relates to CAA section 110(i), which prohibits the modification of SIP requirements outside the SIP approval process. The rule cites requirements that are not a part of the Arizona SIP and could result in the modification or relaxation of SIP requirements without a SIP revision.

II. Background

Rules 352 and 353 regulate emissions of VOC, which contribute to the formation of ground-level ozone. Ozone harms human health and the environment and is a pollutant for which the EPA has established a NAAQS. Section 110(a) of the CAA requires States to submit plans that provide for implementation, maintenance, and enforcement of the NAAQS. In addition, CAA section 182(b)(2) requires that SIPs for ozone nonattainment areas classified as “Moderate” or higher implement RACT for sources covered by a control techniques guidelines (CTG) document. The MCAQD regulates a portion of the Phoenix-Mesa area designated as nonattainment for ozone and classified as Moderate nonattainment for the 2008 ozone NAAQS.^[3] Therefore, the MCAQD is required to submit SIP revisions that implement RACT-level controls for all sources covered by a CTG. For the 2008 8-hour ozone NAAQS, the MCAQD submitted Rule 352 and Rule 353 to establish RACT-level controls for VOC emissions from sources covered by the CTGs listed in Table 1. Rule 352 limits VOC emissions from gasoline cargo tanks that are used to load or unload gasoline within Maricopa County. Rule 353 limits VOC emissions from storage and loading of gasoline at GDFs.

( printed page 51637)

Section III.D of the preamble to the EPA's final rule to implement the 2008 8-hour ozone NAAQS discusses RACT requirements.^[4] It states in part that RACT SIPs must contain adopted RACT regulations, certifications where appropriate that existing provisions are RACT, and/or negative declarations that there are no sources in the nonattainment areas subject to a specific CTG. The County's RACT SIP provides MCAQD's analysis of its compliance with the CAA section 182 RACT requirements for the 2008 8-hour ozone NAAQS.^[5]

On February 26, 2020, the EPA conditionally approved MCAQD Rule 352, MCAQD Rule 353, and the County's RACT demonstration for the CTGs associated with these rules into the Arizona SIP.^[6] The rules contained deficiencies that precluded full SIP approval and were conditionally approved based on a commitment by the MCAQD and the ADEQ to provide, within one year, a SIP submission that would address those deficiencies. The MCAQD subsequently revised these rules to address the identified deficiencies and ADEQ submitted the revised rules on December 3, 2020. On January 10, 2025, the EPA finalized a limited approval and limited disapproval of MCAQD Rule 352 and Rule 353, and we disapproved the County's RACT demonstration for the CTGs associated with these rules.^[7] The EPA concluded that the State met its commitment and that these revised rules corrected the deficiencies previously identified in the earlier versions of the rules that were conditionally approved into the SIP. However, the rules contained newly identified deficiencies that precluded full SIP approval. Additionally, because of the disapprovals, the CAA requires offset sanctions under the nonattainment New Source Review program to be triggered 18 months after the action's effective date of February 10, 2025, and highway sanctions six months later, unless the State submits revisions that correct the deficiencies. Further, the EPA must promulgate a Federal Implementation Plan (FIP) under CAA section 110(c) unless we approve subsequent SIP revisions that correct the deficiencies within 24 months.

The MCAQD subsequently revised these rules to address the identified deficiencies and ADEQ submitted the revised rules on October 8, 2025. These revised rules are the versions we are proposing to conditionally approve in this proposed action. The EPA's technical support document (TSD) for each rule has more background information on our prior actions related to these rules and is available in the docket for this action.

III. Summary of Arizona's Submittal

On October 8, 2025, the ADEQ, the governor's designee for Arizona SIP submittals, submitted the MCAQD submittal to the EPA on behalf of the MCAQD. The MCAQD submittal includes the rules listed in Table 2 that we are proposing for inclusion in the federally enforceable Arizona SIP. The submittal also includes documents demonstrating that the submittal was adopted in accordance with CAA section 110 and includes the Department's technical support materials. On April 8, 2026, the submittal became complete by operation of law with respect to the completeness criteria in 40 CFR part 51, appendix V.

If Rule 352 is approved and Rule 353 is conditionally approved, these rules would replace the current SIP-approved versions in the Arizona SIP from our January 10, 2025, limited approval and limited disapproval action.^[8] Additionally, the prior disapproval of the County's RACT demonstration for the CTGs associated with these rules would be approved for Rule 352 and conditionally approved for Rule 353.

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 SIP revisions must not interfere with applicable requirements concerning attainment and reasonable further progress or other CAA requirements.^[9] In addition, because these rules were submitted to satisfy the RACT requirement for sources covered by the CTGs listed in Table 1, these rules must establish RACT level controls for such sources. For our evaluation, we considered relevant guidance and policy documents to evaluate enforceability, revision/relaxation, and rule stringency requirements for the applicable criteria pollutants.^[10]

B. Does the submittal meet the evaluation criteria?

The EPA is proposing to conclude that these revised rules have corrected the deficiencies previously identified in our limited approval and limited disapproval action. Below we summarize the prior deficiencies and explain how they have been corrected. The TSD has more information on our evaluation, including in-depth descriptions of the individual deficiencies and the way that each was addressed in the current submitted version of the rules.

1. Prior Deficiencies in Rule 352

In our January 2025 limited disapproval and limited disapproval action, we identified that Rule 352 outlined leak detection tests to be performed beyond the annual certification test, but the rule did not require those tests to be conducted periodically, nor did it establish any requirements for maintaining records or ( printed page 51638) reporting the results.^[11] To address this deficiency, MCAQD clarified that such leak inspections and vapor tightness determinations outside of the annual vapor tightness certification test are for inspections performed by MCAQD and not owners and operators. Additionally, MCAQD added a corrective action schedule for repairing and retesting equipment when a leak is identified from these inspections and added a requirement for the MCAQD to document and maintain records when it performs such tests.^[12] These changes eliminate requirements that depended on specialized training for owners and operators to calibrate testing equipment. These previous requirements lacked a clear enforcement mechanism. Rule 352 now includes enforceable recordkeeping requirements for these tests and because the additional testing is performed by MCAQD; therefore separate reporting by the owner/operator to the County is unnecessary.^[13] In combination with the existing annual vapor tightness certification testing, we can conclude that the compliance provisions of the Rule are sufficient, the Rule is enforceable, and this deficiency has been corrected.

The other Rule 352 deficiency identified in our January 2025 limited approval and limited disapproval action involved procedures for establishing an exemption from the annual vapor tightness testing requirements.^[14] The rule allowed gasoline cargo tank owners and operators to be exempt from the annual testing if they demonstrated compliance through a test method “at least as stringent as” the tests specified in the rule. This language was previously not enforceable because it did not specify which alternative test methods are acceptable to qualify for the exemption or who would determine whether the alternative test methods met the required level of stringency. This ambiguity could have allowed changes to testing requirements without following the CAA's required SIP revision process. To address this deficiency MCAQD removed the phrase “at least as stringent as those,” therefore requiring gasoline cargo tank testing companies to use only the test methods specified in the rule to demonstrate vapor tightness.^[15]

2. Prior Deficiencies in Rule 353

In our January 2025 limited approval and limited disapproval action,^[16] we identified that Rule 353 did not require all sources subject to the rule's vapor tight standard to conduct periodic testing to demonstrate compliance. The rule included a weekly monitoring requirement, but that requirement did not ensure the use of a replicable test method for demonstrating vapor tightness. Rule 353 required a facility to first determine if there is a “potential vapor leak” prior to being required to determine the vapor tight status using applicable test methods. The rule allowed owners and operators to choose from a menu of monitoring options with one option being “sight, sound, or smell.” ^[17] We explained that while the use of sight, sound, or smell allows for a high frequency of relatively simple checks, allowing the use of sight, sound, or smell to potentially be the only mechanism used in determining a potential vapor leak would allow for the vapor tight status of equipment to be solely evaluated based on the operator's discretion and sensory inputs. To address this deficiency, MCAQD added a requirement for annual testing of Stage I vapor recovery systems that handle 10,000 gallons or more of gasoline in a month, with testing performed by a licensed Arizona Department of Agriculture, Weights and Measures Services Division service representative. Although the rule does not specify the testing methods, existing Arizona SIP requirements already require annual testing using California Air Resources Board (CARB) TP-201.4, CARB TP-201.5, and San Diego TP-96-1.^[18] Therefore, the identified deficiency is considered resolved.

In our January 2025 limited approval and limited disapproval action we identified that Rule 353 contained reporting requirements that applied to some but not all sources subject to Rule 353. While Rule 353 requires reporting of some compliance information for most sources, it did not include such a requirement for aviation gasoline.^[19] To correct this deficiency, MCAQD added a requirement to Rule 353 that ensures storage tanks with aviation gasoline must meet the same reporting requirements.^[20]

3. New Deficiency in Rule 353

Rule 353 now requires annual testing “in accordance with Arizona Revised Statutes [A.R.S.] § 3-3512(C)(5).” ^[21] However, A.R.S. section 3-3512(C)(5) is not in the Arizona SIP and has not been submitted for SIP approval. CAA section 110(a)(2)(A) requires emission limits to be enforceable, and 40 CFR 51.212 requires SIPs to provide for periodic testing of stationary sources and the use of enforceable test methods for each emission limitation. Reliance on requirements outside of the Arizona SIP could allow the SIP requirements to be revised and relaxed without the CAA section 110(i) required SIP approval process. Further, submittal of A.R.S. section 3-3512 alone would be insufficient since the SIP would still not otherwise specify which tests are needed to comply with Rule 353. As a result, EPA is proposing to determine that this undermines the enforceability of the submission and is inconsistent with the requirements of CAA Section 110.

On June 9, 2026, ADEQ submitted a commitment to the EPA to submit the State's current version of its vapor recovery statutes and regulations for EPA approval into the SIP within one year of the EPA's final action on the MCAQD submittal.^[22] The inclusion of these provisions in the SIP, which include A.R.S. section 3-3512(C)(5) and specific testing requirements with test methods, would ensure that the necessary test methods are clearly specified within the SIP and would resolve the identified deficiency.

Based on our evaluation, and as described in more detail in the TSDs in the docket for this action, the submitted ( printed page 51639) rules resolve the previously identified deficiencies, strengthen the SIP, and generally establish RACT level controls. However, EPA is proposing to conditionally approve Rule 353 because the ADEQ has committed to correcting a new deficiency that prevents full approval of the rule.

C. The EPA's Recommendations

The TSDs include additional recommendations for MCAQD related to these rules.

D. Proposed Action and Public Comment

As authorized in section 110(k)(3) of the Act, the EPA proposes to fully approve Rule 352 and the RACT demonstration for the source category associated with the rule in Table 1 for the 2008 8-hour ozone NAAQS standard because it fulfills all relevant requirements. If we finalize this approval as proposed, we will replace the current SIP-approved version with the October 8, 2025 submitted version in the federally enforceable SIP and stop all sanctions clock and the Federal Implementation Plan (FIP) obligations associated with our January 10, 2025, limited disapproval of Rule 352 and the associated CTG RACT obligation.

As described in section IV.B of this preamble, our analysis indicates that Rule 353 largely fulfills the relevant CAA section 110 and part D requirements, but the identified deficiency precludes full SIP approval pursuant to section 110(k)(3) of the Act. Section 110(k)(4) of the CAA authorizes the EPA to conditionally approve SIP revisions based on a commitment by the state to adopt specific enforceable measures by a date certain but not later than one year after the date of the plan approval.^[23] Because ADEQ has committed to provide the EPA with a SIP submission within one year of final action of Rule 353 that will include updated rules that would adequately address the identified deficiency, we are proposing to conditionally approve Rule 353 pursuant to section 110(k)(4) of the Act. If ADEQ submits the updated rules by the specified deadline, and the EPA approves the submission, then the identified deficiency will be cured. However, if this proposed conditional approval is finalized and ADEQ fails to submit the revision within the required timeframe, the conditional approval will be treated as a disapproval. In addition, as authorized in section 110(k)(3) of the Act, the EPA is proposing a conditional approval of the RACT demonstration for the 2008 ozone NAAQS for the sources covered by the CTG associated with Rule 353, because the deficiency precludes the EPA from proposing to approve this RACT demonstration as a whole. If we finalize this conditional approval as proposed, we will replace the current SIP-approved version with the October 8, 2025, submitted version in the federally enforceable SIP and stop all sanctions clock and the FIP obligations associated with our January 10, 2025, limited disapproval of Rule 353 and the associated CTG RACT obligation. We are concurrently making an interim final determination to stay and defer the CAA section 179 sanctions associated with our January 10, 2025 limited disapproval of Rule 352 and Rule 353. Consistent with our order of sanction regulations,^[24] this determination is based on this proposed approval of SIP revisions to resolve the deficiencies that were the basis of our prior January 10, 2025 limited disapproval.

We will accept comments from the public on this proposal until September 10, 2026. If we take final action to approve and conditionally approve the submitted rules, our final action will incorporate these rules into the federally enforceable SIP.

III. Incorporation by Reference

In this proposed rule, 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 MCAQD Rule 352, “Gasoline Cargo Tank Testing and Use,” revised on October 1, 2025, which regulates VOC emissions during loading and unloading of gasoline to any gasoline cargo tank within Maricopa County. The EPA is also proposing to incorporate by reference MCAQD Rule 353, “Storage and Loading of Gasoline at a Gasoline Dispensing Facility (GDF),” revised on October 1, 2025, which regulates VOC emissions during storage and loading of gasoline at gasoline dispensing facilities. 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).

IV. 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 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 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 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 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).

91 FR 51635