# Air Plan Revisions; Arizona; Maricopa County Air Quality Department; Volatile Organic Compounds; Solvent Cleaning
**AGENCY:**
Environmental Protection Agency (EPA).
**ACTION:**
Proposed rule.
**SUMMARY:**
The Environmental Protection Agency (EPA) is proposing to approve revisions to the Maricopa County Air Quality Department (MCAQD) portion of the Arizona State Implementation Plan (SIP). These revisions concern rules that regulate volatile organic compounds (VOC) emissions from solvent cleaning operations. We are proposing to approve the revisions under the Clean Air Act (CAA or “Act”). We are taking comments on this proposal and plan to follow with a final action.
**DATES:**
Comments must be received on or before October 14, 2025.
**ADDRESSES:**
Submit your comments, identified by Docket ID No. EPA-R09-OAR-2025-0321 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:**
Allison Kawasaki, EPA Region IX, 75 Hawthorne St., San Francisco, CA 94105; telephone number: (415) 972-3922; email address: *[email protected].*
**SUPPLEMENTARY INFORMATION:**
Throughout this document, “we,” “us,” and “our” refer to the EPA.
**Table of Contents**
I. The State's Submittal
A. What did the State submit?
B. Are there other related submittals?
C. What is the purpose of the submittal?
II. The EPA's Evaluation and Action
A. How is the EPA evaluating the rule and the request for rescission and replacement?
B. Do the SIP revisions meet the evaluation criteria?
C. Proposed Action and Public Comment
III. Incorporation by Reference
IV. Statutory and Executive Order Reviews
**I. The State's Submittal**
**A. What did the State submit?**
On October 3, 2024, the Arizona Department of Environmental Quality (ADEQ) submitted a SIP revision to the EPA from MCAQD requesting that the EPA approve MCAQD Rule 331—Solvent Cleaning (“Rule 331”), as revised on September 25, 2024 (“2024 SIP Submittal”). Additionally, the 2024 SIP Submittal requests that we rescind two sets of requirements from the SIP: MCAQD Rule 331, as revised on April 21, 2004, and paragraphs F, G, H, I, J, and K of Rule 34—Organic Solvents—Volatile Organic Compounds (VOC) (“Rule 34”), as revised on June 23, 1980.
Table 1 lists the rule we are proposing for approval with the dates that it was adopted by the local air agency and submitted to the EPA by the ADEQ. Table 2 lists the rules proposed to be rescinded from the SIP with the dates that they were adopted by the local air agency and approved into the SIP.
| Local | Rule No. | Rule title | Revised | Submitted |
| --- | --- | --- | --- | --- |
| MCAQD | 331 | Solvent Cleaning | September 25, 2024 | October 3, 2024. |
| Local | Rule No. | Rule title | Local revision date | SIP approved date | FR citation |
| --- | --- | --- | --- | --- | --- |
| MCAQD | 34—paragraphs F, G, H, I, J, and K | Organic Solvents—Volatile Organic Compounds (VOC) | June 23, 1980 | May 5, 1982 | 47 FR 19326. |
| MCAQD | 331 | Solvent Cleaning | April 21, 2004 | December 21, 2004 | 69 FR 76417. |
On April 3, 2025, the 2024 SIP Submittal was deemed by operation of law to be complete. We have reviewed the submittal to ensure it meets the completeness criteria in 40 CFR part 51, appendix V.
**B. Are there other related submittals?**
In 2016, the EPA reformatted the Arizona SIP as codified in the Code of Federal Regulations (CFR) into a tabulated “notebook” format. While developing the updated SIP tables for that conversion, the EPA worked closely with ADEQ and the local air agencies to clarify what was in their applicable SIP, including older provisions that had not been updated or replaced to reflect local rulemakings. On September 13, 2017, because of that coordination, the ADEQ submitted a SIP revision from MCAQD that requested to rescind or replace many obsolete rules in their federally enforceable SIP in favor of rules that reflect their current locally enforceable rulebook (“2017 SIP submittal”).
The 2017 SIP Submittal included requests related to Rule 34, MCAQD Rule 330—Volatile Organic Compounds (“Rule 330”), and Rule 331. The submittal requested that paragraphs F, G, H, I, J, and K of Rule 34 [^1] be replaced in the SIP by approval of Rule 330, as adopted on September 25, 2013. The submittal also requested that the EPA remove SIP-approved Rule 331 [^2] and replace it in the SIP with Rule 331, as revised on September 24, 2013. As clarified by MCAQD in the 2024 SIP Submittal, these requests have been superseded by the 2024 SIP Submittal. Although these requests have been superseded, this action is a part of this ongoing effort.
[^1] Approved into the SIP on May 5, 1982 (47 FR 19326).
[^2] Approved into the SIP on December 21, 2004 (69 FR 76417).
If we finalize this rulemaking as proposed, Rule 331, as revised on September 25, 2024, would replace Rule 34—paragraphs F, G, H, I, J, and K and Rule 331, as revised on April 21, 2004, in the Maricopa County portion of the Arizona SIP.
**C. What is the purpose of the submittal?**
Under title I of the CAA, the EPA has established ambient air quality standards for six common air pollutants (“criteria pollutants”) known to be harmful to human health and the environment: carbon monoxide (CO), lead (Pb), nitrogen dioxide (NO <sub>2</sub> ), ozone, particulate matter (PM), and sulfur dioxide (SO <sub>2</sub> ). These standards are known as the National Ambient Air Quality Standards (NAAQS).
Section 110(a) of the CAA requires states to submit SIP requirements for the attainment and maintenance of the NAAQS. Rules 34 and Rule 331 regulate emissions of VOC from solvent cleaning operations, including metal degreasing. Emissions of VOC contribute to the production of ground-level ozone and PM. Cleaning solvents are used to remove contaminants such as adhesives, inks, paint, dirt, soil, oil, and grease from parts, products, tools, machinery, equipment, vessels, floors, walls, and other work production related work areas. These operations take place for a variety of reasons, including safety, operability, and to avoid product contamination.
Additionally, MCAQD submitted revised Rule 331 to meet CAA reasonably available control technology (RACT) requirements. CAA sections 182(b)(2) and (f) require RACT for each category of sources covered by a Control Techniques Guidelines (CTG) document as well as each major source of VOC or oxides of nitrogen (NO <sub>X</sub> ) in ozone nonattainment areas classified as “Moderate” or above. MCAQD regulates air quality in the Maricopa County portion of the Phoenix-Mesa ozone nonattainment area, which is classified as “Moderate” for the 2008 and 2015 8-hour ozone standards. [^3] Rule 331 regulates categories of sources covered by CTG documents related to solvents. For the 2008 8-hour ozone standard, MCAQD relied on Rule 331, as revised on April 21, 2004, to meet RACT requirements for certain CTG categories. MCAQD revised Rule 331 to meet RACT requirements for the 2015 8-hour ozone standard. The EPA will evaluate Rule 331 for RACT purposes when we review MCAQD's evaluation in their RACT SIP for the 2015 8-hour ozone standard in a separate, future action.
[^3] 40 CFR 81.303; 87 FR 60897 (October 7, 2022); and 81 FR 26697 (May 4, 2016).
MCAQD does not rely on Rule 34 to meet RACT requirements. MCAQD is requesting the rescission of the remaining portions of Rule 34 [^4] in the SIP as part of the ongoing effort to update the Maricopa County portion of the Arizona SIP.
[^4] On September 1, 2022 (87 FR 53676), in a direct final rule, we clarified that paragraphs F, G, H, I, J and K of Rule 34 remain in the Maricopa County portion of the SIP and that paragraphs A, B, C, D, E, and L were rescinded or superseded by prior EPA actions.
A technical support documents (TSD) was prepared for each rule, Rule 34 and 331. The TSDs have more information about the rules.
**II. The EPA's Evaluation and Action**
**A. How is the EPA evaluating the rule and the request for rescission and replacement?**
Emissions limitations in the SIP must be enforceable (see CAA section 110(a)(2)) and must not interfere with applicable requirements concerning attainment and reasonable further progress or other CAA requirements (see CAA section 110(l)). Once a rule has been approved as part of a SIP, the rescission of that rule from the SIP constitutes a SIP revision. To approve such a revision, the change must comply with restrictions on relaxation of SIP measures under CAA sections 110(l) and 193. CAA section 193 requires control requirements in effect in nonattainment areas prior to November 15, 1990, to remain in effect unless the modification ensures equivalent or greater emissions reductions.
Guidance and policy documents that we use to evaluate enforceability and revision/relaxation requirements for the applicable criteria pollutants include the following:
1.“Issues Relating to VOC Regulation Cutpoints, Deficiencies, and Deviations,” EPA, May 25, 1988 (the Bluebook, revised January 11, 1990).
2. “Guidance Document for Correcting Common VOC & Other Rule Deficiencies,” EPA Region 9, August 21, 2001 (the Little Bluebook).
**B. Do the SIP revisions meet the evaluation criteria?**
Rule 331 establishes general work practices to minimize VOC emissions for all solvent cleaning machines and for the handling of cleaning solvents. For vapor and non-vapor cleaning machines, [^5] operators must meet additional solvent specifications, work practices, control requirements, and/or design standards that limit VOC emissions based on the type of cleaning machine utilized. Operators can also choose to use an add-on emissions control system in lieu of the requirements for cleaning machines if it meets an overall capture and control efficiency of 85 percent. Additionally, using a “Low VOC Cleaner” can justify exemption from many requirements in the rule, especially for non-vapor cleaning machines.
[^5] “Vapor” cleaning is when solvent vapor from boiling cleaning solvent is used for cleaning and “non-vapor” cleaning is when liquid solvent is used to clean at temperatures below the solvent boiling point.
Compared to the current SIP-approved version of Rule 331, the most significant change was to revise the definition of “Low VOC Cleaner” from 50 grams per liter (g/L) to 25 g/L. This encourages operators to switch to a lower emitting solvent to avoid the more substantive requirements in the rule. Other revisions improve the overall clarity and enforceability of the rule, such as providing clearer requirements for emissions control systems, adding a compliance schedule section, clarifying definitions, and clarifying monitoring, testing, and recordkeeping requirements.
Rule 331, as revised on September 25, 2024, would strengthen the SIP by establishing a more stringent emissions limitation for Low VOC Cleaners and by clarifying monitoring and recordkeeping provisions. This rule meets the relevant CAA requirements in section 110 and is consistent with relevant guidance regarding enforceability and SIP revisions.
Additionally, we are proposing that the requirements in Rule 331 can be used to replace Rule 34, paragraphs F, G, H, I, J, and K, in the SIP. The requirements in Rule 34 would be replaced with requirements in Rule 331 that are at least as stringent. For example, Rule 331 provides updated terminology, more stringent standards ( *e.g.,* operational and equipment standards, and work practices) and clarity on monitoring and testing requirements.
Based on our evaluation, the replacement of Rule 34 with Rule 331, as revised on September 25, 2024, would not impact the overall stringency of the Arizona SIP and complies with CAA sections 110(l) and 193.
Our two TSDs have more information on our evaluations.
**C. Proposed Action and Public Comment**
As authorized in section 110(k)(3) of the Act, the EPA proposes to approve Rule 331, as revised on September 25, 2024, because it fulfills all relevant CAA requirements. It would replace the current version of Rule 331 in the SIP. The EPA also proposes to approve the requested rescission of Rule 34, sections F, G, H, I, J, and K, by replacing it with Rule 331, as revised on September 25, 2024, because it fulfills all relevant CAA requirements. We will accept comments from the public on this proposal until October 14, 2025. If we take final action to approve Rule 331, our final action will incorporate this rule into the federally enforceable SIP.
**III. 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 Maricopa County Air Quality District, Rule 331, Solvent Cleaning, revised September 25, 2024, which regulates emissions of VOC from solvent cleaning operations. In addition, the EPA is proposing to rescind Rule 34, sections F, G, H, I, J, and K, and replace it with the submitted Rule 331 in the MCAQD portion of the Arizona SIP, because the requested replacement fulfills all relevant requirements. The EPA has made, and will continue to make, these materials available through *https://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 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 oxides, Ozone, Reporting and recordkeeping requirements, Volatile organic compounds.
**Authority:**
42 U.S.C. 7401 *et seq.*
Dated: September 3, 2025.
Michael Martucci,
Acting Regional Administrator, Region IX.