# Section 110(a)(2) infrastructure requirements.
**AGENCY:**
Environmental Protection Agency (EPA).
**ACTION:**
Final rule.
**SUMMARY:**
The Environmental Protection Agency (EPA) is approving elements of a state implementation plan (SIP) submission from Montana regarding the infrastructure requirements of the Clean Air Act (CAA) for the 2015 8-hour ozone National Ambient Air Quality Standards (NAAQS). The infrastructure requirements are designed to ensure that the structural components of each state's air quality management program are adequate to meet the state's responsibilities under the CAA. Additionally, EPA is finalizing approval of Montana's request to update their SIP to incorporate the most recent version of EPA's “Guidelines on Air Quality Models.” EPA is taking this action pursuant to the CAA.
**DATES:**
This rule is effective on December 18, 2025.
**ADDRESSES:**
EPA has established a docket for this action under Docket ID No. EPA-R08-OAR-2019-0418. All documents in the docket are listed on the *https://www.regulations.gov* website. Although listed in the index, some information is not publicly available, *e.g.,* Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy form. Publicly available docket materials are available through *https://www.regulations.gov,* or please contact the person identified in the *FOR FURTHER INFORMATION CONTACT* section for additional availability information.
**FOR FURTHER INFORMATION CONTACT:**
Amrita Singh, Air and Radiation Division, EPA, Region 8, Mailcode 8ARD-IO, 1595 Wynkoop Street, Denver, Colorado 80202-1129, telephone number: (303) 312-6103, email address: *[email protected].*
**SUPPLEMENTARY INFORMATION:**
Throughout this document “we,” “us,” and “our” means EPA.
**I. Background**
Under sections 110(a)(1) and (2) of the CAA, each state is required to submit a SIP that provides for the implementation, maintenance, and enforcement of a revised primary or secondary NAAQS or standard. CAA sections 110(a)(1) and (2) requires each state to make a new SIP submission within three years after EPA promulgates a new or revised NAAQS for approval into the existing federally approved SIP to assure that the SIP meets the applicable requirements for new and revised NAAQS.
On July 16, 2025 EPA proposed to approve all elements of a SIP submission from the Montana Department of Environmental Quality (MDEQ) submitted on October 1, 2018 except for those previously approved in 87 FR 21578. We proposed approval for the following CAA section 110(a)(2) infrastructure elements for the 2015 ozone NAAQS: (A), (B), (C), (D)(i)(II), (D)(ii), (E), (F), (G), (H), (J), (K), (L) and (M). Concurrently, EPA also proposed to approve revisions to appendix W submitted on December 28, 2022. An explanation of the CAA requirements, detailed analysis of the revisions, and EPA's reasons for proposing approval were provided in the proposed rulemaking (90 FR 31911).
**II. Response to Comments**
During the public comment period of EPA's July 16, 2025, proposed rulemaking, EPA received one anonymous comment in support of our action and one anonymous adverse comment. A summary of the comments and EPA's response are provided below.
*Comment:* The commentor urged EPA to consider the role of CO <sub>2</sub> emissions and climate change in ozone formation when reviewing the Montana infrastructure SIP for the 2015 ozone NAAQS. The commentor stated that climate-change driven factors such as increased temperatures, biogenic emissions, and wildfire activity is projected to influence both the frequency and severity of ozone exceedances and suggested that infrastructure SIPs should acknowledge the long-term planning risks associated with climate-driven ozone trends.
*Response:* EPA appreciates the commenter's concern regarding the influence of CO <sub>2</sub> emissions and climate change on ozone formation and air quality. However, the scope of this action is limited to determining whether Montana's SIP meets the infrastructure requirements of CAA section 110(a)(1) and (2) for the 2015 ozone NAAQS. These requirements address the basic structural elements of a state's air quality management program. EPA's review of Montana's SIP submission is limited to the applicable statutory and regulatory requirements for infrastructure SIPs related to the 2015 ozone NAAQS, which the submission satisfies. Therefore, the considerations raised by the commentor are outside the scope of this rulemaking.
*Comment:* The commentor supported EPA's proposal to approve Montana's infrastructure SIP submission for the 2015 ozone NAAQS, noting that Montana has met the CAA's structural requirements. The commentor encouraged EPA and the Montana Department of Environmental Quality to ensure strong public education, transparency, and community outreach efforts.
*Response:* EPA appreciates the commentor's support for this action. The scope of this action is limited to evaluating whether Montana's SIP submission meets the infrastructure requirements of the CAA section 110(a)(1) and (2) for the 2015 Ozone NAAQS. EPA has determined that Montana's SIP submission satisfies the applicable statutory and regulatory requirements for this action.
**III. Final Action**
EPA is approving the infrastructure SIP elements listed in table 1 below. These elements were included in a SIP submission from Montana certifying that its current SIP is sufficient to meet the required elements under section 110(a)(1) and (2) for the 2015 ozone NAAQS. Additionally, EPA is approving the revisions to appendix W submitted by the State of Montana on December 28, 2022.
| Elements | Approval status |
| --- | --- |
| (A): Emission Limitations and Other Control Measures | Approve. |
| (B): Ambient Air Quality Monitoring/Data System | Approve. |
| (C): Program for Enforcement of Control Measures; minor NSR; PSD | Approve. |
| (D)(i)(I): Prong 1 Interstate Transport—significant contribution | Previously approved in 87 FR 21578. |
| (D)(i)(I): Prong 2 Interstate Transport—interference with maintenance | Previously approved in 87 FR 21578. |
| (D)(i)(II): Prong 3 Interstate Transport—PSD | Approve. |
| (D)(i)(II): Prong 4 Interstate Transport—visibility | Previously approved in 87 FR 21578. |
| (D)(ii): Interstate and International Pollution Abatement | Approve. |
| (E): Adequate Personnel. Funding, and Authority; State Boards; Local Implementation | Approve. |
| (F): Stationary Source Monitoring | Approve. |
| (G): Emergency Authority; Emergency Episode Plans | Approve. |
| (H): Future SIP Revisions | Approve. |
| (J): Consultation with Government Officials, Public Notification, PSD and Visibility Protection | Approve. |
| (K): Air Quality Modeling/Data | Approve. |
| (L): Permitting Fees | Approve. |
| (M): Consultation/Participation by Affected Local Entities | Approve. |
**IV. Incorporation by Reference**
In this document, EPA is finalizing regulatory text that includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, EPA is finalizing the incorporation by reference of appendix W revisions submitted by the State of Montana as discussed in the previously mentioned proposed rulemaking that can be found in the *Federal Register* at 90 FR 31911. EPA has made, and will continue to make, these materials generally available through *https://www.regulations.gov* and at the EPA Region 8 Office (please contact the person identified in the *FOR FURTHER INFORMATION CONTACT* section of this preamble for more information).
**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 CAA and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to approve state choices, provided that they meet the criteria of the CAA. Accordingly, this action merely approves 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 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 approves 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 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).
This action is subject to the Congressional Review Act (CRA), and EPA will submit a rule report to each House of the Congress and to the Comptroller General of the United States. This action is not a “major rule” as defined by 5 U.S.C. 804(2).
Under section 307(b)(1) of the CAA, petitions for judicial review of this action must be filed in the United States Court of Appeals for the appropriate circuit by January 20, 2026. Filing a petition for reconsideration by the Administrator of this final rule does not affect the finality of this action for the purposes of judicial review nor does it extend the time within which a petition for judicial review may be filed, and shall not postpone the effectiveness of such rule or action. This action may not be challenged later in proceedings to enforce its requirements (see section 307(b)(2)).
**List of Subjects in 40 CFR Part 52**
Environmental protection, Air pollution control, Carbon monoxide, Incorporation by reference, Intergovernmental relations, Lead, Nitrogen dioxide, Ozone, Particulate matter, Reporting and recordkeeping requirements, Sulfur oxides, Volatile organic compounds.
Dated: October 29, 2025.
Cyrus M. Western,
Regional Administrator, Region 8.
For the reasons set forth in the preamble, the Environmental Protection Agency is amending 40 CFR part 52 as follows:
**PART 52—APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS**
**40 CFR Part 52**
1. The authority citation for part 52 continues to read as follows:
**Authority:**
42 U.S.C. 7401 *et seq.*
**Subpart BB—Montana**
**40 CFR Part 52**
2. In § 52.1370:
a. The table in paragraph (c) is amended by revising the entry “17.8.802”.
b. The table in paragraph (e) is amended by adding the entry “Infrastructure Requirements for the 2015 8-hour Ozone National Ambient Air Quality Standards” under the heading entitled “(1) Statewide” at the end of the section.
The revision and addition read as follows:
§ 52.1370
(c) * * *
| State citation | Rule title | State effective date | EPA final rule date | Final rule citation | Comments |
| --- | --- | --- | --- | --- | --- |
| | | | | | |
| | | | | | |
| * * * * * * * | | | | | |
| 17.8.802 | Incorporation By Reference | 5/13/2022 | 11/18/2025 | 90 FR [insert
page where the document begins] | Excluding (1)(c)-(d). |
| | | | | | |
| * * * * * * * | | | | | |
(e) * * *
| Title/subject | State effective date | Notice of final rule date | NFR citation |
| --- | --- | --- | --- |
| | | | |
| | | | |
| * * * * * * * | | | |
| Infrastructure Requirements for the 2015 8-hour Ozone National Ambient Air Quality Standards | N/A | 11/18/2025 | 90 FR [insert
page where the document begins]. |
| | | | |
| * * * * * * * | | | |
**40 CFR Part 52**
3. In § 52.1394, add paragraph (c) to read as follows:
§ 52.1394
(c) On September 26, 2018, Steve Bullock, Governor, State of Montana, submitted a certification letter which provides the State of Montana's SIP provisions which meet the requirements of CAA section 110(a)(1) and (2) relevant to the 2015 8-hour Ozone NAAQS.