SUPPLEMENTARY INFORMATION:

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

Table of Contents

I. What is being addressed in this document?

II. Background

III. Public Comments and EPA Responses

IV. Final Action

V. Statutory and Executive Order Reviews

I. What is being addressed in this document?

The EPA is approving a SIP revision submitted by the State of Montana to the EPA on August 10, 2022, addressing the requirements of the second implementation period of the RHR. As required by section 169A of the CAA, the RHR calls for state and federal agencies to work together to improve visibility in 156 national parks and wilderness areas. The rule requires the states, in coordination with the EPA, the National Park Service, Fish and Wildlife Service, the Forest Service, and other interested parties, to develop and implement air quality protection plans to reduce the pollution that causes visibility impairment in mandatory Class I Federal areas. Visibility impairing pollutants include fine and coarse particulate matter (PM) ( e.g., sulfates, nitrates, organic carbon, elemental carbon, and soil dust) and their precursors ( e.g., sulfur dioxide (SO₂), oxides of nitrogen (NO_X), and, in some cases, volatile organic compounds (VOC) and ammonia (NH₃)). As discussed in further detail in our proposed rule, this document, and the accompanying Response to Comments ( printed page 54587) (RTC) document, the EPA finds that Montana submitted a regional haze SIP that meets all the regional haze requirements for the second implementation period. The State's submission, the proposed rule, and the RTC document can be found in the docket for this action.

II. Background

On August 10, 2022, Montana submitted a revision to its SIP to address its regional haze obligations for the second implementation period (2018-2028). Montana made this revision to satisfy the requirements of the CAA's regional haze program pursuant to CAA sections 169A and 169B and 40 Code of Federal Regulations (CFR) 51.308.

On September 11, 2025, the EPA proposed to approve Montana's 2022 SIP submission.^[1] Specifically, the EPA proposed to approve Montana's 2022 SIP submission as satisfying the requirements of 40 CFR 51.308(f)(1): calculations of baseline, current, and natural visibility conditions, progress to date, and the uniform rate of progress; 40 CFR 51.308(f)(2): long-term strategy; 40 CFR 51.308(f)(3): reasonable progress goals; 40 CFR 51.308(f)(4): reasonably attributable visibility impairment; 40 CFR 51.308(f)(5) and 40 CFR 51.308(g): progress report requirements; 40 CFR 51.308(f)(6): monitoring strategy and other implementation plan requirements; and 40 CFR 51.308(i): Federal Land Manager (FLM) consultation. Our public comment period closed on October 14, 2025.

The September 11, 2025, proposed rule provided background on the requirements of the CAA and RHR, a summary of Montana's regional haze SIP submittal and related EPA actions, and the EPA's rationale for its proposed action. That background and rationale will not be restated here. For the reasons stated in the proposed rule, this document, and in the accompanying RTC document, the EPA concludes that Montana's 2022 SIP submission meets the requirements of the CAA and RHR.

III. Public Comments and EPA Responses

The public comment period on the proposal closed on October 14, 2025. During the public comment period, we received 16 comments on our proposal: 1 in support and 15 in opposition. The commenters were: Conservation Groups,^[2] the Mid-Atlantic/Northeast Visibility Union (MANEVU),^[3] Cabinet Resource Group,^[4] Talen Montana,^[5] and eight individual commenters.^[6] The full text of comments received is included in the publicly posted docket associated with this action at https://www.regulations.gov. Our RTC document, which is also included in the docket associated with this action, provides detailed responses to all significant comments received.

IV. Final Action

For the reasons stated in the preamble to the proposed rule, in the RTC document, and in this document, we are approving Montana's 2022 SIP submission. Specifically, we are approving Montana's 2022 SIP submission relating to CAA 169A:

• Calculations of baseline, current, and natural visibility conditions, progress to date, and uniform rate of progress (40 CFR 51.308(f)(1));
• Long-term strategy (40 CFR 51.308(f)(2));
• Reasonable progress goals (40 CFR 51.308(f)(3));
• Reasonably attributable visibility impairment (40 CFR 51.308(f)(4));
• Progress report requirements (40 CFR 51.308(f)(5) and 40 CFR 51.308(g));
• Monitoring strategy and other implementation plan requirements (40 CFR 51.308(f)(6));
• FLM consultation (40 CFR 51.308(i)).

In addition, we are approving the prong 4 visibility portion of Montana's October 1, 2018 Infrastructure SIP submission for the 2015 ozone NAAQS.

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 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 action:

• Is not a “significant regulatory action” subject to review by the Office of Management and Budget under Executive Orders 12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
• Is not subject toExecutive Order 14192 (90 FR 9065, February 6, 2025) because State Implementation Plan approvals under the CAA 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, 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);
• 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 27, 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)).

For the reasons stated in the preamble, the Environmental Protection Agency is amending 40 CFR part 52 as follows:

90 FR 54586