Data / Federal rules / 2025-21340

Air Plan Approval; Montana; Regional Haze Plan for the Second Implementation Period

The Environmental Protection Agency published this final rule in the Federal Register on November 28, 2025. It took effect on December 29, 2025.

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What the agency says

The Environmental Protection Agency (EPA) is approving a regional haze state implementation plan (SIP) revision submitted by the State of Montana on August 10, 2022 (Montana's 2022 SIP submission), as satisfying applicable requirements under the Clean Air Act (CAA) and the EPA's Regional Haze Rule (RHR) for the program's second implementation period. The EPA is also finalizing approval of the prong 4 visibility portion of Montana's October 1, 2018, Infrastructure SIP submission for the 2015 ozone National Ambient Air Quality Standard (NAAQS). The EPA is taking this action pursuant to the CAA.

Key facts

Document number: 2025-21340
Type: Final rule
Action: Final rule
Agency: Environmental Protection Agency
Published: November 28, 2025
Takes effect: December 29, 2025
Dates: This rule is effective on December 29, 2025.
Docket: EPA-R08-OAR-2024-0608; FRL-12597-02-R8
Code of Federal Regulations: 40 CFR 52
Topics: Air pollution control; Carbon monoxide; Environmental protection; Greenhouse gases; Incorporation by reference; Intergovernmental relations; Lead; Nitrogen dioxide; Ozone; Particulate matter; Reporting and recordkeeping requirements; Sulfur oxides; Volatile organic compounds
Pages: 3

The document on federalregister.gov PDF

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Everything from the Environmental Protection Agency · Rules on air pollution control · Rules on carbon monoxide · Rules on environmental protection · Published in November 2025

Read from the Federal Register API, last updated 2026-10-23. The document on federalregister.gov is the official record; dates and dockets can change through later corrections. Free to reuse with credit to SpecStream under CC BY 4.0.