Data / Federal rules / 2025-17499
Air Plan Approval; Montana; Regional Haze Plan for the Second Implementation Period; Prong 4 (Visibility) for the 2015 8-Hour Ozone National Ambient Air Quality Standard
The Environmental Protection Agency published this proposed rule in the Federal Register on September 11, 2025. Comments closed on October 14, 2025.
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What the agency says
The Environmental Protection Agency (EPA) is proposing to approve the regional haze state implementation plan (SIP) submission submitted by the State of Montana on August 10, 2022, under the Clean Air Act (CAA) and the EPA's Regional Haze Rule (RHR) for the program's second implementation period. Montana's 2022 SIP submission addresses the requirement that states revise their long-term strategies every implementation period to make reasonable progress towards the national goal of preventing any future, and remedying any existing, anthropogenic impairment of visibility, including regional haze, in mandatory Class I Federal areas. Montana's 2022 SIP submission also addresses other applicable requirements for the second implementation period of the regional haze program. The EPA is also proposing to approve the prong 4 visibility portion of Montana's October 1, 2018 Infrastructure SIP submission for the 2015 ozone National Ambient Air Quality Standards (NAAQS). The EPA is taking these actions pursuant to the CAA.
Key facts
- Document number
- 2025-17499
- Type
- Proposed rule
- Action
- Proposed rule
- Agency
- Environmental Protection Agency
- Published
- September 11, 2025
- Comments due
- October 14, 2025
- Dates
- Written comments must be received on or before October 14, 2025.
- Docket
- EPA-R08-OAR-2024-0608; FRL-12597-01-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
- 14
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