Data / Federal rules / 2025-19714

Determination of Attainment by the Attainment Date; California; Mariposa County; 2015 8-Hour Ozone National Ambient Air Quality Standards

The Environmental Protection Agency published this final rule in the Federal Register on October 30, 2025. It took effect on December 1, 2025.

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What the agency says

The Environmental Protection Agency (EPA) is taking final action to determine that the Mariposa County nonattainment area in California ("Mariposa area") attained the 2015 ozone national ambient air quality standards (NAAQS or "standard") by its August 3, 2024 attainment date. Our determination of attainment is based on complete, quality-assured, and certified ambient air quality monitoring data for calendar years 2021-2023, excluding data that showed exceedances due to exceptional events that occurred in 2021 and 2022. As a result of this action, Clean Air Act (CAA or "Act") section 172(c)(9) contingency measures for failure to attain the 2015 ozone NAAQS and contingency measures for failure to make reasonable further progress (RFP) are no longer required for this standard in the Mariposa area. This action fulfills the EPA's statutory obligation to determine whether the Mariposa area attained the NAAQS by the attainment date.

Key facts

Document number: 2025-19714
Type: Final rule
Action: Final rule
Agency: Environmental Protection Agency
Published: October 30, 2025
Takes effect: December 1, 2025
Dates: This rule is effective on December 1, 2025.
Docket: EPA-R09-OAR-2025-0084; FRL-12611-02-R9
Code of Federal Regulations: 40 CFR 52
Topics: Air pollution control; Environmental protection; Incorporation by reference; Intergovernmental relations; Nitrogen oxides; Ozone; 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 environmental protection · Rules on incorporation by reference · Published in October 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.