# 2025-09999: EPA Says Mariposa County Met Its Ozone Deadline

2025-09999, Determination of Attainment by the Attainment Date; California; Mariposa County; 2015 8-Hour Ozone National Ambient Air Quality Standards, is a Federal Register proposed rule from Environmental Protection Agency published 2025-06-03, effective Comments must be received by July 3, 2025.; PRIA reads it as touching household money (as of 2026-10-27).

- Canonical: https://policyrisk.com/federal-register/2025-09999
- As of: 2026-10-27
- Plain-text twin of the page above; the HTML and this file carry the same facts.

## Facts
- Document number: 2025-09999
- Title: Determination of Attainment by the Attainment Date; California; Mariposa County; 2015 8-Hour Ozone National Ambient Air Quality Standards
- Type: Proposed Rule
- Agencies: Environmental Protection Agency
- Citation: 90 FR 23501
- Published: 2025-06-03
- Effective: Comments must be received by July 3, 2025.
- Comments close: not stated
- Significant: no
- Touches household money: yes
- Regulation identifier numbers: none
- Last updated: 2026-10-27

## In one line

EPA Says Mariposa County Met Its Ozone Deadline

## Summary

The EPA says Mariposa County, California, met the 2015 ozone air quality standards by the August 3, 2024 deadline. They decided some high ozone days in 2021 and 2022 don’t count because of unusual events. This means cleaner air rules are working, and no extra costs or penalties will hit the community right now.

## Abstract

The Environmental Protection Agency (EPA) is proposing to determine that the Mariposa County nonattainment area in California ("Mariposa area"), classified as "Moderate" for the 2015 ozone national ambient air quality standards (NAAQS or "standard"), attained the 2015 ozone NAAQS by the August 3, 2024 attainment date. Our proposed determination of attainment is based upon the exclusion of exceedances of the 2015 ozone NAAQS that occurred on multiple days in 2021 and 2022, because the exceedances are due to exceptional events. This action, if finalized as proposed, will fulfill the EPA's statutory obligation to determine whether the Mariposa area attained the NAAQS by the August 3, 2024 attainment date.

## Effects PRIA read

- Mariposa met 2015 ozone standard: benefit, low. If you live in Mariposa County, EPA is proposing to determine the area met the 2015 ozone standard (0.070 parts per million) by the August 3, 2024 attainment date. The proposal is based on certified monitoring data for 2021–2023 that show a 3-year design value of 0.070 ppm when certain wildfire-rel…
- Wildfire exceedances excluded from regulatory counts: benefit, low. EPA concurred with California that certain ozone exceedances were caused by wildfire exceptional events and excluded the exceedances on August 7, 2021; August 27–28, 2021; and September 8–9, 2022 from regulatory use under the Exceptional Events Rule. EPA sent a concurrence letter dated February 19,…
- Contingency measures requirement suspended if finalized: benefit, low. If EPA finalizes the attainment determination, the State Implementation Plan (SIP) requirements to include attainment contingency measures and reasonable further progress (RFP) contingency measures for the 2015 ozone NAAQS will no longer apply to the Mariposa area for that standard. In other words,…
- No new federal costs or small-entity impacts from this action: benefit, low. EPA states this proposed action would not impose any additional Federal requirements, would not impose information collection burdens, and will not have a significant economic impact on a substantial number of small entities. The agency also states there are no unfunded mandates and no additional c…

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## Sources
- [2025-09999 on federalregister.gov](https://www.federalregister.gov/documents/2025/06/03/2025-09999/determination-of-attainment-by-the-attainment-date-california-mariposa-county-2015-8-hour-ozone)
- [2025-09999 as published (PDF)](https://www.govinfo.gov/content/pkg/FR-2025-06-03/pdf/2025-09999.pdf)

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Source: PRIA, https://policyrisk.com/federal-register/2025-09999 (as of 2026-10-27).