EPA Says Mariposa County Met Its Ozone Deadline
Published Date: 6/3/2025
Proposed Rule
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.
Analyzed Economic Effects
4 provisions identified: 4 benefits, 0 costs, 0 mixed.
Mariposa met 2015 ozone standard
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-related exceedances are excluded.
Wildfire exceedances excluded from regulatory counts
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, 2025 and used the exclusions in calculating the 2021–2023 design value.
Contingency measures requirement suspended if finalized
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, contingency measures tied to failure to attain by the August 3, 2024 attainment date would not be required to be implemented.
No new federal costs or small-entity impacts from this action
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 costs to state, local, Tribal governments, or the private sector from this action.
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Key Dates
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