Proposed rule · 2025-09999

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

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.