Determinations of Attainment by the Attainment Date, California Areas Classified as Serious for the 2008 Ozone National Ambient Air Quality Standards and Marginal for the 2015 Ozone National Ambient Air Quality Standards

The Environmental Protection Agency (EPA) is proposing to determine that the Nevada County (Western part) and Ventura County areas in California, both classified as Serious for the 2008 ozone National Ambient Air Quality Standards (NAAQS), attained the 2008 ozone NAAQS by the July 20, 2021 attainment date. The EPA is also proposing to determine that six areas in California classified as Marginal for the 2015 ozone NAAQS, attained the 2015 ozone NAAQS by the August 3, 2021 attainment date. These six areas are: Butte County, Calaveras County, San Luis Obispo (Eastern part), Sutter Buttes, Tuolumne County, and Tuscan Buttes. Our proposed determination of attainment is based on the exclusion of exceedances of the 2008 and 2015 ozone NAAQS that occurred on multiple days in 2018 and 2020, because the exceedances are due to exceptional events. We are further proposing to find that, if we finalize these proposed determinations of attainment by the attainment date for the Nevada County (Western part) and Ventura nonattainment areas, then the requirement for the state to have contingency measures for Reasonable Further Progress (RFP) and attainment for the 2008 ozone NAAQS for these areas will no longer apply, because the contingency measures would never be needed given the attainment of the NAAQS. This action, if finalized as proposed, will fulfill the EPA's statutory obligation to determine whether these ozone nonattainment areas attained the NAAQS by the relevant attainment date.