The Environmental Protection Agency (EPA or ``Agency'') is determining that the Imperial County nonattainment area would have attained the 2015 ozone national ambient air quality standard (NAAQS) by the August 3, 2021 ``Marginal'' area attainment date, but for emissions emanating from outside the United States. As a result of this final action, the Imperial County nonattainment area will no longer be subject to the Clean Air Act (CAA) requirements pertaining to reclassification upon failure to attain and therefore will remain classified as a Marginal nonattainment area for the 2015 ozone NAAQS. This action discharges the EPA's statutory obligation to determine whether the Imperial County ozone nonattainment area attained the NAAQS by the attainment date.