Finding of Failure to Attain the 1987 24-Hour PM10 Standards; Pinal County, Arizona

The Environmental Protection Agency (EPA) is taking final action to determine that the West Pinal County, Arizona nonattainment area ("West Pinal County" or "area") did not attain the 1987 24- hour national ambient air quality standards (NAAQS or "standards") for particulate matter with a diameter of 10 micrometers or smaller (PM<INF>10</INF>) by its December 31, 2022 "Serious" area attainment date. This action is based on the EPA's calculation of the PM<INF>10</INF> design value for the nonattainment area over the 2020- 2022 period, using complete, quality-assured, and certified PM<INF>10</INF> monitoring data. With this final determination that West Pinal County has failed to attain the PM<INF>10</INF> NAAQS by its attainment date, the State of Arizona is required to submit a revision to the Arizona state implementation plan (SIP) that, among other elements, provides for expeditious attainment of the PM<INF>10</INF> standards and for a five percent annual reduction in the emissions of direct PM<INF>10</INF> or a PM<INF>10</INF> plan precursor pollutant in the nonattainment area.