Designation of Areas for Air Quality Planning Purposes; State of Arizona; Pinal County; PM10

Résumé

Pursuant to section 107(d)(3) of the Clean Air Act, EPA is proposing to redesignate from "unclassifiable" to "nonattainment" an area generally covering the western half of Pinal County, Arizona, for the 1987 national ambient air quality standard for particles with an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM 10 ), and therefore also proposing to revise the boundaries of the existing "rest of state" unclassifiable area. EPA's proposal to establish this new PM 10 nonattainment area, referred to as "West Pinal," is based on numerous recorded violations of the PM 10 standard at various monitoring sites within the county. EPA's proposed boundaries would encompass all land geographically located within Pinal County west of the north-south line defined by the boundary between Townships 10E and 11E, but excluding the main reservation of the Tohono O'odham Nation (TON) and excluding the Apache Junction portion of the existing Phoenix PM 10 nonattainment area. San Carlos Apache lands, which are located in the eastern quarter of the county, would be excluded from the proposed nonattainment area along with the rest of the eastern half of the county. If finalized a