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

Pursuant to section 107(d)(3) of the Clean Air Act, the EPA is redesignating from "unclassifiable" to "nonattainment" an area in western 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<INF>10</INF>), and therefore also revising the boundaries of the existing "rest of state" unclassifiable area. The EPA's establishment of this new PM<INF>10</INF> nonattainment area, referred to as "West Pinal," is based on numerous recorded violations of the PM<INF>10</INF> standard at various monitoring sites within the county. With the exception of Indian country and certain Federal lands, the EPA's nonattainment area boundaries generally encompass the land geographically located within Pinal County north of the east-west line defined by the southern line of Township 9 South, Gila and Salt River Baseline and Meridian, and west of the north-south line defined by the eastern line of Range 8 East, except where the boundary extends farther east in the Florence and Picacho Peak areas. The effect of this action is to establish and delineate a new PM<INF>10</INF> nonattainment area within Pinal County and thereby to impose certain planning requirements on the State of Arizona to reduce PM<INF>10</INF> concentrations within this area, including, but not limited to, the requirement to submit, within 18 months of redesignation, a revision to the Arizona state implementation plan that provides for attainment of the PM<INF>10</INF> standard as expeditiously as practicable but no later than the end of the sixth calendar year after redesignation.