Approval and Promulgation of Implementation Plans; Designation of Areas for Air Quality Planning Purposes; State of California; PM-10; Determination of Attainment for the Coso Junction Nonattainment Area; Determination Regarding Applicability of Certain Clean Air Act Requirements

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EPA is proposing to determine that the Coso Junction nonattainment area (CJNA) in California has attained the 24-hour National Ambient Air Quality Standard (NAAQS) for particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM-10). This proposed determination is based upon monitored air quality data for the PM-10 NAAQS during the years 2006- 2008. In addition, data for 2009 contained in EPA's Air Quality System (AQS) shows the CJNA continued to attain the PM-10 NAAQS through 2009, and preliminary data for 2010 available to date show no exceedances of the 24-hour NAAQS have been recorded at the CJNA monitoring site. EPA is also proposing to determine that, because the CJNA has attained the PM-10 NAAQS, the obligation to make submissions to meet certain Clean Air Act (CAA or the Act) requirements is not applicable for as long as the CJNA continues to attain the PM-10 NAAQS.