Approval and Promulgation of State Implementation Plans; State of Wyoming; Interstate Transport of Pollution for the 2006 24-Hour PM2.5

The Environmental Protection Agency (EPA) is approving portions of an August 19, 2011 State Implementation Plan (SIP) submission from the State of Wyoming that are intended to demonstrate that its SIP meets certain interstate transport requirements of the Clean Air Act (Act or CAA) for the 2006 24-hour fine particulate matter (PM 2.5 ) National Ambient Air Quality Standards (NAAQS). This submission addresses the requirement that Wyoming's SIP contain adequate provisions prohibiting air emissions that will have certain adverse air quality effects in other states. Specifically, EPA is approving the portion of the Wyoming SIP submission that addresses the significant contribution to nonattainment and interference with maintenance transport requirements for the 2006 24-hour PM 2.5  NAAQS. EPA is also approving the interference with prevention of significant deterioration (PSD) of air quality transport requirement for this NAAQS. EPA is not acting on the interference with visibility transport requirement at this time and will address the visibility requirement for this NAAQS in a separate future action.