Approval and Promulgation of Implementation Plans; Idaho and Washington; Interstate Transport of Pollution

EPA is approving the actions of the Idaho Department of Environmental Quality (IDEQ) and the Washington State Department of Ecology (Ecology) to address the provisions of Clean Air Act section 110(a)(2)(D)(i) for the 8-hour ozone and PM<INF>2.5</INF> National Ambient Air Quality Standards (NAAQS). These provisions require each state to submit a State Implementation Plan (SIP) revision that prohibits emissions that adversely affect another state's air quality through interstate transport. IDEQ and Ecology have each adequately addressed the four distinct elements related to the impact of interstate transport of air pollutants for their states. These include prohibiting emissions that contribute significantly to nonattainment of the NAAQS in another state, interfere with maintenance of the NAAQS by another state, interfere with plans in another state to prevent significant deterioration of air quality, or interfere with efforts of another state to protect visibility.