The Environmental Protection Agency (EPA) is approving a source-specific State Implementation Plan (SIP) revision submitted by the Washington State Department of Ecology (Ecology) on December 18, 2020. The SIP revision makes changes to nitrogen oxide control requirements for the TransAlta Centralia Generation Plant (TransAlta). These requirements were established in an order issued to TransAlta by the State to satisfy the Clean Air Act Best Available Retrofit Technology Requirements (BART) put in place by Congress to reduce regional haze and restore visibility in national parks and wilderness areas. The changes submitted by the State improve the operation of pollution control equipment at TransAlta while continuing to meet BART requirements.