The Northern Sierra Air Quality Management District adopted the Reasonably Available Control Technology (RACT) State Implementation Plan (SIP) Revision for Western Nevada County 8-Hour Ozone Nonattainment Area (2018 RACT SIP) on March 26, 2018. CARB submitted the 2018 RACT SIP to the U.S. EPA as a revision to the California SIP on June 7, 2018.