Air Plan Approval and Conditional Approval; Colorado; Revisions to Regulation Numbers 7 and 21 and RACT Requirements for the 2008 8-Hour Ozone Standard for the Denver Metro/North Front Range Nonattainment Area

The Environmental Protection Agency (EPA) is proposing to approve and conditionally approve portions of a State Implementation Plan (SIP) submission from the State of Colorado dated May 3, 2024. The submission relates to Colorado Air Quality Control Commission (AQCC or Commission) Regulation Number 7 (Reg. 7) and Regulation Number 21 (Reg. 21), and addresses Colorado SIP obligations related to reasonably available control technology (RACT) requirements for sources in nonattainment areas for the 2008 ozone National Ambient Air Quality Standards (NAAQS). The EPA is taking this action pursuant to the Clean Air Act (CAA).