Proposed rule · 2025-11263

Air Plan Approval; Colorado; Serious Attainment Plan RACT Requirements for the 2008 8-Hour Ozone National Ambient Air Quality Standards for the Denver Metro/North Front Range Nonattainment Area

The Environmental Protection Agency (EPA) is proposing to approve state implementation plan (SIP) submittals under the Clean Air Act (CAA) that address Reasonably Available Control Technology (RACT) requirements for the 2008 ozone National Ambient Air Quality Standards (NAAQS) for the Denver Metro/North Front Range (DMNFR) ozone nonattainment area. The requirements at issue relate to the area's previous Serious nonattainment classification. The EPA is proposing approval of the RACT SIP submittals, proposing to find that the State has met the applicable CAA requirements for Serious area RACT, and proposing that the State has addressed EPA's prior disapproval concerning specific RACT determinations. In this issue of the Federal Register the EPA is concurrently making an interim final determination to defer application of CAA sanctions associated with the prior disapproval. The EPA is taking this action pursuant to the CAA.