Promulgation of State Implementation Plan Revisions; Colorado; Attainment Demonstration for the 2008 8-Hour Ozone Standard for the Denver Metro/North Front Range Nonattainment Area, and Approval of Related Revisions

On May 31, 2017, the State of Colorado submitted State Implementation Plan (SIP) revisions related to attainment of the 2008 8-hour ozone National Ambient Air Quality Standards (NAAQS) for the Denver Metro/North Front Range (DMNFR) Moderate nonattainment area by the applicable attainment date of July 20, 2018. The Environmental Protection Agency (EPA) proposes to approve the majority of the submittal, which includes an attainment demonstration, base and future year emission inventories, a reasonable further progress (RFP) demonstration, a reasonably available control measures (RACM) analysis, a motor vehicle inspection and maintenance (I/M) program in Colorado Regulation Number 11 (Reg. No. 11), a nonattainment new source review (NNSR) program, a contingency measures plan, 2017 motor vehicle emissions budgets (MVEBs) for transportation conformity, and revisions to Colorado Regulation Number 7 (Reg. No. 7). The EPA is also proposing to approve portions of the reasonably available control technology (RACT) analysis. Finally, the EPA proposes to approve revisions made to Colorado's Reg. No. 7 in a May 5, 2013 SIP submission. This action is being taken in accordance with the Clean Air Act (CAA).