The Environmental Protection Agency (EPA) is approving a state implementation plan (SIP) revision submitted by the State of Colorado. The submittal certifies that the State of Colorado has fulfilled, through previous SIP revisions, Nonattainment New Source Review (NNSR) Permit Program requirements under the 2015 8-hour ozone National Ambient Air Quality Standards (NAAQS) for the Denver Metro/North Front Range (DMNFR) area. The State of Colorado submitted the certification to meet the nonattainment requirements for Marginal ozone nonattainment areas (NAAs) for the 2015 8-hour ozone NAAQS. The EPA is taking this action pursuant to sections 110, 172, 173, and 182 of the Clean Air Act (CAA).