Approval and Promulgation of Implementation Plans; Colorado; Revisions to Regulation Number 7; Aerospace, Oil and Gas, and Other RACT Requirements for the 2008 8-Hour Ozone Standard for the Denver Metro/North Front Range Nonattainment Area

Subject to certain exceptions, the Environmental Protection Agency (EPA) is approving State Implementation Plan (SIP) revisions submitted by the State of Colorado on May 14, 2018, May 8, 2019, May 13, 2020 and March 22, 2021. The revisions are to Colorado Air Quality Control Commission (Commission or AQCC) Regulation Number 7 (Reg. 7). The revisions to Reg. 7 address Colorado's SIP obligation to require reasonably available control technology (RACT) for sources covered by the 2016 oil and natural gas control techniques guidelines (CTG or CTGs) for nonattainment areas classified as Moderate and above under the 2008 ozone National Ambient Air Quality Standard (NAAQS); update RACT requirements for major sources of volatile organic compounds (VOC) and nitrogen oxides (NO<INF>X</INF>); reorganize the regulation; add incorporation by reference dates to rules and reference methods; and make typographical, grammatical, and formatting corrections. Also, the EPA is finalizing approval of the State's negative declaration that there are no sources in the Denver Metro/North Front Range (DMNFR) Area subject to the aerospace CTG, which was conditionally approved in our February 24, 2021 rulemaking. Finally, we are taking no action today on several specific portions of the State submittals, as further explained below. The EPA is issuing this final rule pursuant to the Clean Air Act (CAA).