Air Plan Approval; Colorado; 2017 Base Year Inventory and Emission Statement Rule Marginal Nonattainment Requirements, Revisions to Regulation 3

The Environmental Protection Agency (EPA) is approving elements of state implementation plan (SIP) revisions submitted by the State of Colorado on July 27, 2020, March 22, 2021, and June 26, 2023, to meet certain Clean Air Act (CAA) requirements related to the Denver Metro/North Front Range (DMNFR) area's classification as Marginal nonattainment for the 2015 8-hour ozone national ambient air quality standards (NAAQS). The revisions contain a base year emissions inventory for the nonattainment area and certify that the State's existing Air Pollutant Emission Notice (APEN) program for stationary sources fulfills the CAA's emission statement rule requirement. The revisions also include a new requirement for annual certification of APEN reported emissions for certain stationary sources. Unrelated to Colorado's Marginal ozone nonattainment obligations, the EPA is also approving the State's revisions to Regulation Number 3 concerning an update to the date of incorporation by reference of global warming potentials used in the computation of the carbon dioxide equivalent for comparing emissions from various greenhouse gases (GHGs). The EPA is taking this action pursuant to the CAA.