Approval and Promulgation of Air Quality Implementation Plans; Colorado; Regional Haze State Implementation Plan

The Environmental Protection Agency (EPA) is approving State Implementation Plan (SIP) revisions submitted by the State of Colorado on May 26, 2017, addressing regional haze. The revisions include source-specific revisions to the nitrogen oxides (NOX) best available retrofit technology (BART) determination for Craig Station Unit 1 and to the NOX reasonable progress determination for the Nucla Station. Both Craig Station Unit 1 and Nucla Station are owned in part and operated by Tri-State Generation & Transmission Association, Inc. (Tri-State). The EPA is taking this action pursuant to section 110 of the Clean Air Act (CAA).