ELR Citation: 53 ELR 20136
No(s). 14-9529 (10th Cir. Aug 15, 2023)

The Tenth Circuit affirmed in part and vacated in part EPA's partial approval and partial disapproval of Wyoming's SIP addressing emissions at coal-fired power plants to reduce regional haze. EPA approved the SIP as to the Naughton plant, but disapproved it for the Wyodak plant, and substituted, through a federal implementation plan, its determination of the proper technology to install there. The state of Wyoming and the plants' operator argued EPA should have approved the entire SIP and failed to grant Wyoming deference required by federal law when it disapproved the Wyodak portion. The court found EPA erred in evaluating the Wyodak portion because it treated non-binding guidances as mandatory in violation of the CAA, but that the Agency properly approved the state's determination of the best technology for the Naughton plant. It vacated and remanded EPA's disapproval of the Wyodak portion of the SIP, but upheld its approval of the Naughton portion.