( April 30, 2025, 3:23 PM EDT) -- DENVER — A panel of the 10th Circuit U.S. Court of Appeals partially granted and partially denied an environmental group’s petition for review of the U.S. Environmental Protection Agency’s action related to Colorado’s state implementation plan (SIP) for keeping air pollutants below the National Ambient Air Quality Standards (NAAQS), remanding the issue to the EPA for further explanation of its decision to approve a revised definition of the term “commencement of operation.” The SIP has particular application with regard to emissions associated with hydraulic fracturing activity....