ELR Citation: 55 ELR 20111
No(s). 23-9503 (10th Cir. Aug 12, 2025)

The Tenth Circuit granted in part and denied in part a challenge to EPA's approval of Colorado's 2019 SIP revisions. An environmental group argued the revisions, which changed the wording of a permit requirement for new emission sources and added to the definition of a key threshold to evaluate compliance, prevented regulators from blocking construction when a new source would generate excessive emissions and allowed them to disregard emissions during drilling, fracking, and well completion. The court concluded the group did not show an effect from the revised wording in the permit requirement, but found that EPA acted arbitrarily and capriciously by failing to address the potential emissions during drilling, fracking, and well completion. It denied the petition as to the revised permit requirement, but granted it as to the revised definition of "commencement of operation" and remanded to EPA for further explanation.