As previously reported, a coalition of environmental groups recently filed a petition for review in the D.C. Circuit Court of Appeals (D.C. Circuit) challenging the U.S. Environmental Protection Agency’s (EPA) recent final rule titled, “Hazardous and Solid Waste Management System: Disposal of CCR; A Holistic Approach to Closure Part B: Alternate Demonstration for Unlined Surface Impoundments,” 85 Fed. Reg. 72,506 (Nov. 12, 2020). Commonly called “Part B,” the rule allows owners and operators to submit demonstrations showing their clay-lined impoundments are adequately protective of human health and the environment. The environmental groups filed the petition, however, outside the 90-day timeframe in which parties may seek review of regulations promulgated under RCRA. 42 U.S.C. § 6976(a)(1). In light of their untimeliness, on February 25, the environmental groups filed a