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Sierra Club v. Environmental Protection Agency

ELR Citation: 51 ELR 20017
Nos. 15-1465, (D.C. Cir., 01/29/2021)

The D.C. Circuit vacated three provisions of EPA's 2018 rule implementing NAAQS for ozone. Environmental groups challenged four provisions of the rule: the interprecursor trading program, a provision allowing states to demonstrate compliance with the CAA's "reasonable further progress" milestone requirements through an implementation-based method, a provision allowing states to choose between two options for the reasonable further progress baseline year, and a provision allowing nonattainment areas to use already implemented measures to satisfy the Act's contingency measures requirements. The court found that the interprecursor trading program and EPA's interpretation of the CAA's contingency measures requirements contravened the Act's unambiguous language and that the provision implementing the milestone compliance demonstration requirement rested on an unreasonable interpretation of the Act, but that the provision allowing states to choose between two alternative years was based on a reasonable interpretation of an ambiguous baseline year provision. It therefore denied the groups' petition to review the provision concerning alternative baseline years, but vacated the other three provisions.