On March 4, 2025, the United States Supreme Court issued its decision (linked below) in the City and County of San Francisco v. EPA case holding that NPDES permit conditions the Court characterized as “end-result” requirements exceed USEPA's authority under the Clean Water Act (CWA).  Writing for the 5-4 majority, Justice Alito interpreted Sec. 1311(b)(1)(C) of the Act and concluded that two conditions of the NPDES permit covering the City's discharge from a combined sewer treatment plant were problematic under the Court's interpretation of the CWA. The invalidated conditions prohibit discharges that (i) contribute to a violation of a water quality standard or (ii) create “pollution, contamination, or nuisances” as defined by California state law.  Among other things, the Court was troubled by the significant enforcement risk permittees face (in particular in the context of multiple dischargers to the same receiving waters) in the application of such vague compliance conditions. 

Permittees should review the language of their permits for such “end-result” requirements and evaluate their validity in light of this decision, mindful that state law could govern the analysis in those states with delegated permitting authority and supplemental state statutory authority.