Syllabus

NOTE: Where it is feasible, a syllabus (headnote) will be released, as is being done in connection with this case, at the time the opinion is issued. The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience of the reader. See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337.

SUPREME COURT OF THE UNITED STATES

Syllabus

CITY AND COUNTY OF SAN FRANCISCO, CALIFORNIA v. ENVIRONMENTAL PROTECTION AGENCY CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR THE NINTH CIRCUIT

No. 23–753. Argued October 16, 2024—Decided March 4, 2025 Under the Clean Water Act (CWA), 33 U. S. C. §1151 et seq., the Envi- ronmental Protection Agency (EPA) and authorized state agencies is- sue permits that impose requirements on entities that wish to dis- charge “pollutants” into the waters of the United States. A critical component of the CWA regulatory scheme is the National Pollutant Discharge Elimination System (NPDES), which makes it unlawful to discharge pollutants into covered bodies of water unless authorized by permit. EPA v. California ex rel. State Water Resources Control Bd., 426 U. S. 200, 205. These permits typically include “effluent limita- tions” on discharges that restrict the “quantities, rates, and concentra- tions of chemical, physical, biological, and other constituents.” §1362(11). Failure to comply with permit limitations exposes permit- tees to civil penalties and even criminal prosecution. §§1319(c) and (d). Under what is known as the “permit shield” provision, however, an entity that adheres to the terms of its permit is deemed to be com- pliant with the Act. §1342(k). This case involves a challenge to “end-result” requirements—permit provisions that do not spell out what a permittee must do or refrain from doing but instead make a permittee responsible for the quality of the water in the body of water into which the permittee discharges pollutants. The City of San Francisco operates two combined wastewater treatment facilities that process both wastewater and stormwater. Combined Sewer Overflow (CSO) Control Policy, 59 Fed. Reg. 18689; 75 F. 4th 1074, 1082 (CA9). During periods of heavy pre- cipitation, the combination of wastewater and stormwater may exceed the facility’s capacity, and the result may be the discharge of untreated 2 CITY AND COUNTY OF SAN FRANCISCO v. EPA

Syllabus

water, including raw sewage, into the Pacific Ocean or the San Fran- cisco Bay. 59 Fed. Reg. 18689; EPA, Office of Water, Combined Sewer Overflows: Guidance for Permit Writers, p. 1–1; 75 F. 4th, at 1082– 1083. In 1994, the EPA adopted its CSO Control Policy, which requires municipalities with combined systems to take prescribed measures and to develop and implement a Long-Term Control Plan, and provides for a two-phase permitting process. 59 Fed. Reg. 18691, 18696. For many years, San Francisco’s NPDES permit for its Oceanside facility was renewed without controversy, but in 2019, the EPA issued a renewal permit that added two end-result requirements. 75 F. 4th, at 1084–1085. The first of these prohibits the facility from making any discharge that “contribute[s] to a violation of any applicable water quality standard” for receiving waters. Id., at 1085. The second pro- vides that the City cannot perform any treatment or make any dis- charge that “create[s] pollution, contamination, or nuisance as defined by California Water Code section 13050.” Ibid. (internal quotation marks omitted). San Francisco argued that the end-result require- ments exceed EPA’s statutory authority, but the Ninth Circuit denied the city’s petition for review.