By Davin A. Widgerow, Partner at Burke, Williams & Sorensen, LLP
Published in the Daily Journal on March 29, 2025
The federal Water Pollution Prevention and Control Act, commonly known as the Clean Water Act, controls water pollution by requiring discharging parties to secure permits controlling the amounts of pollutants they release into waterbodies. In City and County of San Francisco v. U.S. Environmental Protection Agency (2025) 2025 WL 676441, the U.S. Supreme Court voided a significant component of these permits—and perhaps a significant source of liability for public agencies in the process.
What are Clean Water Act NPDES permits?
The Clean Water Act permit at issue in the San Francisco case is a National Pollutant Discharge Elimination System, or NPDES, permit (see 33 U.S.C. § 1342). Importantly, compliance with an NPDES permit constitutes compliance with the Clean Water Act—often referred to as the “permit shield”—while discharging into a waterbody without an NPDES permit, or in violation of an NPDES permit, is a violation of the Clean Water Act (Id. at § 1342(k)). Such violations are strict liability violations, and liability can be imposed without regard to intent or fault. (Id. at § 1311(a); see also United States v. Earth Sciences, Inc. (10th Cir. 1979) 599 F.2d 368, 374.)
All NPDES permits contain at least four components:
- Effluent and other pollution limitations, which set limits on pollutants in discharges to waterbodies;
- Monitoring and reporting requirements;
- Any special conditions, such as compliance schedules or unique studies; and
- Standard conditions, including administrative and enforcement provisions.
The San Francisco case concerns the pollution limitations component of NPDES permits. Effluent limitations are restrictions on the “quantities, rates, and concentrations of chemical, physical, biological, and other constituents” in discharges to waterbodies. (33 U.S.C. § 1362(11).) Effluent limitations can be:
- Numeric: impose actual numeric limits on pollutants (e.g., no more than 3.2 µg/L of lead per day).
- Narrative: non-numeric activities aimed at improving water quality (e.g., street sweeping, education campaigns, and trash control).
Pollution limitations are also divided based on the location they regulate:
- Technology-based effluent limitations: apply at the discharge point (e.g., the end of a sewage outfall pipe).
- Water-quality-based effluent limitations: imposed to meet water quality standards in the receiving water, not at the discharge point—also called “receiving water limitations.”
Receiving water limitations can also be numeric or narrative, and may not always identify specific effluent limits. They have been authorized when technology-based limitations fail to improve downstream water quality. The key statute, 33 U.S.C. § 1311(b)(1)(C), requires “any more stringent limitation… necessary to meet water quality standards.”
As noted, NPDES permit violations are strict liability offenses under the Clean Water Act. Violations can lead to civil penalties up to $67,000 per violation, per day (Id. at § 1319(d), as adjusted for inflation per 40 C.F.R. 19.4), as well as citizen suits.
What is the case about, and what did the court decide?
San Francisco operates a wastewater treatment facility that discharges treated wastewater into the Pacific Ocean under an NPDES permit. In 2019, its permit was revised to include two new generic receiving water limitations:
- Prohibited discharges that “contribute to a violation of any applicable water quality standard.”
- Prohibited treatment or discharges that “create pollution, contamination, or nuisance” under California Water Code § 13050.
San Francisco challenged these provisions, arguing:
- The phrase “any more stringent limitation” in the statute must refer to effluent limitations; thus, the generic receiving water limitations were impermissibly vague. The Court rejected this argument, saying the phrase included more than effluent limits—like narrative limits, equipment specs, or practices.
- The Act does not authorize generic permit requirements conditioning compliance on downstream water quality. The city argued this would make agencies liable for conditions beyond their control. The Court agreed, citing:
- The statutory term “limitation” refers to imposed conditions, not undefined end results.
- The Clean Water Act was meant to focus on discharge quality, not receiving water conditions.
- Holding agencies liable for downstream conditions would invalidate the permit shield.
- It fails to account for shared liability in multi-discharger scenarios.
The Court thus held § 1311(b)(1)(C) does not authorize generic receiving water limitations in NPDES permits.
Justice Barrett dissented, agreeing the phrase wasn’t limited to effluent limits but arguing that conditions forbidding water quality standard violations do count as limitations. She said vague or unfair limitations can be challenged under administrative law—not struck entirely.
What happens next?
The Court’s decision invalidates generic receiving water limitations in NPDES permits unless they include more detailed restrictions. The EPA warned this could lengthen permit processes, as regulators will need to draft more specific numeric limits. Some environmental advocates fear water quality will decline as a result, though others believe better-enforced numeric limits may develop.
For public agencies, the ruling reduces liability. Agencies that comply with NPDES permit terms may now be shielded from responsibility for downstream water conditions outside their control.
State regulators, such as those in California, may seek to adopt receiving water limitations through state law as a workaround.
Davin A. Widgerow is a partner at Burke, Williams & Sorensen, LLP.
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