Whether issued by an authorized State or the Environmental Protection Agency (“EPA”), a National Pollutant Discharge Elimination System (“NPDES”) permit issued under the Clean Water Act allows a permittee to discharge pollutants to waters of the United States (“WOTUS”). This week, the Supreme Court clarified in San Francisco v. EPA (Case No. 23-753) that the Clean Water Act (“CWA”) does not authorize permit conditions that require or prohibit an “end result,” such as causing or contributing to a nuisance or a violation of water quality standards in a receiving waterbody.

NPDES permits authorize discharges into WOTUS, subject to conditions, which may include restrictions on the amount or concentration of pollutants in the discharge, requirements for best management practices, and requirements for monitoring and reporting. The CWA does not, however, grant the authority to generally enforce the desired water quality of a receiving water body as a permit limitation. The Court reasoned that a limitation and the result of that limitation are fundamentally different. Furthermore, the applicable water quality standards incorporated into such “end result” requirements may change more often than the NPDES permit, causing a new limitation to come into effect that was never contemplated and with no opportunity for a compliance schedule.

San Francisco’s NPDES permit is illustrative. The first disputed condition prohibited any discharge that would cause or “contribute to a violation of any applicable water quality standard” for the receiving waters. The second condition prohibited San Francisco from treating or discharging water that “create[s] pollution, contamination, or nuisance as defined by California Water Code section 13050.” Neither of these conditions spell out what permittees must do, or refrain from doing, to avoid liability under the CWA. Both conditions, instead, attach liability if the EPA determines that the receiving water is exceeding water quality standards and the permittee’s discharge contributes at all to that exceedance, even if the permittee did everything the NPDES permit said to do.

The CWA includes a “permit shield” that deems compliance with an NPDES permit to be compliance with the CWA. The Court’s decision in San Francisco v. EPA recognizes that permittees must have this assurance, so if they do what the permit requires, they will not be met with crushing fines or criminal liability. The Court also recognized that this interpretation of the CWA will not cause EPA to lose its ability to supervise the permittee’s behavior or to protect water quality, because authority exists to impose detailed implementation activities, best management practices, and/or specific numeric and narrative limitations to reach the same end.

The Supreme Court’s decision in San Franciso v. EPA will require permittees and regulators to evaluate whether NPDES permit conditions are unauthorized and improper “end-result” conditions.  Future permits may include more prescriptive detail about activities that must be undertaken to protect water quality or additional numeric or narrative effluent limitations, if warranted. However, unlike the “end result” requirements, if new limits are imposed and not immediately attainable, then the permittee should be able to request a schedule to allow time to come into compliance.