Decision Summary

On March 4, 2025 the U.S. Supreme Court reversed a Ninth Circuit decision and held that Section 1311(b)(1)(C) of the Clean Water Act (CWA) does not authorize the Environmental Protection Agency (EPA) to include “end-result” provisions in its National Pollutant Discharge Elimination System (NPDES) permits. According to the ruling, the EPA has authority to impose specific limitations and to describe actions that a permittee must take to ensure that water quality standards are met, but that authority does not allow the EPA to impose requirements on a permittee for the quality of the receiving water itself (i.e., end-result provisions). This decision will change issuance and enforcement of federally issued NPDES permits and could impact State issued permits.

Background

The case began with the City of San Francisco’s claim that two new non-numeric conditions added to their Wastewater Treatment Plant (WWTP) NPDES permit during a 2019 permit renewal were so ambiguous that it was impossible to tell if and when the City was in violation of those standards. The provisions at issue were:

• Discharge shall not cause or contribute to a violation of any applicable water quality standard… for receiving waters adopted by the Regional Water Board, State Water Resources Control Board (State Water Board), or U.S. EPA.
• Neither the treatment nor the discharge of pollutants shall create pollution, contamination, or nuisance as defined by California Water Code section 13050.

In 2023, the Ninth Circuit concluded that the EPA had authority under the CWA to impose the narrative conditions and in May 2024, the U.S. Supreme Court agreed to review the decision. On March 4, 2025, the Supreme Court issued a 5-4 ruling reversing the Ninth Circuit’s decision.

In the ruling, the Supreme Court refers to provisions directed at the quality of water in receiving waters as “end-result” requirements:

“[T]his case involves provisions that do not spell out what a permittee must do or refrain from doing; rather, they make a permittee responsible for the quality of the water in the body of water into which the permittee discharges pollutants. When a permit contains such requirements, a permittee that punctiliously follows every specific requirement in its permit may nevertheless face crushing penalties if the quality of the water in its receiving waters falls below the applicable standards. For convenience, we will call such provisions ‘end-result’ requirements.”

While the court considered several factors in the decision, such as statutory interpretation and the history of the CWA, the basis of the ruling boiled down to two key points as discussed in the majority opinion:

• Section 1311(b)(1)(C) does not authorize the EPA to include “end-result” provisions in NPDES permits. Determining what steps a permittee must take to ensure that water quality standards are met is the EPA’s responsibility, and Congress has given it the tools needed to make that determination. This responsibility cannot be shifted onto permittees through non-specific permit language.
• The benefit of the “permit shield” provision of 33 U.S.C. § 1342(k) of the CWA would be eviscerated if the EPA could impose a permit provision making the permittee responsible for any drop in water quality below the accepted standard. Because a permittee could do everything required by all the other permit terms and still face enforcement if the quality of the water in discharge receiving waters dropped below the applicable water quality levels, “end-result” limitations are inconsistent with the “permit shield”.

In addition to these arguments, the Court noted that the CWA, as adopted in 1972 to replace the Water Pollution Control Act (WPCA), conspicuously removed the “backward-looking” approach that had been the norm prior to 1972. In that approach, the EPA would identify polluted waters and then work backward to determine which entities contributed to the pollution. The CWA reverses that approach and prohibits any discharge of pollutants from a point source into navigable waters unless the discharge is authorized by a permit. NPDES permits are issued to authorize discharges and include limitations and requirements to control the amount of pollution in the discharge. The Court further noted that the CWA does not support a “backward-looking” approach because there is no mechanism to handle “the problem that arises when more than one permittee discharges into a body of water with substandard water quality.”

The Court did acknowledge that the term “limitations” is not limited to “effluent limitations”. “Effluent limitation” refers to a restriction “on quantities, rates, and concentrations of chemical, physical, biological, and other constituents which are discharged from point sources”. Other “limitations” can include narrative requirements such as best management practices and operational requirements. The Court clarified that certain narrative requirements are considered “limitations” while “end result” requirements are not because the first regulates the quality of the water that is being discharged while the second is aimed at the quality of the water that receives the discharge.

What Will Change With This Decision?

This decision requires the removal (or prevents enforcement) of NPDES permit provisions that include “end-result” requirements in which the permittee is responsible for the quality of the water that receives its discharge, as opposed to relying solely on permit provisions that regulate the quality of the water being discharged.

Overall, this change is considered a win for the regulated community, as it removes ambiguity, strengthens the permit shield, and reduces the threat of enforcement resulting from scenarios that may be out of the control of the permittee. However, there are potential negative impacts.

Historically, “end result” requirements have been used to require additional steps on the part of the permittee in case the specific effluent limitations and narrative permit requirements were not sufficient to protect the quality of the receiving water. Because the “end result” requirements were results based, permitees were left to determine the specific actions needed to protect the quality of the receiving water. This meant that the permittee had flexibility to implement a combination of treatment, controls, and/or Best Management Practices as needed to ensure compliance. If the EPA is required to include additional specific limitations for each facility, beyond the effluent limitations already considered, it is possible that the EPA will impose requirements that are more stringent than those a facility may have otherwise adopted.

This ruling shifts the burden of determining how water quality standards will be met back to the EPA. This reduces some of the burden for permittees but also means that additional time and resources will be needed for permit issuance as EPA gathers necessary information and develops specific numerical or narrative limitations for each permit. With current cuts to Federal agencies and staff, the increased analysis and development of limitations could mean a significantly longer timeframe for permit issuance.

Additional clarity in permit requirements is generally a positive thing. However, the shift towards additional prescriptive requirements and enforceable pollutant-discharge permit limitations removes some of the enforcement discretion implicit in more general permit conditions.

What Happens Next?

This ruling applies to NPDES permits issued under the CWA. For states with permitting authority under state law (which includes most states) the impact will vary by state. Depending on state law, a state could take no action or could use this ruling as a basis for moving away from the “end-result” limitations and replacing those with specific numeric limits.

Permittees impacted by the change can expect more prescriptive language in new or reissued NPDES Permits and changes to enforcement for existing permits. Moving toward the development of specific permit limitations will involve additional time and resources on the part of the EPA (or the State authority if applicable). This will likely slow the issuance of permits. The change could also impact General NPDES permits, which are intended to cover large sectors of covered facilities. It may be challenging to incorporate more specific requirements with the General Permit, although it has been noted that narrative limitations can be effectively substituted for the “end result” requirements.

Does your facility’s permit contain “end-result” limitations? If you would like to discuss how this decision could impact your current NPDES Permit or upcoming NPDES permitting activities, Trinity is available to support with answering any permitting questions as well as applying for a new permit. For more information on this topic, please contact Trinity Consultants directly to talk with a local expert.