March/April 2025 Issue

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US Supreme Court Imposes Limitations on “End Result” Provisions in NPDES Permits

Jared Walker Smith | 04.16.25

On March 4, 2025, a divided U.S. Supreme Court (SCOTUS) held that the Clean Water Act (CWA) does not authorize the Environmental Protection Agency (EPA) to impose what it termed ​“end result” limitations in National Pollutant Discharge Elimination System (NPDES) permits. SCOTUS’s decision in City and County of San Francisco, California v. Environmental Protection Agency, 604 U.S. ____, 145 S.Ct. 704 (2025) (San Francisco) could have a limited impact in Wisconsin.

The Wisconsin Department of Natural Resources (DNR) has delegated authority under the CWA to issue NPDES permits — called Wisconsin Pollutant Discharge Elimination System (WPDES) permits. These WPDES permits are issued pursuant to the CWA and implementing Wisconsin statutes and regulations. Since much of the state program is tied to the federal CWA, a SCOTUS clarification of the CWA can directly impact Wisconsin’s implementation of its own statutes and regulations.

The CWA and NPDES Permit Program

Understanding how NPDES permits control discharges is crucial to understanding SCOTUS’s holding. The NPDES permit program was created by the CWA to regulate point sources that discharge pollutants to surface waters. One example of a point source is the outfall of a wastewater treatment plant, like that at issue in San Francisco. EPA tailors an individual NPDES permit to a particular facility discharging into a particular water body and considers the type of facility activity, nature of discharge, and receiving water quality.

Under the CWA, there are two types of ​“effluent limitations” included in an NPDES permit: technology based effluent limitations (TBELs) and water quality based effluent limitations (WQBELs). TBELs are standards for effluent quality based on available treatment technologies. WQBELs are set without regard to cost or technology availability and permit only those discharges that may be made without unduly impairing water quality in the receiving water.

In addition to TBELs and WQBELs, NPDES permits may include ​“any more stringent limitation.” These non-effluent ​“other limitations” imposed by NPDES permits may include narrative limitations such as best management practices (BMPs) that aim to prevent or minimize the potential for the release of toxic pollutants or hazardous substances in significant amounts to surface waters.

NPDES permittees that do not comply with permit terms are subject to significant civil penalties and, potentially, even criminal penalties. However, permittees that comply with their NPDES permits are deemed in compliance with the CWA and are shielded from liability if a surface water becomes impacted. This is often referred to as the ​“permit shield” provision.

Case Background and Holding

In 2019, EPA issued a renewal NPDES permit to the City of San Francisco’s combined wastewater and stormwater treatment facilities. The renewal permit included two new provisions. The first new provision prohibited any discharge ​“that contribute[s] to a violation of any applicable water quality standard” for receiving waters. The second prohibited the City from performing any treatment or making any discharge that ​“create[s] pollution, contamination, or nuisance” as defined in California law.

The City challenged these ​“end-result” provisions in the NPDES permit, arguing that they exceeded the EPA’s statutory authority. The Ninth Circuit denied the city’s petition for review, holding that the CWA authorized ​“EPA to impose ​‘any’ limitations ensuring applicable water quality standards are satisfied in a receiving body of water.”

A divided SCOTUS reversed, holding that while not all ​“limitations” under the CWA must qualify as effluent limitations, the authorization to impose ​“any more stringent limitations” does not extend to ​“end-result” provisions. At issue was what qualifies as a ​“limitation” under the CWA and NPDES permit program. SCOTUS determined that a limitation must tell a permittee ​“that it must do a certain specific thing[].” In other words, to be a limitation, a provision must set out actions that must be taken to achieve an objective (e.g., meeting water quality standards). Under the majority’s interpretation, a ​“limitation” cannot leave it up to the permittee to identify the steps the permittee must take to ensure water quality standards are met in the receiving water.

The SCOTUS majority bolstered this interpretation by distinguishing the current CWA, which provides the ​“permit shield” to compliant permittees, from prior federal pollution control legislation, which held a discharger potentially liable if the quality of the water into which it discharged pollutants failed to meet water quality standards. The Court found that unless a permittee knew what actions it must take to comply with its permit, the permit shield protections ​“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.” San Francisco at 718. The Court found this result even more troubling where there are multiple dischargers (perhaps hundreds) into the same waterbody — and chose not to interpret the CWA differently for single-discharger cases, like San Franciscos, from these multiple-discharger scenarios. While end-result limitations are prohibited, SCOTUS confirmed that the CWA continues to allow non-numerical (i.e. ​“narrative”) form limitations, like BMPs and ​“operational requirements and prohibitions” in addition to numerical limitations (TBELs and WQBELs). The majority emphasized that ​“EPA possesses the expertise … and the resources necessary to determine what a permittee should do,” and issue permits without end-result provisions that meet with CWA’s objectives of protecting water quality. Id. at 719.

Dissent

Justice Barrett, joined by Justices Sotomayor, Kagan, and Jackson, joined the portion of the decision confirming that non-numerical form limitations are allowed but otherwise dissented. The dissent found that there was nothing novel about a limitation imposing that a particular result must be achieved and then leaving it up to the permittee to figure out what it must do. As one example, the dissent cited to congressional spending ​“limitations” that require a branch of government to figure out how not to spend more than it is budgeted.
Ultimately, the four justices would have held that ​“end-result” receiving water limitations qualify as ​“limitations” that are entirely consistent with the CWA provisions. Instead, the dissent argues that the result of the majority’s holding will be more onerous permitting processes, more specialized terms in permits, and delays in issuing new permits.

Impact in Wisconsin

Wisconsin generally includes broad WQBELs, TBELs, and BMPs in its WPDES permits to ensure that water quality standards are met. Regulations require that, in issuing WPDES permit conditions to protect water quality, the combined impacts of multiple dischargers are considered in setting individual permit limitations. Wisconsin also includes certain provisions that are more stringent than the CWA, such as regulating phosphorous. These existing numerical and narrative limitations are not impacted by San Francisco.

However, DNR includes at least one standard permit condition in WPDES permits that may run afoul of the San Francisco holding. This ​“Surface Water Uses and Criteria” provision generally provides as follows:

In accordance with NR 102.04, Wis. Adm. Code, surface water uses and criteria are established to govern water management decisions. Practices attributable to municipal, industrial, commercial, domestic, agricultural, land development or other activities shall be controlled so that all surface waters including the mixing zone meet the following conditions at all times and under all flow and water level conditions:

a. Substances that will cause objectionable deposits on the shore or in the bed of a body of water, shall not be present in such amounts as to interfere with public rights in waters of the state.

b. Floating or submerged debris, oil, scum or other material shall not be present in such amounts as to interfere with public rights in waters of the state.

c. Materials producing color, odor, taste or unsightliness shall not be present in such amounts as to interfere with public rights in waters of the state.

d. Substances in concentrations or in combinations which are toxic or harmful to humans shall not be present in amounts found to be of public health significance, nor shall substances be present in amounts which are acutely harmful to animal, plant or aquatic life.

While the underlying Wis. Admin. Code § NR 102.04(1) reasonably establishes a policy that discharges should be controlled to meet certain conditions at all times, it is likely that a reviewing court, citing to San Francisco, could find that the blanket inclusion of this language in a WPDES permit subjects a permittee to a disallowed ​“end-result” provision.

In the end, municipal dischargers may have to wait and see how San Francisco plays out in current and future Wisconsin WPDES permits — and if the dissent’s prediction proves to be correct that ​“it will be more difficult and more time consuming” for the DNR to issues these permits.