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Supreme Court expands reach of Clean Water Act to cover some discharges to groundwater

Sara Chamberlain Paul Sonderegger April 28, 2020

On April 23, 2020, the United States Supreme Court adopted a new flexible standard that expands the reach of the Clean Water Act (CWA). In a 6-3 decision, the Court held that the CWA requires a permit “when there is the functional equivalent of a direct discharge” from a point source into navigable waters. County of Maui v. Hawai’i Wildlife Fund, 590 U.S. __ (2020). Under this standard, discharges originating from a point source that travel to navigable waters through a nonpoint source, such as groundwater, may now require a permit. This decision could have costly consequences for manufacturers, utilities, energy and petroleum companies, municipalities and the regulated community generally.


The CWA generally prohibits the discharge of a pollutant “to navigable waters from any point source” absent a permit issued in accordance with the National Pollutant Discharge Elimination System (NPDES). 33 U.S.C. § 1362(12)(A); 33 U.S.C. § 1311(a); 33 U.S.C. § 1342. Point sources include “any discernible, confined and discrete conveyance…from which pollutants are or may be discharged” including pipes, ditches, tunnels, conduits, wells, fissures, containers, rolling stock, concentrated animal feeding operations and vessels (among others). Id. at § 1362(14). Thus, absent a permit or other exception, a party violates the CWA when it discharges a pollutant from a point source to a navigable water.

Until recently, the CWA’s prohibition on discharges, and requirement to obtain an NPDES permit, appeared to apply only to direct discharges to navigable waters or to surface waters that had a significant nexus or connection to navigable waterways—not to discharges to groundwater. See Kelley ex rel. Michigan v. United States, 618 F.Supp. 1103, 1105 (W.D. Mich. 1985) (noting that DOJ argued that “the regulatory and enforcement aspects of the Clean Water Act were not designed to control the discharge of pollutants into the soil and groundwater”). The Court’s decision in County of Maui changes the analysis.

In 2012, several environmental groups brought a CWA citizen’s suit against the County of Maui, Hawaii, claiming that the County violated the CWA by discharging pollutants to navigable waters without a permit. Hawai’i Wildlife Fund v. County of Maui, 24 F.Supp.3d 980, 998 (Haw. 2014). The County pumped approximately 4 million gallons of wastewater per day into four underground injection wells. Significant volumes of this wastewater migrated from the wells through groundwater to the Pacific Ocean, a distance of approximately half a mile. The district court ruled in favor of the environmental groups, finding that, because the “path to the ocean is clearly ascertainable,” the discharge from the well to groundwater was “functionally one into navigable water” and thus triggering the permit requirement. Id. at 998.

On appeal, the Ninth Circuit affirmed the district court’s order that the CWA applied, holding that the CWA regulates point source discharges to groundwater if the groundwater is hydrologically connected to a surface water and pollutants can travel through the groundwater to that surface water. Hawai’i Wildlife Fund v. County of Maui, 886 F.3d 737 (9th Cir. 2018). In explaining its holding, the Ninth Circuit reasoned that “(1) the County discharged pollutants from a point source, (2) the pollutants are fairly traceable from the point source to a navigable water such that the discharge is the functional equivalent of a discharge into the navigable water, and (3) the pollutant levels reaching the navigable water are more than de minimis.” Id. at 749.

Supreme Court weighs in

The Supreme Court granted certiorari and heard arguments in November 2019. Petitioner County of Maui and the Solicitor General contended that a CWA-covered point source must deliver pollutants directly to the surface waters—the existence of any nonpoint source intermediary (i.e., groundwater) renders the act inapplicable. The Respondent environmental groups advocated the Ninth Circuit’s analysis—permitting is required if a pollutant is merely fairly traceable to a point source, regardless of the distance and media through which it traveled.

The Court found that the arguments of both parties were “too extreme” and adopted a compromise—a permit is required when there is (1) a direct discharge from a point source into a navigable water, or (2) “the functional equivalent of a direct discharge.” Id. at 15. In so holding, the Court attempted to serve Congress’ goal of regulating identifiable sources of pollutants to navigable waters while also preserving State regulatory authority over land and groundwater. Whether the Court’s decision will actually do so, and its practical impact on the regulated community, will largely depend on future decisions and guidance by courts and the United States Environmental Protection Agency (EPA). In its decision, the Court recognized that many factors would be relevant in determining whether a discharge is the functional equivalent of a direct discharge, but largely left the development and application of such factors to future cases.

The Court did offer several guiding criteria on what constitutes a “functional equivalent.” It noted that, in most instances, transit time and distance traveled would be the most important factors. For example, the Court offered that a permit would be required where a pipe emits pollutants that travel a few feet through groundwater or over land to navigable waters. Conversely, the permit requirements would not apply if the pollutants traveled 50 miles through groundwater, mixed with other materials, and reached navigable waters many years later. In determining the in-between cases, the Court pointed to factors such as the nature of the material through which the pollutant travels, the extent to which the pollutant is diluted or chemically changed, the relative amount/volume of pollutant entering navigable waters, the manner by or area in which the pollutant enters the navigable waters, and the degree to which the pollution has maintained its specific identity. County of Maui, 590 U.S. __ , at 15-16.

Potential implications for dischargers

The Court answered the highly-anticipated question of whether the CWA can regulate discharges to navigable waters through groundwater with a direct, but tentative, “yes.” The circumstances under which a discharge to groundwater will be deemed the functional equivalent of a direct discharge are left somewhat ambiguous.

Under the new “functional equivalent” standard, discharges from point sources that flow through groundwater to navigable waters may now require an NPDES permit. In determining whether a permit may be required, facilities should consider the Court’s guiding criteria, including:

  1. The distance between the discharge and any river, stream, creek, lake, other surface water;

  2. Whether any nearby surface water falls within EPA’s jurisdiction under the CWA (i.e. whether it is a navigable water);

  3. The length of time between discharge to groundwater and entry of pollutants to surface water;

  4. The volume of the effluent or material discharged;

  5. The nature of the material through which the discharge travels;

  6. Whether the discharged material or effluent mixes with other materials before it reaches surface water;

  7. Whether the discharged material or effluent is diluted or chemically changed after discharge; and

  8. Whether the discharged material or effluent maintains any unique characteristics or identity after discharge.

Developing a system to permit indirect discharges also poses numerous logistical obstacles. For example, how are effluent limitations to be developed and implemented? How and where is effluent to be measured? How can regulators reliably determine the source(s) of such pollutants? Moreover, recognizing CWA jurisdiction over such discharges may threaten the finality of remedial actions commenced under state law and opens the door for more frequent citizen suits. We can expect that these and many other questions will arise in the coming months and years. In evaluating compliance with the CWA and potential NPDES permitting requirements, environmental consultants, practitioners, industry and other regulated entities should carefully consider and evaluate potential discharges to groundwater, as such discharges may now trigger CWA’s permitting requirements and closer regulatory scrutiny.

If you have questions regarding this article, environmental compliance, or environmental enforcement actions generally, please contact Sara Chamberlain or Paul Sonderegger in Thompson Coburn’s environmental practice area.