The Clean Water Act sometimes requires a permit for the indirect discharge of pollutants from a point source to navigable waters, but only when the discharge is the “functional equivalent” of a direct discharge, the Supreme Court held on April 23.  The Court’s 6-3 opinion in County of Maui v. Hawaii Wildlife Fund (No. 18-260) addresses a circuit split regarding whether indirect discharges to navigable water via groundwater are subject to the Act’s National Pollutant Discharge Elimination System (“NPDES”) permitting program, but it has implications for other types of indirect discharges as well.  Although the Court identified some factors that may help determine when a discharge is the functional equivalent of a direct discharge—especially the time and distance between the discharge of a pollutant from a point source and the pollutant’s arrival in navigable waters—its opinion is likely to create substantial uncertainty for the regulated community as the Environmental Protection Agency (“EPA”), litigants, and the courts attempt to apply the Court’s multi-factor test to a variety of factual scenarios.


The Clean Water Act prohibits “any addition of any pollutant to navigable waters … from any point source” without a permit.  There is no dispute that this language covers the discharge of a pollutant from a point source directly into covered waters.  The question in County of Maui was whether the statute reaches situations in which a pollutant is discharged from a point source but reaches navigable waters only after travelling through groundwater, which is not a point source.  Since the 1970s, the County of Maui has operated a wastewater treatment facility that pumps treated effluent into four underground injection wells, from which the effluent enters groundwater and travels about half a mile before reaching the Pacific Ocean.  In 2012, several environmental groups brought suit, arguing that Maui was discharging a pollutant into navigable waters without a permit.

The district court ruled that the facility required an NPDES permit, and the Ninth Circuit affirmed in 2018, holding that a permit is required when 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.  That same year, however, the Fourth Circuit held that such discharges are regulated only when a “direct hydrological connection” exists between the point source and the waters, while the Sixth Circuit held that the Act does not cover discharges through groundwater at all.  The EPA, meanwhile, has taken contradictory positions on the issue.

Supreme Court Holding

The Supreme Court rejected both the Ninth Circuit’s “fairly traceable” test and the EPA’s current view that discharges via groundwater are entirely exempt, characterizing both as too extreme.  Instead, the Court held that requiring a permit for direct discharges and those that are the “functional equivalent” to direct discharges best captures Congress’ intent to regulate identifiable pollutants entering navigable waters without undermining the State’s “longstanding regulatory authority over land and groundwater” and its regulation of non-point sources.

The Court acknowledged that this is not a precise standard, but advised that “time and distance will be the most important factors in most cases.”  Other, non-exclusive factors that may be relevant include:

  • The nature of the material through which the pollutant travels;
  • The extent to which the pollutant is diluted or chemically changed in transit;
  • The amount of pollutant entering the navigable waters relative to the amount of pollutant leaving the point source;
  • The manner by or area in which the pollutant enters the navigable waters; and
  • The degree to which the pollution (at that point) has maintained its specific identity.

Given the fact-specific, flexible nature of this multi-factor test, which drew criticism from dissenting justices Alito, Thomas and Gorsuch, it is unclear what discharges will now require permits, and we can expect more litigation as citizen suits and enforcement actions make their way through the courts.

*This alert is provided for information purposes only and does not constitute legal advice and is not intended to form an attorney client relationship.  Please contact your Sheppard Mullin attorney contact for additional information.*