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National Pollutant Discharge Elimination System (NPDES)

Releases from a Point Source to Groundwater

Applying the Supreme Court’s County of Maui v. Hawaii Wildlife Fund Decision in the Clean Water Act Section 402 National Pollutant Discharge Elimination System (NPDES) Permit Program

On January 14, 2021, EPA issued guidance that clarifies how the Supreme Court’s County of Maui v. Hawaii Wildlife Fund decision should be applied under the NPDES permit program. This guidance will help clarify when a NPDES permit is necessary under the Clean Water Act.

In its decision, the Supreme Court held that a NPDES permit is required for a discharge of pollutants from a point source that reaches “waters of the United States” after traveling through groundwater if that discharge is the “functional equivalent of a direct discharge from the point source into navigable waters.”

EPA’s guidance places the ‘functional equivalent’ analysis into context within the agency’s NPDES permit program. The guidance reiterates the threshold conditions for triggering the requirement for a NPDES permit—an actual discharge of pollutants from a point source to a water of the United States. The guidance also explains that the design and performance of the system or facility from which the pollutant is released is an additional factor that should be considered. This action will provide guidance to assist the regulated community and permit authorities with incorporating the Supreme Court’s direction in Maui into existing Clean Water Act NPDES permitting programs and authorized state programs. 

EPA solicited public comments on the draft guidance for thirty days, beginning on December 10, 2020. EPA established an official public docket for receiving comments under Docket ID No. EPA–HQ–OW–2020–0673 which is accessible electronically at Regulations. gov ( that will also contain copies of an associated Federal Register notice. EPA has developed a responsiveness summary to address comments received, and it is available in the docket for this action.

Links to the pre-publication Federal Register notice, the guidance memorandum, and the Supreme Court Decision in Maui are below.