The U.S. Environmental Protection Agency (EPA) has issued a Draft Guidance Memorandum following the recent U.S. Supreme Court decision in County of Maui v. Hawaii Wildlife Fund.  139 S.Ct. 1164 (2019).  This Guidance Memo attempts to give regulators and source owners additional clarity as to when the functional equivalent test should be applied. 

County of Maui, which was decided in April 2020, determined a discharge to groundwater could be the “functional equivalent” of a discharge into navigable waters where the discharge’s migration to navigable waters is clearly ascertainable.  The decision created concerns that any discharge making its way to navigable waters will require a permit regardless of the source or the source owner’s intentions. 

In addition to the seven factors outlined by the Supreme Court, which are not exhaustive, EPA suggested system design and performance should be considered to determine whether a particular discharge is a “functional equivalent.”  The Guidance Memo stated facility design may impact all seven County of Maui factors, since some systems are designed to promote dilution, adsorption or dispersion of the pollutant with the intent to chemically change the pollutant and the amount of pollutant that would enter navigable waters relative to the amount that leaves the point source. 

Examples include septic systems, settling ponds, runoff management systems, infiltration or evaporation systems, and reuse, recycling or groundwater recharge systems.  The EPA stated it may be less likely that an NPDES permit would be required for these types of systems either because the pollutants do not reach a navigable water or because the discharge is not the functional equivalent of a direct discharge to a navigable water of the United States.  This new test is not a law and is not legally challengeable.  Regulators and source owners should monitor the application of this new test and whether it survives with the change in administrations in 2021.