On December 10, 2020, the Environmental Protection Agency (“EPA”) published a draft guidance in the Federal Register clarifying how the agency would interpret the Supreme Court of the United States’ decision in Cty. of Maui v. Hawaii Wildlife Fund, 140 S. Ct. 1462 (2020). The case, which was decided on April 23, 2020 concerned whether discharges of pollutants which traveled through groundwater to enter a water of the United States fell under the jurisdiction of the Clean Water Act (“CWA”). The Court concluded that such discharges would fall under CWA jurisdiction, but only when the discharge served as the “functional equivalent” of a direct discharge. The draft guidance document issued by EPA is aimed at clarifying when a discharge into groundwater might be considered the functional equivalent of a direct discharge and therefore fall under CWA jurisdiction.


The CWA is the federal statute regulating the addition of pollutants into waters of the United States. One of the main tools employed by the CWA to regulate pollution is its permitting program. It is a violation of the CWA to make “any addition of any pollutant to navigable waters from any point source” unless the person doing so has a valid National Pollution Discharge Elimination System (“NPDES”) permit. Traditionally, only those discharges where the pollutant left the point source and directly entered a navigable water have required a NPDES permit. However, some have argued that the CWA should be interpreted to include the “conduit theory.” Supporters of the conduit theory argue that the NPDES permitting program should be expanded to cover discharges of pollutants into groundwater – which is not protected under the CWA – where the groundwater serves as a conduit to carry the pollutant to a navigable water.

The Cty. of Maui case was originally filed in 2012 against the County of Maui over discharges of pollutants made from a wastewater facility operated by the county. Pollutants at the wastewater facility were discharged from wells into groundwater through which the pollutants traveled to reach the Pacific Ocean. The discharges were made without a NPDES permit because groundwater is not protected under the CWA. However, the Hawaii Wildlife Fund argued that the CWA should apply where discharged pollutants traveled through groundwater to reach a navigable water. The United States Supreme Court ultimately sided with the Hawaii Wildlife Fund, concluding that when a discharge into groundwater is the “functional equivalent” of a direct discharge, a NPDES permit would be required. For more information on the decision, see here.

Although the Supreme Court did not specify exactly when a discharge into groundwater would be considered the functional equivalent of a direct discharge, it did provide a series of factors to consider when determining whether a discharge into groundwater would require a NPDES permit. In its opinion, the Court stated that EPA could provide further administrative guidance on which discharges into groundwater would be considered functionally equivalent.

Draft Guidance from EPA

In response to the Supreme Court’s decision, EPA has released a draft guidance document outlining how the agency will determine whether a discharge of pollutants into groundwater that transports the pollutants into a navigable water requires a NPDES permit. At the outset, EPA notes that the Cty. of Maui decision did not change the CWA or the NPDES program, and that EPA does not have the ability to change the NPDES program through a guidance document. Instead, EPA states that Cty. of Maui “identified an additional analysis that should be conducted in certain factual scenarios to determine whether an NPDES permit is required.” The goal of EPA’s guidance document is to put the functional equivalent analysis into context with the current NPDES framework in order to help regulators and the regulated understand when and how to apply a “functional equivalent” analysis.

According to EPA, the Supreme Court’s decision maintained certain “threshold conditions” that need to be met before an obligation to have a NPDES permit is triggered. First, there must be an actual discharge of a pollutant to a navigable water, and second, that discharge must be from a point source. Once those threshold requirements have been met, the next step is to determine whether there are any indications that there may be a discharge of pollutants into groundwater that reach waters protected under the CWA. If there are indications that such a discharge is occurring, EPA considering “whether a conducting a technical analysis would be prudent.” Examples of such indications include “a discharge of highly mobile pollutants from a point source directly into sandy soils, or in an area with shallow groundwater in close proximity” to a navigable water.

If there is an indication that a discharge into groundwater could be the functional equivalent of a direct discharge, then a technical analysis may take place. Either the discharger or EPA will conduct the evaluation depending on whether the evaluation is part of a NPDES permit application or an enforcement action. Importantly, EPA notes that a “mere allegation” that a point source discharge of pollutants may be traveling through groundwater to reach a navigable water will not be sufficient to trigger the need for a NPDES permit. Additionally, a demonstration that pollutants discharged from a point source have reached a navigable water via groundwater is also not enough to trigger the requirement for a NPDES permit. Instead, a NPDES permit will only be required for such a discharge if a “functional equivalent” analysis shows that a permit is needed.

A “functional equivalent” analysis requires applying the factors provided by the Supreme Court that may be used to determine whether a discharge of pollutants into groundwater is the functional equivalent of a direct discharge. Those factors are: (1) transit time, (2) distance traveled, (3) the nature of the material through which the pollutant travels, (4) the extent to which the pollutant is diluted or chemically changed as it travels, (5) the amount of pollutant entering the navigable waters relative to the amount of the pollutant that leaves the point source, (6) the manner by or area in which the pollutant enters the navigable waters, and (7) the degree to which the pollution (at that point) has maintained its specific identity. Those factors were outlined in the Cty. of Maui decision and were used by the Court to decide that case. Additionally, EPA has identified a factor of its own based on the authority granted to EPA in Cty. of Maui case: the design and performance of the system or facility from which the pollutant is released. According to EPA, “the design and performance of the system or facility from which the pollutant is released can inform the scope and extent of the “functional equivalent” analysis[.]”


The draft guidance document from EPA is aimed at clarifying when a “functional equivalent” analysis should be applied to discharges of pollutants into groundwater. In the document, EPA makes it clear that the intention is not to drastically increase the number of NPDES permits required following the Cty. of Maui decision. Instead, EPA states that the “functional equivalent” analysis should only be applied when there are clear indications that pollutants discharge from a point source into groundwater may be reaching a navigable water, and of those discharges only a fraction will require permits following analysis. Specifically, EPA notes that if the composition of a discharged pollutant has sufficient broken down or altered upon reaching a navigable water, then a permit will likely not be required.

The guidance document is still in its draft stage. EPA is taking comments from the public until January 11, 2021, after which a final draft of the guidance document will be released. However, the incoming Biden administration will take office January 20, 2021, which may impact how EPA approaches the Cty. of Maui decision.


To read the draft guidance document, click here.

To submit comments to EPA, click here.

To read the decision in Cty. of Maui, click here.

To read the text of the CWA, click here.

For additional National Agricultural Law Center resources on the CWA, click here.