On November 20, with no fanfare at all, not even a press release, U.S. Environmental Protection Agency (EPA) issued its Draft Guidance: Applying the Supreme Court’s County of Maui v. Hawaii Wildlife Fund Decision in the Clean Water Act Section 402 National Pollutant Discharge Elimination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 Permit Program to Discharges Through Groundwater. This draft guidance is the agency’s second effort to guide implementation of the U.S. Supreme Court’s 2020 decision, which extends applicability of the National Pollutant Discharge Elimination System (NPDES) permitting program to include the “functional equivalent” of point source discharges of pollutants to waters of the U.S.

Clean Water Act Permitting and the Maui Decision

The NPDES permit program, created by the Clean Water Act, requires a permit for any point source discharge of a pollutant to a water of the U.S. Point source discharges are those from a discrete conveyance, “including but not limited to any pipe, ditch, channel, tunnel, conduit…” but they do not include nonpoint or diffuse discharges like surface water runoff. The NPDES permit program protects surface water quality from industrial, municipal, and other dischargers, with an aim to ensure that EPA-approved water quality standards are maintained. Most NPDES permits contain effluent limitations, which limit the concentration or mass of a pollutant that may be discharged from a facility; while other NPDES permits rely on best management practices to achieve the same end.

In April 2020, the U.S. Supreme Court considered whether a point source discharge that travels through groundwater before reaching a water of the U.S. may be subject to the NPDES permit program. In the Maui case, the County of Maui was injecting pollutants into a deep well in accordance with a Safe Drinking Water Act Underground Injection Control permit, but a portion of those pollutants traveled through the subsurface and ultimately discharged into the Pacific Ocean, a water of the U.S. The Court concluded that some discharges through groundwater are subject to the NPDES permit program and created a new multifactor test to evaluate when a discharge to groundwater is the “functional equivalent” of a discharge to a water of the U.S.

The Court noted that “there are too many potentially relevant factors” to be more specific in its opinion, but did enumerate “just some of the factors that may prove relevant (depending upon the circumstances of a particular case): (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, (7) the degree to which the pollution (at that point) has maintained its specific identity.” 140 S. Ct. 1462, 1477 (2020). The Court specifically noted that, “Time and distance will be the most important factors in most cases, but not necessarily every case.” Id.

EPA’s 2021 Maui Guidance

In response to the Court’s Maui decision, EPA issued draft Maui guidance for public comment in late 2020, and issued a final Guidance Memorandum in January 2021. EPA’s 2021 Maui guidance reiterated three basic tenants of Clean Water Act jurisprudence that were unaffected by the Court’s decision: first, that a discharge of pollutants to a water of the U.S. must occur to trigger the NPDES permit requirement; second, that the pollutant must be discharged from a point source to trigger the NPDES permit requirement; and third, only a subset of discharges through groundwater that reach a water of the U.S. are “functional equivalent” discharges under the Court’s decision. The 2021 Maui guidance also identified an additional factor that the agency considered relevant to the inquiry: the design and performance of the facility from which the pollutant was discharged. The 2021 guidance explained that the system’s design and performance “can affect or inform all seven factors in Maui” including transit time, distance traveled, chemical changes or dilution, and chemical concentrations when entering the water of the U.S.

In September 2021, EPA rescinded its 2021 Maui guidance document citing two primary reasons. First, EPA asserted that the system design and performance factor identified in the 2021 Maui guidance “is not consistent with the Clean Water Act or the Court’s decision” because “the additional factor introduces an element of intent that is not reflected in or consistent with the County of Maui decision.” EPA also stated that its own 2021 guidance was “issued without proper deliberation within EPA or with our federal partners.”

EPA’s 2023 Draft Maui Guidance

More than two years after rescinding its original Maui guidance, EPA has finally issued a new draft guidance document. The draft guidance first acknowledges that the Court’s Maui decision concluded that some discharges through groundwater may be subject to the NPDES permit program, but there is no bright line rule, and the analysis will be very fact-specific.

Consistent with the 2021 Maui guidance, the 2023 draft guidance reiterates that to trigger the NPDES permit requirement, an operator must first identify a discharge of pollutants that reaches a water of the U.S. If a discharge through groundwater actually reaches a water of the U.S., the operator must then determine if that discharge could be considered a “functional equivalent” of a direct discharge to surface waters. In other words, while all point source discharges to surface waters of the U.S. require a NPDES permit, only a subset of discharges through groundwater that reach a water of the U.S. — those that are a functional equivalent of a direct discharge — trigger the NPDES permit requirement.

The 2023 draft guidance then walks through an “overall approach” to conducting a functional equivalent analysis. Here, the agency notes that the Court in Maui listed seven factors as illustrative, but other factors may be relevant. In a missed opportunity to provide additional guidance to state regulators and permittees, the draft guidance does not offer any additional factors that may be relevant to such an analysis.

The draft guidance does, however, offer a new twist on the Clean Water Act-defined term, “pollutant.” While the Clean Water Act prohibits the discharge of pollutants, the draft guidance states that it may be helpful “in some situations” to evaluate “constituents of those pollutants” rather than the pollutants themselves. The draft guidance does not provide any examples of pollutants versus indicator constituents, but states that finding a functional equivalent of a single “indicator constituent” would be sufficient to require a NPDES permit. By contrast, finding no functional equivalent of a single “indicator constituent” would not rule out the need for a NPDES permit. It will be interesting to see how stakeholders respond to this new twist on a statutorily defined term, especially since the Court in Maui was very focused on the pollutant itself. Indeed, Maui factors 4, 5, 6, and 7 all focus on the character of the pollutant — the extent of its dilution or chemical change as it travels, the amount entering the surface water relative to the amount in the initial point source discharge, and the degree to which the pollution has maintained its specific identity — not whether the pollutant can be reasonably inferred to have been discharged because of some undefined indicator constituents.

For applicants seeking NPDES permit coverage for a discharge through groundwater, the draft guidance provides a recommended list of information that may be useful for the permit writer to consider. To avoid an allegation that EPA would require state permit writers to request or consider this information, the draft guidance is careful to state that it “does not mean to suggest in any way that this information is needed in any particular case” but that the permitting authority will need to determine what, if any, information it needs to authorize a discharge through groundwater under the NPDES program.

Interestingly, the list of recommended information includes a “description of in-situ processes such as sorption, biological uptake, or microbial transformation that may reduce the pollutant mass that reaches water(s) of the United States” and “[a]ny treatment technologies planning to be used” including any chemicals or additives. These information items sound an awful lot like the system design and performance factor recommended in EPA’s 2021 Maui guidance that the agency later rescinded claiming such consideration would be inconsistent with the Clean Water Act and the Maui decision. With the benefit of more than two years of additional deliberation, it appears that EPA now believes understanding whether a system is designed to treat pollutants before they are discharged is not only a lawful consideration under the Clean Water Act and the NPDES program, but a relevant aspect of the functional equivalent analysis.

Lastly, the draft guidance identifies two factors that EPA believes are not relevant to a functional equivalent analysis: whether a discharge is intentional, and the existence of a state groundwater protection program. The former is uncontroversial, as the Clean Water Act has long been construed as a strict liability statute. The latter may be controversial in some states, and it may be shortsighted for EPA to take such a hard-line position on state groundwater protection programs. Indeed, it might be worthwhile for EPA to take a case-by-case approach to state groundwater protection programs, especially in cases where they address the groundwater-surface water interface, where they require groundwater protections that also meet surface water quality standards, or where the state groundwater programs are currently or could be modified to work in conjunction with state-administered NPDES programs.

The draft guidance was published in the Federal Register on November 27, and is available for public comment until December 27.