Late last year, the Environmental Protection Agency (“EPA”) issued a draft guidance intended to assist regulated entities and permitting authorities in applying the U.S. Supreme Court’s decision in County of Maui, Hawaii v. Hawaii Wildlife Fund, concerning Clean Water Act (“CWA”) jurisdiction over discharges to groundwater. In that case, the Supreme Court held that the CWA requires a permit not only for direct discharges into navigable waters, but also for the “functional equivalent” of direct discharges. The Court then set forth seven non-exclusive factors to determine whether a groundwater discharge is “functionally equivalent” to a direct discharge and thus requires a permit.

EPA’s draft guidance analyzes this new test in the context of the National Pollutant Discharge Elimination System (“NPDES”) program and provides insight into how EPA currently interprets and intends to apply the Maui decision. The guidance begins by reiterating the threshold conditions that trigger the NPDES permit requirement: (1) there must be an actual discharge of a pollutant to waters of the United States; and (2) the discharge in question must originate from a point source. If these two conditions are satisfied, EPA recommends conducting the functional equivalence analysis.

As the Maui decision makes clear, various factors—including transit time and distance traveled—must be considered before making that determination. However, the guidance also clarifies that not all discharges to groundwater will meet the functional equivalence test, even if they ultimately reach a jurisdictional water. Put differently, although a discharge of pollutants from a point source is necessary to trigger the need for an NPDES permit, it’s not sufficient.

The draft guidance emphasizes that the Maui decision did not instruct NPDES permitting authorities to assume that discharges to groundwater in the vicinity of a jurisdictional water are the “functional equivalent” of direct discharges to that water, and EPA also points out that nothing in the Maui decision or the CWA more generally requires a facility owner or operator to prove the absence of a discharge. Similarly, the guidance states that “a mere allegation (i.e., without supporting evidence) that a point source discharge of pollutants is or may be reaching a water of the United States via groundwater is not sufficient to trigger the need for an NPDES permit.” The guidance recognizes that many groundwater discharges may never reach jurisdictional waters for a number of reasons, including characteristics of the pollutant itself and the nature of the subsurface aquifer and hydrogeology.

Thus, EPA recommends “considering whether conducting a technical analysis would be prudent” only where there are indications that a groundwater discharge is reaching waters of the United States. Such indications may include “discharge of highly mobile pollutants from a point source directly to sandy soils, or in an area with shallow groundwater in close proximity to a water of a United States.” If those indications are present, EPA suggests that regulated entities evaluate hydraulic conductivity based on various factors, including the soil type or porosity and hydraulic gradient through which the pollutant travels, depth to groundwater, groundwater flowpath (including distance and transit time over which the pollutant reaches the receiving water of the United States), or pollutant-specific dynamics along the groundwater flowpath.

EPA also identifies a new factor to consider in conducting a functional equivalent analysis—system design and performance. The guidance explains that examining the design and performance of the regulated entity’s system is an important and routine consideration for permitting agencies. EPA suggests that the design of the system can affect the composition and/or concentration of pollutants, the transit time of pollutants, the distance travelled by pollutants, and the amount of pollutant entering the water—and can therefore provide helpful insight into whether a discharge is the “functional equivalent” of a direct discharge.

Although the draft guidance provides some useful clues about how EPA currently views the Maui decision and its regulatory authority over groundwater discharges, its vague description of the relevant considerations may not be useful to facility owners looking for specific benchmarks or numerical values. That said, the guidance does make clear that EPA doesn’t intend to drastically increase the number of NPDES permits required following the Maui decision. Instead, EPA’s position seems to be that the functional equivalence test should be applied only where there are clear indications that pollutants discharged from a point source into groundwater may be reaching a navigable water.

Notably, the guidance is not binding, and it does not have the force and effect of law. It is therefore possible that under the Biden administration, the EPA will adopt a broader interpretation of the Maui decision and revise or retract the draft guidance altogether. The regulated community can take some comfort in EPA’s current position, but we recommend that owners and operators of facilities with discharges that may impact groundwater continue to track developments in EPA’s thinking on this issue, with the expectation that a Biden administration will favor a more expansive interpretation and application of the Maui decision than did the Trump administration.