NPDES Permits for Certain Point Source Discharges of Pollutants that Travel Through Groundwater to Surface Waters

Supreme Court Decision

In County of Maui v. Hawaii Wildlife Fund, the U.S. Supreme Court held that point source discharges to a water of the United States through groundwater require a National Pollutant Discharge Elimination System (NPDES) permit if the discharge is the “functional equivalent” of a direct discharge.

• 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 (pdf) (327.77 KB)

Draft Guidance

On November 27, 2023, EPA published a draft guidance for public comment titled: Applying the Supreme Court’s County of Maui v. Hawaii Wildlife Fund Decision in the Clean Water Act Section 402 National Pollutant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. The draft guidance describes the decision’s functional equivalent analysis and explains the types of information that should be used to determine which discharges through groundwater may require coverage under a NPDES permit.

• Draft Guidance: Applying the Supreme Court’s "County of Maui v. Hawaii Wildlife Fund" Decision in the Clean Water Act Section 402 National Pollutant Discharge Elimination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 (pdf) (285.28 KB)
• Federal Register Notice (pdf) (186.5 KB)
• For public comments on the draft guidance, see: Docket ID No. EPA–HQ–OW–2023–0551 (https://www.regulations.gov/docket/EPA-HQ-OW-2023-0551).

Frequently Asked Questions

These Frequently Asked Questions (FAQs) are intended to respond to stakeholder questions regarding the United States Supreme Court’s decision in County of Maui v. Hawaii Wildlife Fund, 140 S. Ct. 1462 (2020) (Maui). These FAQs are not intended, nor can they be relied upon, to create any rights enforceable by any party in litigation with the United States. The FAQs do not have the force and effect of law and are not meant to bind parties in any way. The general descriptions and recommendations provided herein may not apply to every situation based upon the particular circumstances at issue. EPA and other permitting authorities retain the discretion to adopt or recommend approaches on a case-by-case basis that differ from those described, as appropriate. (Note: The FAQs use the phrases “functional equivalent of a direct discharge,” “functional equivalent discharge,” and “functional equivalent” interchangeably. Each phrase refers to the “functional equivalent of a direct discharge” standard articulated in Maui.)

1. What is “Groundwater” in the context of Maui?
   As used in the draft guidance, the term “groundwater” encompasses all subsurface water, including water in the unsaturated zone above the groundwater table.

2. Must the discharge be from a point source?
   Yes. A discharge of pollutants must be from a point source to waters of the United States to require NPDES permit authorization. In Maui, the Supreme Court held that NPDES authorization is required for certain discharges of pollutants from point sources that travel through groundwater to surface waters and wetlands that are “waters of the United States.”

3. Must a permittee seek permit coverage prior to a functional equivalent discharge to a “water of the United States”?
   Yes. Point sources are required under the Clean Water Act (CWA) to seek authorization under the NPDES permitting program prior to discharging any pollutants to surface waters and wetlands that are “waters of the United States.” This longstanding principle also applies to functional equivalent discharges.

4. What about State-issued NPDES permits that authorize discharges to “state waters”?
   The Agency recognizes that many NPDES-authorized states use the term “state waters” or a similar term to designate which discharges must obtain permit coverage and that some states define state waters more broadly than “waters of the United States.” These FAQs address discharges of pollutants that travel through groundwater to surface waters and wetlands that are waters of the United States. If the ultimate destination of the discharge is a state water that is not also a water of the United States, the discharger should evaluate state law to determine whether any requirements apply to that discharge.

5. Are all releases of pollutants from a point source through groundwater to waters of the United States the functional equivalent of a direct discharge?
   No. Some releases from a point source through groundwater to waters of the United States require an NPDES permit, and some do not. Specifically, only discharges through groundwater that are the functional equivalent of a direct discharge require an NPDES permit.

6. Is the functional equivalent of a direct discharge determination site-specific?
   Yes. Whether a release from a point source that travels through groundwater before discharging to a water of the United States is the functional equivalent of a direct discharge depends on site-specific features.

7. What factors did the Court state may prove relevant in determining whether a discharge is the functional equivalent of a direct discharge?
   The Court stated that some of the factors that may prove relevant in determining whether a discharge is the functional equivalent of a direct discharge and requires an NPDES permit include, for example: “(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.”

8. Which factors did the Court identify as most important in most cases?
   Transit time and distance traveled.

9. Do all factors identified by the Court need to be considered in each case?
   No. Depending on the circumstances, the functional equivalent analysis may not require consideration of all, or even several of, the factors laid out by the Court.

10. Can factors other than those identified by the Court be considered?
    Yes. The list of factors identified by the Supreme Court is illustrative. As the Supreme Court noted, the seven factors identified in its opinion were just some of the factors that may prove relevant to determining whether a discharge is the functional equivalent of a direct discharge.

11. How should the relevant factors be weighed?
    The weighing of the relevant factors is highly dependent on case-specific considerations. While the Supreme Court identified time and distance as the most important factors in most cases, the Court left to the Agency’s discretion how to weigh the relevant factors.

12. Who is responsible, in the first instance, for determining whether a discharge through groundwater needs an NPDES permit?
    Operators of facilities with releases to groundwater should evaluate in the first instance whether those releases reach waters of the United States and, if so, whether they are the functional equivalent of direct discharges that require NPDES permits.

13. What about more complex scenarios that may require consideration of more factors? 
    In complex scenarios, to better understand pollutant transport and loadings to waters of the United States, a site-specific characterization by an appropriate professional may be helpful. Such an evaluation could include a dye tracer study, subsurface characterization, or modeling groundwater flow.

14. Should a permit applicant request to meet with the permitting authority to help identify the information that the permitting authority will need to review the functional equivalent analysis and to process the permit application?
    Yes. EPA recommends that the permit applicant request a meeting with the permitting authority early in the permitting process so that the permitting authority can identify the supplemental information it may ask the applicant to provide.

15. Is the functional equivalent analysis pollutant specific?
    Yes. A finding of a functional equivalent discharge for one pollutant in an effluent could demonstrate a functional equivalent discharge for other pollutants in an effluent that have the same fate and transport characteristics. Conversely, establishing a lack of functional equivalence for one or more pollutants does not necessarily demonstrate that the functional equivalent of a direct discharge does not exist for other pollutants in the effluent if the other pollutants have different fate and transport characteristics. Note that determining that the discharge of just one pollutant is the functional equivalent of a direct discharge would trigger the permitting requirement.

16. Is dilution that may occur in a receiving water body a factor that should be considered as part of a functional equivalent analysis?
    No. What happens to a pollutant after it enters the jurisdictional water is not part of the functional equivalent analysis.

17. In general, are stormwater control features (including green infrastructure), groundwater control recharge features, on-site disposal features, lagoon disposal features, and treated wastewater infiltration systems likely to have a functional equivalent discharge?
    No. In general, discharges through groundwater from stormwater control measures (including green infrastructure), groundwater recharge projects, and on-site disposal systems, commonly known as septic systems, that are properly designed, sited, installed, maintained, and appropriate for the pollutants they receive are unlikely to result in functionally equivalent discharges.   

18. Should an operator seeking a permit for a functional equivalent discharge use the current permit application forms? 
    Yes. Absent EPA or state permit application forms specific to discharges through groundwater, EPA recommends that a permit applicant with a discharge through groundwater that is the functional equivalent of a direct discharge submit a permit application using the existing form(s) that the permitting authority requires for the facility. Applicants for NPDES permits must provide information using the application form provided by the permitting authority.

19. If a permitting authority requests that supplemental information be submitted in addition to the information in the permit application, is the operator required to submit such information for the application to be considered complete?
    Yes. The NPDES regulations prohibit the permitting authority from issuing an individual permit until and unless a prospective discharger provides a “complete application which includes an application form and any supplemental information completed to their satisfaction.”

20. What types of supplemental information may be appropriate for the permitting authority to request?
    The supplemental information provided here for consideration includes discharge location(s), transit time, distance travelled, flow characteristics, shallow subsurface geology and hydrology characterization, description of pollutant-specific dynamics along the groundwater flow path, effluent characteristics, and an explanation of the permittee’s functional equivalent analysis. This information is illustrative of the range of information that may be available from multiple sources. This list does not mean to suggest in any way that this information is needed in any particular case; the permitting authority will need to determine what information is relevant to the discharge in question and may determine if it needs this information in its entirety, a subset of this information, none of the information, or any other additional information.

21. What should the permitting authority consider when requesting supplemental information?
    EPA recommends that permitting authorities should only request information that is reasonably necessary to inform the decision to issue a permit and the conditions and limitations that would be in the permit. The list of potentially relevant supplemental information described in Question 20 is provided for consideration. The permitting authority will need to determine what supplemental information is relevant to the discharge in question and may determine if it needs this supplemental information in its entirety, just a subset of it, none of the information, or any other additional written information. Permitting authorities can consider the feasibility and amount of time associated with the collection of quantitative data, and may consider estimates of pollutant discharge, as appropriate.

22. Since the functional equivalent analysis is case-specific, is it appropriate for permitting authorities to use general permits to authorize functional equivalent discharges?
    A general permit approach could be appropriate for permitting certain types of functional equivalent discharges and permitting authorities may consider such an approach.

23. Should intent be considered as part of the functional equivalent analysis?
    No. Intent is not a relevant factor when assessing whether a discharge is subject to the CWA, including a discharge through groundwater that is the functional equivalent of a direct discharge. Instead, the characteristics of the discharge are relevant to the functional equivalent analysis.

24. Should the existence of a state groundwater protection program be considered as part of the functional equivalent analysis?
    The existence of a state groundwater protection program does not preclude CWA liability for point source discharges through groundwater that are the functional equivalent of direct discharges; however, a state groundwater program and the measures an operator has taken in response to that program may be relevant to the functional equivalent analysis where such measures impact the nature of the release through groundwater to a water of the United States. In these cases, it is not the mere existence of a state groundwater program that is relevant to the functional equivalent analysis, but rather how the measures an operator has taken in response to that program and the impact of those measures on the nature of a particular discharge to surface waters.

25. Where can I find examples of permits for functional equivalent discharges?
    As examples become available, EPA plans to include them in the publicly available NPDES Permit Writer’s Clearinghouse.

26. If I have further questions for EPA about the Maui draft guidance, the FAQs, or a functional equivalent determination, who can I contact?
    Please see the Contact EPA about NPDES general information link. EPA recommends that operators should begin by contacting their NPDES permitting authority.