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Discharges to groundwater may require NPDES permits

January 14, 2025
Discharges to groundwater may require NPDES permits

Does your facility include features designed to discharge water into the ground, and does this water potentially contain pollutants? Or, are there features at your facility from which water containing pollutants may seep, leak, or infiltrate into the ground? If you answered yes to either question, it is important to understand whether your facility has a discharge through groundwater to a surface water that could be considered the “functional equivalent of a direct discharge” and thus require a National Pollutant Discharge Elimination System (NPDES) permit under Clean Water Act (CWA) Section 402.

Background

The April 2020 Supreme Court of the United States (SCOTUS) decision in County of Maui v. Hawaii Wildlife Fund, 140 U.S. 1462 (Maui decision) held that an NPDES permit is required “when there is a direct discharge from a point source into navigable waters or when there is the functional equivalent of a direct discharge.” Specifically, the Maui decision determined that underground injection wells at a wastewater treatment plant on the island of Maui, Hawaii, which discharged wastewater to groundwater that travels to the Pacific Ocean, needed an NPDES permit because the discharge is the functional equivalent of a direct discharge of pollutants to a water of the United States (WOTUS) (Pacific Ocean). (Note that “navigable water” and “water of the United States” are regulatory synonyms representing a subset of surface waters as defined in 40 CFR 120.2.)

In November 2023, the EPA released draft guidance to provide additional permitting considerations and direction for the implementation of the Maui decision in the NPDES permit program. The EPA’s draft guidance applies to point-source discharges that reach a WOTUS via groundwater or other subsurface flow. The EPA held a comment period for the draft guidance in November and December 2023. The next steps for this guidance are unclear given the January 2025 presidential transition.

Regardless of whether EPA guidance is in effect, a functional equivalent of a direct discharge through groundwater to a WOTUS requires an NPDES permit under CWA Section 402. State NPDES authorities have begun to add, and are anticipated to continue adding, related requirements to NPDES permits.

Why does this matter?

Prior to the Maui decision, case law was divided on whether the CWA governed discharges into groundwater that is hydrologically connected to a WOTUS. The Maui decision was the first at the SCOTUS level to clarify that the scope of the NPDES permitting program includes some discharges through groundwater to surface waters.

As a result, facilities with discharges to groundwater may need to conduct functional equivalent evaluations (evaluating whether they are the functional equivalent of direct discharges to WOTUS) to determine if NPDES permits are needed. Features that may discharge water containing pollutants to groundwater (intentionally or due to seepage, leakage, or infiltration) include:

  • Wastewater ponds, stormwater ponds, and infiltration basins

  • Landfills

  • Septic systems and other groundwater injections

  • Sprayfield or land application sites

  • Tailings basins, waste rock stockpiles, and flooded mine pits

  • Coal combustion residual impoundments

  • Leaking tanks, pipes, etc.

  • Subsurface contamination remaining in place

If a functional equivalent of a direct discharge is determined to be present, it will need to be permitted.

When is a functional equivalent evaluation needed?

Should your facility conduct a functional equivalent evaluation? Refer to the flowchart below to help determine if an evaluation may be needed given your situation.

Flowchart to help determine whether a functional equivalent evaluation may be needed.

What does a functional equivalent evaluation consider?

The Maui decision stated that many factors may be relevant in determining whether a particular discharge is the functional equivalent of a direct discharge and outlined seven example functional equivalent determination factors, as shown in the figure below.

If an EPA guidance document is finalized, it may include additional considerations to be incorporated into a functional equivalent evaluation.
 

Graphic explaining the functional equivalent of a direct discharge and determination factors
 

What do we know?

Although a final EPA guidance document is still pending, implementation of functional equivalent-related requirements is already in motion. Here’s what we know:

  • State NPDES authorities have begun to add functional equivalent-related requirements to NPDES permits. For example, both Minnesota and Montana’s delegated NPDES authorities have added requirements for dischargers to complete functional equivalent evaluations.

  • The EPA has provided technical assistance to at least one state NPDES authority to consider in deciding whether an NPDES permit is required for a particular instance of seepage to groundwater from a facility.

  • The EPA referenced the Maui decision in its new effluent limitation guidelines (ELGs) for coal-fired power plants. Learn more about this rule on our Insights blog.

Which cases have already tested the Maui decision?

Several cases have already tested the Maui decision with varying results, as described below:

  • Peconic Baykeeper, Inc. v. Harvey (No. 13-cv-6261, 2021 WL 4755623) found that septic tank discharge that reaches groundwater and surrounding navigable waters was not the functional equivalent of a direct discharge. Although time and distance indicate a functional equivalent of a direct discharge, the other factors in the evaluation suggest it was not.

  • Black Warrior River-Keeper, Inc. v. Drummond Company, Inc. (579 F.Supp.3d 1310, N.D. Alabama, Jan. 12, 2022) found that discharge from a mining waste pile that traveled via groundwater to the Locust Fork of the Black Warrior River in approximately 1.5 to 14.6 days was the functional equivalent of a direct discharge and that time and distance were the most important factors in making the determination.

  • Conservation Law Found., Inc. v. Town of Barnstable (615 F.Supp.3d 14, D. Mass., July 20, 2022) found that wastewater discharged to sand beds and ultimately transported via groundwater to the Lewis Bay Water system was not the functional equivalent of a direct discharge primarily because the estimated travel distance of 1.5 years and travel time of 21 years were too long.

  • Stone v. High Mountain Mining Co., LLC (No. 22-1340, 10th Cir. 2024) found that seepage to groundwater from ponds at a gold mine that are upgradient and less than 100 feet away from the Middle Fork River was not the functional equivalent of a direct discharge because the other factors considered in the Maui decision, besides transit time and location, did not show sufficient evidence of CWA violations.

What are we tracking?

Barr’s permitting experts are continuing to track developments related to this guidance, including:

  • What will be the fate of the EPA’s November 2023 draft guidance?

  • How will individual state NPDES permitting authorities incorporate functional equivalent-related requirements into NPDES permits?

  • How will the EPA and state NPDES permitting authorities handle potential liability when an evaluation indicates that a functional equivalent discharge is present? For example, the EPA’s November 2023 draft guidance notes that “if the discharge is the functional equivalent of a direct discharge to a WOTUS, the operator must obtain permit coverage prior to discharging pollutants (unless the operator eliminates the discharges). If the operator does not seek permit coverage for a functional equivalent discharge, the operator may be subject to administrative or judicial enforcement proceedings and associated liability under the CWA (including civil and criminal penalties).”

How can we help?

Functional equivalent evaluations and next steps regarding functionally equivalent discharge require collaboration among multiple service areas. For over 35 years, Barr has supported clients with these services, including water permitting and compliance, hydrogeology, wastewater treatment, and engineering design (e.g., lined facilities, tailings storage, water management). Contact our team with questions regarding the Maui decision, functional equivalent evaluations, or NPDES permitting.

About the authors

Jennifer Fleming, senior environmental engineer, assists clients with water-focused aspects of environmental review, permitting, and regulatory compliance. Her areas of expertise include NPDES wastewater and stormwater permitting and compliance, environmental regulatory reviews, and regulatory agency negotiations. Jennifer leverages her technical expertise to assist clients with developing and implementing facility-specific solutions to their permitting and compliance challenges. Her work frequently includes providing water regulatory expertise to projects that involve interconnection between surface water and groundwater, water management, wastewater treatment, and engineering design.

Jeré Mohr, vice president and senior hydrogeologist, has over 20 years of experience applying quantitative analysis of groundwater flow and solute transport to a variety of projects for industrial clients. His work focuses on design and management of subsurface investigations to characterize geology and hydrogeology and development of numerical groundwater-flow and solute-transport models. He is experienced with analysis and interpretation of complex water resources datasets, and with communicating technical information to regulatory agencies and other stakeholders.

Kate Sinner, environmental engineer, works with industrial and municipal clients to navigate permitting and compliance challenges, particularly those related to NPDES, in multiple states and EPA regions. Her project work has included permit applications, discharge feasibility studies, mixing zone studies, and compliance plans.

Becca Vermace, environmental engineer, helps industrial and municipal clients comply with drinking water and wastewater permit limits and achieve water quality goals by conducting feasibility studies and designing system retrofits. Her industrial wastewater experience spans a wide range of industries, including manufacturing, mining, agricultural, and refining, and includes projects focused on removing nutrients and PFAS from drinking water, wastewater, and stormwater.

Tags:

Water permitting NPDES Clean Water Act Direct Discharge CWA National Pollutant Discharge Elimination System Section 402 Functional Equivalent Point Source County of Maui v. Hawaii Wildlife Fund

 

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Jennifer Fleming
Senior Environmental Engineer

 

Jeré Mohr headshot
Jeré Mohr
Vice President, Senior Hydrogeologist

 

Kate Sinner headshot
Kate Sinner
Environmental Engineer

 

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Becca Vermace
Environmental Engineer
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