EPA Draft Guidance Released on NPDES Permitting Applicability to Groundwater Discharges

On November 20, 2023, the Environmental Protection Agency (EPA) issued a draft guidance document on National Pollutant Discharge Elimination System (NPDES) permitting applicability for groundwater discharges based on the Supreme Court’s decision in Maui v. Hawaii Wildlife Fund. In the draft guidance, EPA describes the functional equivalent standard applied in the Maui decision and the information which may be required to obtain an NPDES permit for groundwater discharges. Though the draft guidance outlines seven factors which should be considered in determining whether a groundwater discharge is functionally equivalent to a direct discharge, the guidance explains that site-specific features will impact what should be considered to make this determination. The deadline for public comment on the draft guidance document is December 27, 2023.

How did we get here?

In April 2020, the Supreme Court issued its opinion in County of Maui v. Hawaii Wildlife Fund on whether a wastewater treatment plant in Maui, HI needed an NPDES permit for discharging pollutants into underground injection wells which traveled through groundwater to the Pacific Ocean, a water of the United States (WOTUS). The Supreme Court held that NPDES authorization is required for discharges of pollutants from point sources that travel through groundwater to WOTUS if the addition of pollutants is the functional equivalent of a direct discharge. In the decision, the Court listed seven (7) factors which may be relevant in determining whether a discharge is the functional equivalent of a direct discharge and requires an NPDES permit:

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 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 pollutant at the point has maintained its specific identity

The Supreme Court sent the case back to the district court with this test, and the district court ultimately ruled that the County of Maui was required to obtain an NPDES permit for its underground injection activities.

Draft Guidance:

In the draft guidance, EPA provides considerations for determining which discharges through groundwater may require coverage under an NPDES permit:

1. Owners and operators should evaluate whether their discharges reach WOTUS.
2. If so, owners and operators should evaluate whether those discharges are the functional equivalent of direct discharges which require NPDES permits.

Functional Equivalent Analysis

The EPA draft guidance provides principles for owners and operators to conduct a functional equivalent analysis:

• The discharge of pollutants from groundwater to surface waters is highly dependent on site-specific features as described in the Supreme Court decision. Though the Supreme Court decision identified time and distance as the most important factors in the functional equivalent analysis, the weight of the relevant factors is at the discretion of EPA and is dependent on site-specific considerations. The Supreme Court nor EPA provide specific guidance on what times and distances would make a discharge functionally equivalent to a direct discharge, however, they state that a discharge which is a short distance from a WOTUS that takes a short time to reach a WOTUS is likely a functional equivalent of a direct discharge. Conversely, a discharge with a long distance (e.g. 50 miles) from a WOTUS that takes a long time (e.g. 100 years) to reach a WOTUS might not be a functional equivalent of a direct discharge. The guidance also provides additional examples of what may be considered a functional equivalent of a direct discharge:
  • If a pollutant plume has minimal dispersion before entering a WOTUS
  • A discharge through a subsurface comprised of porous materials
  • A relatively higher mass or concentration of pollutants reaching a WOTUS relative to the mass or concentration of pollutants leaving the point source
• The list of factors identified by the Supreme Court for the functional equivalent analysis are some of the factors that may be relevant, but additional factors may be relevant depending on the site.
• The functional equivalent analysis may not require considering all factors laid out by the Supreme Court depending on the circumstances.
• A functional equivalent analysis may be performed using one constituent pollutant where that pollutant is a reasonable indicator for other constituent pollutants.

The EPA guidance documents also clarifies factors which should not be considered as a part of the functional equivalent analysis:

1. Intent of a discharger
2. Whether the state has a groundwater protection program

Permit Application Recommended Requirements

EPA suggests that the following information may be required when submitting a permit application for a groundwater discharge subject to NPDES permitting:

• Discharge locations
• Transit time
• Distance travelled
• Flow characteristics
• Shallow subsurface geology and hydrology characterization
• Description of pollutant-specific dynamics along the groundwater flow path
• Treatment technologies
• Effluent characteristics
• An explanation of the permittees functional equivalent of a direct discharge analysis

Why It Matters:

The Maui decision and EPA draft guidance may directly impact facilities which discharge to groundwater. As a result of the Maui decision and the newly released EPA draft guidance, owners and operators of facilities are prompted to review their groundwater discharge applicability to NPDES permitting to ensure compliance with federal and state regulations. This is especially critical for facilities that are close to WOTUS.

Facilities should conduct functional equivalent analysis for any groundwater discharges that may reach WOTUS. Additionally, owners and operators may need to reach out to their applicable agency for NPDES permitting for additional guidance or a decision on whether their discharge is the functional equivalent to a direct discharge due to the lack of clarity in the Maui decision and the EPA draft guidance.

For more information or for assistance, please contact Trinity Consultants at 800.229.6655.