New NPDES Guidance on Discharges to Groundwater

Posted on 11/27/2023 by Roger Marks

US EPA recently released a draft copy of new guidance intended to help the regulated community comply with NPDES permitting requirements for discharges of pollutants to groundwater.

The newly drafted guidance is meant to clarify when a NPDES permit is required to discharge pollutants to a water of the United States (WOTUS)—including some discharges that travel through groundwater before reaching a WOTUS.

New NPDES Guidance on Discharges to Groundwater

Why NPDES Guidance? Why Now?

The new NPDES draft guidance stems from a 2020 Supreme Court decision in the case County of Maui v. Hawaii Wildlife Fund. That legal fight centered on whether a wastewater treatment plant needed a NPDES permit to discharge pollutants into underground injection wells.

The wells led the plant’s discharges to groundwater, which carried the pollutants to the Pacific Ocean. Because the Pacific is a WOTUS, citizen groups argued that the treatment plant should have obtained a NPDES permit before discharging pollution.

The Court agreed with those groups, partly, deciding that discharging pollution to groundwater sometimes requires a NPDES permit. Sometimes, the Court reasoned, discharging pollution to groundwater is “functionally equivalent to discharging pollution directly to a WOTUS.

The purpose of EPA’s draft guidance is to help facilities determine when a discharge to groundwater meets this “functional equivalent” standard (and therefore requires a NPDES permit). 

EPA will accept public comments on the new Maui/NPDES draft guidance until December 27, 2023. 

When is a NPDES Permit Required?

The Clean Water Act NPDES permitting program requires any person to obtain a permit before discharging "any pollutant to navigable waters from any point source." To determine when a NPDES permit is required to discharge pollutants to groundwater, the facility first must determine if the discharge will eventually reach a water of the United States. 

If the pollutants will reach a WOTUS, the facility must determine whether that discharge is “functionally equivalent” to a direct discharge to the navigable water. This determination must be based on a variety of factors which EPA gives details about in the draft guidance. 

In addition to outlining general principles for an “overall approach” to NPDES permitting decisions with respect to groundwater pollution, EPA’s draft guidance provides a list of considerations included in the Supreme Court’s Maui decision. 

Factors for determining NPDES applicability (i.e., "functional equivalence") for a discharge to groundwater that reaches a WOTUS include: 

  • Transit time and distance traveled to reach the WOTUS (The draft guidance calls this the “most important factor in most cases, an in many cases the only factor that need be considered…”).
  • The manner or area in which the pollutants enter the water of the US. 
  • The nature of material through which the pollutant travels. 
  • The amount and concentration of pollution. 

From EPA's draft guidance:

“If the operator does not seek permit coverage for a functionally equivalent discharge, the operator may be subject to administrative or judicial enforcement proceedings and associated liability under the CWA (including civil and criminal penalties.”

US EPA, Applying the Supreme Court's Maui Decision... ("Maui Draft Guidance")

Last Complete EPA Regulations Training of the Year

Get in on our final Complete Environmental Regulations Webinar of the year to catch up with rapidly evolving EPA rules and policies under the Clean Air Act, Clean Water Act, TSCA, EPCRA, CERCLA/Superfund, and other major programs.

This unique and deeply-detailed training spans two days (December 14–15) and prepares professionals to identify relevant environmental programs and provisions for their facility and take the right steps to achieve compliance. 

Find a Post

Compliance Archives

Lion - Quotes

Lion courses always set the bar for content, reference, and practical application. Membership and access to the experts is an added bonus.

John Brown, CSP

Director of Safety & Env Affairs

Much better than my previous class with another company. The Lion instructor made sense, kept me awake and made me laugh!

Marti Severs

Enterprise Safety Manager

The instructor was very very informative, helpful, understandable and pleasant. This course answered many questions I had, being new to this industry.

Frances Mona

Shipping Manager

The instructor created a great learning environment.

Avinash Thummadi

CAD & Environmental Manager

The instructor was very engaging and helped less experienced people understand the concepts.

Steve Gall

Safety Leader

Very witty instructor, made the long times sitting bearable. One of the few training courses I can say I actually enjoyed.

John Hutchinson

Senior EHS Engineer

I like the consistency of Lion workshops. The materials are well put together and instructors are top notch!

Kevin Pylka

Permitting, Compliance & Environmental Manager

I will never go anywhere, but to Lion Technology.

Dawn Swofford

EHS Technician

I have over 26 years of environmental compliance experience, and it has been some time since I have attended an environmental regulations workshop. I attended this course as preparation for EHS Audits for my six plants, and it was exactly what I was looking for.

Frank Sizemore

Director of Regulatory Affairs

Excellent class, super instructor, very easy to follow. No rushing through material. Would like to take his class again.

Lawrence Patterson

EH&S Facility Maintenance & Security Manager

Download Our Latest Whitepaper

In-flight hazmat incidents can be disastrous. This guide gives 5 tips for first-time air shippers to consider before offering dangerous goods for transportation on passenger or cargo aircraft.

Latest Whitepaper

By submitting your phone number, you agree to receive recurring marketing and training text messages. Consent to receive text messages is not required for any purchases. Text STOP at any time to cancel. Message and data rates may apply. View our Terms & Conditions and Privacy Policy.