Audit, Compliance and Risk Blog

EPA and Corps of Engineers redefine “Waters of the United States” in response to Supreme Court

Posted by Jon Elliott on Tue, Sep 19, 2023

Clean waterOn September 8, 2023, the US Environmental Protection Agency (EPA) and US Army Corps of Engineers (Corps) adopted revised definitions of “waters of the United States” (WOTUS) which is a critical but undefined term in the Clean Water Act (CWA). As I’ve discussed repeatedly, the agencies, potentially regulated entities, and others have disputed possible definitions for decades. Most recently, in May 2023 the US Supreme Court adjusted its own precedent to over-rule definitions adopted by EPA and the Corps in January 2023 (I discussed the January rules HERE, and the Supreme Court decision (Sackett v. EPA) HERE). The rest of this note identifies the newest regulatory (re)definitions, adopted to conform the agencies’ regulations to the latest Supreme Court guidance restricting the types of wetlands potentially considered to be WOTUS subject to CWA regulation.

How have the definitions been questioned in recent years?

As I’ve discussed in earlier blogs, since CWA does not define “waters of the United States” the extent of federally regulable waters and wetlands has been unclear since the original Federal Water Pollution Control Act was enacted in 1972. Beginning in 2001 a series of US Supreme Court decisions frayed the expansive edges of interpretations contained in regulatory definitions adopted in 1986. These decisions triggered a series of rulemakings through which EPA and the Corps sought to reconcile Supreme Court decisions with the agencies’ policy preferences (remember that agency preferences varied across the Obama, Trump, and now Biden administrations). The agencies finished a long-running round of rulemakings in January 2023, leading to the Supreme Court’s May 2023 decision.

What does the Supreme Court’s Sackett decision decide?

As I described in the blog linked above, in Sackett a majority of the Supreme Court re-tooled the Court’s own precedent (primarily in the 2006 Rapanos decision) and accordingly rejected important pieces of the agencies’ January 2023 changes to WOTUS definitions. The majority interpretation:

  • Rejects the “significant nexus” test for extending WOTUS beyond waters that are “navigable in fact” as being too ambiguous,, especially since EPA policies that punish noncompliance effectively require detailed geographic and legal analyses before any work is possible at many locations
  • CWA’s use of “waters” encompasses “only those relatively permanent, standing or continuously flowing bodies of water ‘forming geographic[al] features’ that are described in ordinary parlance as ‘streams, oceans, rivers, and lakes’” (affirming the restrictive plurality view in Rapanos)
  • “CWA extends to only those wetlands that are ‘as a practical matter indistinguishable from waters of the United States.’ [quoting the Rapanos plurality]” [put another way, wetlands must be “adjacent” to WOTUS, with a “continuous surface connection”}

How do the new rules incorporate Sackett?

On August 29, EPA and the Corps have now issued revisions to their regulatory definitions of WOTUS,, adjusting their partially-rejected versions from January 2023 to conform to the new Supreme Court guidance. Revisions consist of:

  • Removing the text “including interstate wetlands” from the definitions of “interstate waters”
  • Clarifying that eligible “tributaries” are limited to tributaries of waters that qualify as WOTUS
  • Removing as a potential independent basis for wetlands eligibility “That either alone or in combination with similarly situated waters in the region, significantly affect the chemical, physical, or biological integrity of [tributaries of WOTUS]”
  • Removing text that included the following types of wetlands “Waters identified in paragraph (a)(2) or (3) of this section [i.e., qualifying impoundments and tributaries] when the wetlands either alone or in combination with similarly situated waters in the region, significantly affect the chemical, physical, or biological integrity of waters identified in paragraph (a)(1) of this section [i.e., WOTUS]”
  • Removing as a potential independent basis for Intrastate lakes and ponds eligibility “That either alone or in combination with similarly situated waters in the region, significantly affect the chemical, physical, or biological integrity of [tributaries of WOTUS]”
  • Revising definition of “adjacent” to narrow it to “Adjacent means having a continuous surface connection” [formerly was “Adjacent means bordering, contiguous, or neighboring. Wetlands separated from other waters of the United States by man-made dikes or barriers, natural river berms, beach dunes, and the like are “adjacent wetlands.””]
  • Deleting the definition of “significantly affect”

Readers can find the January 2023 definitions of WOTUS in my blog covering that version of the rules, in which I quote the definition in its entirety.

What now?

The revised rules are effective on September 8, upon publication in the Federal Register. Given the many rounds of litigation that preceded this version, I won’t even try to predict whether there may be subsequent litigation claiming that these latest revisions fail to conform adequately to Sackett.

Self-Assessment Checklist

Does my organization routinely discharge wastewaters:

  • Into a natural water body?
  • Into an artificial conveyance (ditch, storm sewer, etc.)?
  • Into a sanitary sewer system?

Does my organization operate a facility where rainwater or snowmelt might flow:

  • Into a natural water body?
  • Into an artificial conveyance (ditch, storm sewer, etc.)?

Is my organization undertaking a construction or other project that disturbs a waterway, or disturbs soil or rock that might contaminate runoff into a waterway?

Has my organization evaluated the receiving waters to determine whether they qualify as “waters of the United States” subject to CWA requirements?

  • Under the previous definitions?
  • Under the new definitions?

Has my organization evaluated requirements under state laws in each state in which activities may affect water bodies or wetlands?

Where can I go for more information?

About the Author

jon_f_elliottJon Elliott is President of Touchstone Environmental and has been a major contributor to STP’s product range for over 30 years. 

Mr. Elliott has a diverse educational background. In addition to his Juris Doctor (University of California, Boalt Hall School of Law, 1981), he holds a Master of Public Policy (Goldman School of Public Policy [GSPP], UC Berkeley, 1980), and a Bachelor of Science in Mechanical Engineering (Princeton University, 1977).

Mr. Elliott is active in professional and community organizations. In addition, he is a past chairman of the Board of Directors of the GSPP Alumni Association, and past member of the Executive Committee of the State Bar of California's Environmental Law Section (including past chair of its Legislative Committee).

You may contact Mr. Elliott directly at:

Tags: EPA, clean water, CWA, Clear water, water pollutants, environmental law, water, WOTUS