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Regulatory Updates

Biden Administration Proposes New Definition of “Waters of the U.S”

On December 7, 2021, the U.S. Army Corps of Engineers (USACE) and the U.S. Environmental Protection Agency (USEPA) jointly published a new proposed definition of “waters of the U.S.” When finalized, the new definition would replace the one adopted by the Trump Administration in 2020, making this the third time in the last five years the definition has been revised.

The proposed new definition would restore federal jurisdiction over ephemeral streams, adjacent wetlands, and other water bodies, if the USACE determines that they may “significantly affect” other “waters of the U.S”. 


The December 7, 2021 proposed rule would essentially codify the pre-2015 interpretations of “waters of the U.S.” that USACE and USEPA have been operating under since the U.S. District Court of Arizona overturned the Trump Administration’s Navigable Waters Protection Rule (NWPR) in November 2021 (Pascua Yaqui Tribe v. U.S. Environmental Protection Agency). The NWPR was adopted in April 2020, after the Trump Administration in turn repealed the Obama Administration’s 2015 Clean Water Rule.

The troubled history of this contentious term extends back even further. The pre-2015 interpretations underpinning the December 7 proposed rule have been evolving since passage of the federal Clean Water Act in 1972, largely driven by federal court decisions. Two landmark U.S. Supreme Court decisions have shaped the Agencies’ interpretations of the term in recent years: Solid Waste Agency of Northern Cook County (SWANCC) v. U.S. Army Corps of Engineers, (2001), and Rapanos v. United States (2006).

At the heart of the debate is the question of how small headwater streams, and wetlands and other water bodies not immediately connected to larger rivers and streams, should be regulated. Following the SWANCC and Rapanos decisions, USACE and USEPA issued guidance in an attempt to address the Court’s directives, but did not undertake any new rule changes until adoption of the Clean Water Rule in 2015. The 2015 Clean Water Rule was ultimately repealed on the basis that it went too far in regulating these waters, and the NWPR was vacated because it did not go far enough.


The Biden Administration is now proposing a new definition of “waters of the U.S” it claims will provide a “familiar and implementable” framework for determining what water resources are subject to federal regulation. Under the December 7 proposed rule, “waters of the U.S.” would include:

  • Tidal waters and the U.S. territorial seas
  • “Traditional navigable waters” that are, were, or may be used in interstate or foreign commerce (including recreational use)
  • Interstate waters and wetlands
  • Impoundments in “waters of the U.S.”
  • “Tributaries” to the above waters with “relatively permanent” (perennial or intermittent) flow regimes
  • Ephemeral “tributaries” that, considered alone “or in combination with other similarly situated waters” act to “significantly affect” other “waters of the U.S.”
  • Wetlands located “adjacent” to other “waters of the U.S.” or which meet the “significantly affect” test above
  • Other “relatively permanent” water bodies that are connected to other “waters of the U.S”, or which pass the “significantly affect” test

What’s New?

The principal difference between the Biden Administration’s proposed new definition of “waters of the U.S.” and the one contained in the overturned Trump Administration’s NWPR is that the proposed new definition would restore federal jurisdiction over ephemeral streams, adjacent wetlands, and other water bodies if USACE determines they may, alone or collectively, “significantly affect” other “waters of the U.S”. The NWPR categorically excluded ephemeral streams and non-adjacent wetlands and other waters. On the other hand, the proposed new definition does not go so far as the repealed 2015 Clean Water Rule, which included certain non-adjacent wetlands and water bodies located in floodplains or within specified distances of other “waters of the U.S.”

A copy of the full text of the proposed rule is available on the Federal Register’s website. If you would like to discuss how the outcome of this rule may impact Section 404/401 permits and other regulatory programs under the federal Clean Water Act, please contact B&N’s Katherine Fontaine.