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January 12, 2022  |  Written by Kyler C. Rayden

Proposed New Waters of the United States Rule Reminiscent of Pre-2015 Regulatory Framework

The U.S. Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers (Corps) recently released the long-anticipated proposed rule redefining the scope of waters protected by the Clean Water Act (CWA). The CWA strictly prohibits discharges of pollutants into “navigable waters of the United States” unless specifically permitted; however, the definition of what constitutes “waters of the United States” (WOTUS) has evolved over the past five decades, shifting with the political tides in Washington.

Prior to 2015, WOTUS was defined by regulation (40 C.F.R. § 230.3(s)) and interpreted by U.S. Supreme Court decisions to include the following:

  • Traditional navigable waters (including coastal zones), and adjacent wetlands.
  • “Relatively permanent” non-navigable tributaries of traditional navigable waters, and wetlands that directly abut such tributaries.
  • “Other Waters” which could affect interstate or foreign commerce.
  • Non-navigable tributaries that are not relatively permanent, wetlands adjacent to non-navigable tributaries that are not relatively permanent, and wetlands adjacent to but that do not directly abut a relatively permanent non-navigable tributary that possess a “significant nexus” to traditional navigable waters.

See Solid Waste Agency of Northern Cook County v. U.S. Army Corps of Engineers, 531 U.S. 159 (2001); Rapanos v. United States, 547 U.S. 715 (2006) (Rapanos).

Under the holdings of these landmark cases, courts used the following two tests to determine whether waters fall within the jurisdiction of the CWA:

Significant Nexus Test: A “significant nexus” exists between the tributary or wetland in question and traditionally navigable waters. This fact-specific analysis assesses the flow characteristics and functions of the tributary itself, as well as the functions performed by all wetlands adjacent to the tributary to determine if either “significantly affect” the chemical, physical, and biological integrity of downstream traditional navigable waters.

Relatively Permanent Test: WOTUS includes only those “relatively permanent,” standing or continuously flowing bodies of water forming geographic features ordinarily described as streams, oceans, rivers, and lakes. Notably, the phrase “relatively permanent” generally exempts tributaries that flow “intermittently” or “ephemerally,” or channels that “periodically” provide drainage for rainfall.

In 2015, at the direction of the Obama administration, the EPA and Corps promulgated the Clean Water Rule, significantly expanding the CWA’s jurisdiction by broadening the definition of WOTUS. Five years later, the Trump administration repealed and replaced the Obama-era rule with the Navigable Water Protection Rule (NWPR), significantly narrowing the definition of WOTUS and the scope of CWA’s jurisdiction, including the categorical exclusion of ephemeral streams. In 2021, U.S. District Courts in Arizona and New Mexico repealed and vacated the NWPR, citing “fundamental, substantive flaws that cannot be cured without revising or replacing the NWPR’s definition of ‘waters of the United States.’”[1] The agencies subsequently halted implementation of the NWPR, began interpreting WOTUS consistent with the pre-2015 regulatory regime, and announced their intention to adopt revised regulations.

Last month, the Biden administration circulated new proposed regulations that would restore the longstanding, familiar pre-2015 interpretation of WOTUS, and codify the Supreme Court’s holding in Rapanos. For example, the proposed regulations incorporate the “significant nexus” and “relatively permanent” tests to help determine the CWA’s jurisdiction, and further expand CWA’s jurisdiction over wetlands. While the proposed regulations may help to clarify the definition of WOTUS, stakeholders who backed the narrower NWPR will likely seek injunctive relief as soon as the regulations are published in the Federal Register.

The EPA and Corps are currently seeking comments on numerous contentious topics within the proposed regulations, such as whether the final rule should define the terms “intermittently,” “ephemerally,” or “periodically” as used in  the “relatively permanent” test, as well as the phrase “significantly affect” as used in the “Significant Nexus” test. The agencies are hosting virtual public hearings on January 12th, 13th, and 18th, and the comment period for the proposed regulations closes on February 7, 2022.

For further information please contact Kyler Rayden at

Somach Simmons & Dunn provides the information in its Environmental Law & Policy Alerts and on its website for informational purposes only. This general information is not a substitute for legal advice, and users should consult with legal counsel for specific advice. In addition, using this information or sending electronic mail to Somach Simmons & Dunn or its attorneys does not create an attorney-client relationship with Somach Simmons & Dunn.

[1] Pasqua Yaqui Tribe v. United States EPA, No. CV-20-00266-TUC-RM, 2021 U.S. Dist. LEXIS 163921, at *14 (D. Ariz. Aug. 30, 2021); Nation v. Regan, No. 20-CV-602-MV/GJF, 2021 U.S. Dist. LEXIS 184147, at *9 (D.N.M. Sept. 27, 2021).

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