The proposed definition would significantly extend the regulatory scope of the Clean Water Act.

By Michael G. Romey, Cody M. Kermanian, and Lucas I. Quass

On December 7, 2021, the US Environmental Protection Agency and the US Army Corps of Engineers (collectively, the Agencies) published a proposed rule (the Proposed Rule) to revise the definition of “waters of the United States” (WOTUS), a critical term that determines the Clean Water Act’s (CWA’s) scope and application. The proposed changes, published in the Federal Register, could signal a return to the more inclusive pre-2017 WOTUS interpretation, which could broaden the CWA’s application. Comments on the Proposed Rule are due on February 7, 2022.


The Proposed Rule follows a contentious history of regulatory and legal action, which reached a turning point this year.

Since the 1970s, the Agencies have defined WOTUS by regulation. Three US Supreme Court decisions have addressed the definition, the most recent of which was Rapanos v. United States, 547 U.S. 715 (2006). In Rapanos, a four-Justice plurality opinion authored by Justice Antonin Scalia established a narrow definition that included relatively permanent, standing, or continuously flowing bodies of water and wetlands with a continuous surface connection to traditional interstate navigable waters. The plurality’s approach came to be known as the “continuous surface water connection” test. In a lone concurring opinion, Justice Anthony Kennedy provided a much broader interpretation that included waters and wetland that “possess a ‘significant nexus’ to waters that are or were navigable in fact or that could reasonably be so made.” Justice Kennedy’s approach is commonly referred to as the “significant nexus” test.

Because no majority opinion emerged, Rapanos resulted in varied application across the country. In an attempt to resolve the ambiguity that Rapanos created, the Obama Administration prompted the Agencies in 2015 to adopt the “Clean Water Rule,” which broadly redefined WOTUS while relying on the significant nexus test.

On February 28, 2017, then-President Trump issued Executive Order 13778, directing the Agencies to consider repealing the Clean Water Rule and replacing it with a regulation adopting the reasoning of Justice Scalia’s plurality opinion in Rapanos.[i] In 2019, the Agencies then repealed the Clean Water Rule and reinstated the pre-2015 regulations.[ii] The following year, the Agencies promulgated the 2020 Navigable Water Protection Rule (NWPR), which redefined WOTUS while relying in part on the continuous surface water connection test. Over the ensuing months, the NWPR was subject to multiple lawsuits and ultimately vacated in a federal district court decision.[iii] Consistent with this decision, on January 20, 2021, President Biden issued Executive Order 13990, repealing Executive Order 13778.

In light of these changes, the Agencies were once again directed to revisit and revise the definition of WOTUS.

Overview of the Proposed Rule

Under the Proposed Rule, the Agencies interpret the term WOTUS to include:

  • Traditional navigable waters, interstate waters, the territorial seas, and their adjacent wetlands
  • Most impoundments or manmade diversion of WOTUS
  • Tributaries to traditional navigable waters, interstate waters, the territorial seas, and impoundments that meet either the relatively permanent standard or the significant nexus standard
  • Wetlands adjacent to impoundments and tributaries that meet either the relatively permanent standard or the significant nexus standard
  • “Other waters” that meet either the relatively permanent standard or the significant nexus standard[iv]

Inclusion of “other waters” in the definition of WOTUS may be the language that most significantly extends the jurisdiction of the CWA. For instance, the “relatively permanent standard” means waters that are relatively permanent, standing, or continuously flowing and waters with a continuous surface connection to waters.[v] Meanwhile, the “significant nexus standard” means “waters that either alone or in combination with similarly situated waters in the region, significantly affect the chemical, physical, or biological integrity of traditional navigable waters, interstate waters, or the territorial seas.”[vi]

Although case-specific determinations would still need to be made under the Proposed Rule, the Agencies believe that its adoption, which signifies a return to the pre-2017 definition, would provide a known and familiar framework for regulators and stakeholders.

Next Steps

The public comment period for the Proposed Rule is open until February 7, 2022. During the comment period the Agencies will consider all public comments on the Proposed Rule including changes that improve clarity, implementability, and long-term durability of the definition. The Agencies are also seeking stakeholder comments on specific aspects of the Proposed Rule, such as whether to consolidate the traditional navigable waters, interstate waters, and the territorial seas provisions into one provision; how to identify a tribal boundary for purposes of interstate waters; how expansive the term “other waters” should be; all aspects of the tributary provision; and exclusions to the regulation. Latham will continue to monitor developments related to the Proposed Rule.

[i] 82 Fed. Reg. 12, 497 (Feb. 28, 2017).

[ii] 84 Fed. Reg. 56, 626 (Oct. 22, 2019).

[iii] (Pasqua Yaqui Tribe v. United States Envtl. Prot. Agency, CV-20-00266-TUC-RM (D. Ariz. Aug. 30, 2021) [vacating the NWPR]. See Colorado v. U.S. Environmental Protection Agency, 445 F. Supp. 3d 1295 (D. Colo. 2020), rev’d, 989 F.3d 874 (10th Cir. 2021); Conservation Law Foundation v. USEPA, CV-20-10820-DPW (D. Mass. Sept. 1, 2021).

[iv] 86. Fed. Reg. 69372, 69372 (Dec. 7, 2021).

[v] Ibid.

[vi] Ibid.