Proposed Waters of the United States Rule Would Limit Clean Water Act’s Reach

December 17, 2018

The US Environmental Protection Agency and the Army Corps of Engineers’ joint proposed definition of “waters of the United States” would eliminate the regulation of waters with a “significant nexus” to certain other covered waters.

The US Environmental Protection Agency (EPA) and the Army Corps of Engineers (Army Corps) (together, the agencies) issued a proposed rule to redefine the “waters of the United States” covered by the Clean Water Act on December 11. Unlike both the 2015 Obama-era rule and previous Bush-era guidance, under the proposed rule “waters of the United States” will no longer include bodies of water that have a “significant nexus” to certain other waters covered by the act. Instead, “waters of the United States” will include only those waters that fall within specifically enumerated categories. The proposed rule is likely to generate significant comment and continued interest and controversy when it is finalized. Indeed, some environmental groups have already stated that they will file legal challenges to the new rule if it is finalized as proposed.


Clean Water Act 

The Clean Water Act applies to “navigable waters,” which are defined in the statute as “waters of the United States, including the territorial seas.” That definition has long been controversial, and both agencies and the courts have repeatedly wrestled with its scope. The definition is also important—it affects the application of key federal regulatory programs under the act, including the Section 402 point source discharge permit program, the Section 404 dredge and fill permit program, and the Section 311 oil spill prevention program.

Rapanos v. United States, 547 U.S. 715 (2006)

The proposed rule, as well as the Obama-era and Bush-era efforts by EPA and the Army Corps to define “waters of the United States,” track to competing opinions from Rapanos v. United States, 547 U.S. 715 (2006). There, a fractured US Supreme Court was unable to form a majority in interpreting “waters of the United States.” Justice Antonin Scalia and three other justices articulated a test based on a “continuous surface connection,” while Justice Anthony Kennedy’s concurrence asked whether the at-issue water had a “significant nexus” to another water of the United States. Because Justice Kennedy’s analysis provided the narrowest grounds for reversal, the “significant nexus” test has been understood by many lower courts as the controlling test post-Rapanos for what constitutes a water of the United States.

President Trump’s Executive Order

This week’s announcement is the second step in what has been a two-step process “intended to review and revise the definition of ‘waters of the United States.’” This process was triggered on February 28, 2017, when US President Donald Trump issued an executive order that asked the EPA and Army Corps to (1) repeal the 2015 EPA rule that defined “waters of the United States”; and (2) issue a revised definition for that term. President Trump’s executive order appears to have been motivated largely by the 2015 rule, promulgated by the Obama-era EPA and Army Corps, which contained a definition of “waters of the United States” that many categorized as an expansive assertion of jurisdiction by the agencies.

In February 2018, the agencies kicked off the process of implementing the executive order by issuing a rule that pushed back the applicability date for the 2015 rule to 2020. That applicability date rule was challenged in a number of district courts, and has been enjoined nationwide.

The current interpretation of the reach of the Clean Water Act is thus very much in flux. After the applicability date rule was enjoined, the 2015 rule took effect in 22 states. But because other district courts have issued preliminary injunctions in cases challenging the 2015 rule, the 2015 rule did not take effect in 28 states. In those states, the scope of the Clean Water Act is currently governed by a combination of an earlier rule and guidance from the Bush-era EPA and Army Corps.

Proposed Rule

While both the 2015 rule and Bush-era guidance relied on Justice Kennedy’s “significant nexus” analysis, President Trump directed the agencies in 2017 to “consider interpreting the term ‘navigable waters’ . . . in a manner consistent with” Justice Scalia’s “continuous surface connection” test. In keeping with the president’s order, the proposed rule incorporates Justice Scalia’s “key concept[]” of “limit[ing] jurisdiction to relatively permanent waters and wetlands with a continuous surface connection to those waters.” At the same time, it disavows the “significant nexus” test driving the 2015 rule,[1] proposing to “eliminate the case-by-case application of Justice Kennedy’s significant nexus test” in favor of a regime with “clear categories of jurisdictional waters.”[2]

The proposed rule thus defines “waters of the United States” as including these seven categories of waters:

  1. Traditional navigable waters
  2. Interstate waters
  3. Impoundments
  4. Tributaries
  5. Certain ditches
  6. Lakes and ponds
  7. Adjacent wetlands[3]

All other waters are “not waters of the United States” covered by the Clean Water Act.[4] Illustrative exclusions include groundwater, ephemeral surface features and diffuse storm water runoff, and water-filled depressions.[5]

Several of those categories also are defined more narrowly than in the 2015 rule. For example, the proposed rule defines “adjacent wetlands” as “wetlands that abut or have a direct hydrologic surface connection to other ‘waters of the United States’ in a typical year.”[6] The term “abut” is further defined as “touch[ing] a water of the United States at either a point or side.”[7] The term “direct hydrologic surface connection” in turn is defined as a surface connection that occurs “as a result of inundation from a jurisdictional water to a wetland or via perennial or intermittent flow between a wetland and a jurisdictional water.”[8] That definition is more restrictive than the definition in the 2015 rule, which included “adjacent waters” and defined the term “adjacent” more broadly.


If adopted as written, the proposed rule will narrow the classes or types of water bodies subject to regulation under the Clean Water Act. The primary means through which that narrowing would occur is by elimination of the “significant nexus” test. That test, which was included in different forms in both the 2015 rule and Bush-era guidance, allowed waters outside of explicitly enumerated categories to nonetheless be regulated under the Clean Water Act if they had a “significant nexus” to certain other covered waters. Particularly under the definition of that test in the 2015 rule, the variety of waters that could be considered to have such a “significant nexus” significantly expanded the scope of the act. In contrast, the proposed rule would render any features that do not meet one of the explicit categories of waters of the United States outside the scope of the act.

The narrower explicit categories under the proposed rule would further contract the jurisdiction of the Clean Water Act. In particular, both the definition of “adjacent wetlands” and the definition of “tributaries” are limited under the proposed rule by focusing on the surface connection of those bodies of water to other waters of the United States.

When finalized, the proposed rule is highly likely to be challenged by environmental groups or other interested stakeholders. In particular, such groups are likely to challenge the rule as impermissibly relying on Justice Scalia’s plurality opinion in Rapanos. Because Justice Scalia only persuaded three other justices to join his opinion, litigants may argue that Justice Kennedy’s broader “significant nexus test” is the controlling test from Rapanos as the narrowest grounds for reversal in that case. Under that theory, a proposed rule that “eliminate[s] the case-by-case application of Justice Kennedy’s significant nexus test” would conflict with the Supreme Court’s determination of the scope of the Clean Water Act in Rapanos. Indeed, the agencies seem to have anticipated this argument. In the proposed rule, they argue that Justice Kennedy’s concurrence has received an overbroad reading since its publication, and that both Justice Scalia’s plurality opinion and Justice Kennedy’s concurrence share a common analytical framework that does not require a case-specific analysis of whether waters have a “significant nexus” to another water of the United States.

Litigants could also potentially challenge the EPA’s departure from its prior rules. Cases including FCC v. Fox Television Stations, Inc., 556 U.S. 502 (2009), have recognized that an agency may have an elevated burden to explain its reasoning if its rule relies on factual findings that contradict those underlying its old policy. The agencies may have also anticipated that argument, justifying their rule in terms of a shift in policy goals and legal reasoning, without necessarily disputing any of the scientific findings in the 2015 rule.

If one thing is certain, continued controversy over the scope of the Clean Water Act is likely. The agencies will likely receive a significant number of comments following the publication of the proposed rule. And if and when the final rule is challenged, the issue could end up back before the Supreme Court.


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[1] Proposed Rule at 157.

[2] Id. at 61.

[3] Id. at 61–132.

[4] Id. at 132–154.

[5] Id.

[6] Id. at 187.

[7] Id.

[8] Id.