Waters of the United States

The EPA and Army Corps of Engineers released a preview of the long-awaited proposed rule updating the definition of “Waters of the United States” yesterday morning. The proposed rule will soon be published in the Federal Register, but the unofficial version of the rule is available now. My initial reaction is that this rule—while being couched in terms of providing “regulatory certainty”—may actually expand the scope of waters regulated under the Clean Water Act (CWA).

Not surprisingly, the EPA and Corps followed Justice Kennedy’s concurring opinion in Rapanos v. United States, that concluded that wetlands were “Waters of the United States” if those wetlands had a “significant nexus” to waters that are or were navigable, or could reasonably be made so. A “significant nexus” was defined by Justice Kennedy as wetlands that “either alone or in combination with similarly situated [wet]lands in the region, significantly affect the chemical, physical or biological integrity of other covered waters more readily understood as navigable.” This definition of significant nexus runs throughout the just-released proposed definition of “Waters of the United States,” and uses Kennedy’s language and concepts.

The core of the proposed definition of the “Waters of the United States” are waters that have been traditionally regulated under the CWA and the Rivers and Harbors Act pursuant to Congress’s Commerce Clause authority, i.e., navigable waters, including waters that have been navigable in the past or may be susceptible to use in interstate or foreign commerce; wetlands that are interstate in nature; territorial seas; and impoundments of these types of waters. I’ll refer to these waters as “traditional waters” through the rest of this post.


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