In Rapanos v. United States, 547 U.S. 715 (June 19, 2006), the Supreme Court issued a decision that delineated the extent to which federal regulation extended over water resources. In that case, the petitioner had filled in wetlands on his property without obtaining a permit, and had thereafter been prosecuted for doing so. The decision turned on the meaning of the phrase “waters of the United States” as used in the Clean Waters Act.  

Three opinions emerged. Writing for four Justices, Justice Scalia held that the term “waters of the United States” encompassed waters that were navigable in the traditional sense and abutting wetlands; relatively permanent, standing or continuously flowing bodies of water connected to traditional navigable waters; and wetlands with a continuous surface connection to such waters (the “Scalia test”). In an opinion concurring in the judgment, Justice Kennedy stated that he would hold that wetlands were waters of the United States if the wetlands alone, or in combination with similarly situated lands in the region, significantly affected the chemical, physical and biological integrity of other covered waters more readily understood as navigable (the “Kennedy nexus” test). Four dissenters would have upheld a broad regulatory definition of the term “waters of the United States.”  

A year after Rapanos, the Army Corps of Engineers (“ACOE”) and the Environmental Protection Agency issued a guidance document (“Guidance”). Because a majority of the Court would uphold federal jurisdiction over bodies of water if either the Scalia test or the Kennedy nexus test was met, the Guidance incorporated both. The Guidance divided waters into three classes: those over which it would assert jurisdiction, those for which jurisdiction would be determined by a fact-specific inquiry, and waters for which jurisdiction would generally not be asserted. The first class consisted of the following: 

  • Traditional navigable waters
  • Wetlands adjacent to traditional navigable waters
  • Non-navigable tributaries of traditional navigable waters that are relatively permanent
  • Wetlands that directly abut such tributaries.  

For the following waters in the second class, a fact-specific analysis would be performed:  

  • Non-navigable tributaries that are not relatively permanent
  • Wetlands adjacent to such tributaries
  • Wetlands adjacent to but not directly abutting relatively permanent tributaries  

The third class of waters, which are generally considered outside the jurisdictional reach of the Clean Water Act, include:  

  • Swales or erosional features
  • Ditches excavated wholly in and draining only uplands, and that do not contain a relatively permanent flow of water  

Following publication of the Guidance, the agencies received more than 66,000 public comments (the vast majority—65,765—being duplicative form letters). In light of the comments and the experience gained in processing more than 18,000 jurisdictional determinations, the agencies revised the Guidance on December 2, 2008. The significant revisions were (i) greater definition of the term “traditional navigable waters”; (ii) a change to where flow characteristics are measured for the purpose of assessing whether a tributary is permanent; and (iii) further clarification of the term “adjacent wetlands.”  

Traditional Navigable Waters

Traditional Navigable Waters are now considered to encompass: (i) waters subject to Sections 9 or 10 of the Rivers and Harbors Act; (ii) waters that have been determined to be navigable by a federal court; (iii) waters that are currently being used for commercial navigation, including such commercial recreational activities as boat rental, guided fishing trips and water skiing tournaments; (iv) waters that have historically been used for commercial navigation; and (v) waters that are susceptible to being used in the future for commercial navigation.  

Measurement of Flow Characteristics

In the original Guidance, the flow of a tributary was to be determined at its downstream limit, i.e., where it combined with a higher order stream. The revised Guidance allows flow to be measured at a different point if it is not representative of the tributary. In that case, the flow regime that best characterizes the tributary is to be used.  

Adjacent Wetlands

Under the Guidance, the agencies intend to continue to assert jurisdiction over wetlands that are “adjacent” to traditional navigable waters, and wetlands that “directly abut” relatively permanent tributaries, and will conduct a fact-specific jurisdictional inquiry for wetlands adjacent to such tributaries.  

The fine line between an “adjacent” and a “directly abutting” wetland is addressed in the revised Guidance: “Adjacent” is defined by regulation to mean bordering, contiguous or neighboring. The agencies will therefore consider a wetland to be “adjacent” to a jurisdictional water if (i) there is an unbroken surface connection or shallow subsurface connection between the two; (ii) they are physically separated from jurisdictional waters by man-made dikes or barriers, natural river berms, beach dunes and the like; or (iii) their proximity is reasonably close, supporting the science-based inference that such wetlands have an ecological interconnection with jurisdictional waters. The phrase “directly abutting” is not further defined; presumably it means exactly what it says.  


The revised Guidance provides more clarity than its predecessor, but the agencies themselves note that it will not be the final word. The Guidance states that further changes can be expected as Rapanos is interpreted in the field and by the courts. In addition, the revised Guidance is restricted in application to Section 404 of the Clean Water Act, which is administered by both agencies. The EPA is considering whether to issue a separate guidance to interpret Sections 311 and 402, even though the same jurisdictional term appears throughout the Act.  

It should be noted that shortly before issuing the revised Guidance, the ACOE issued a separate Regulatory Guidance Letter clarifying that project proponents who do not wish their projects to be held up by a protracted jurisdictional determination can request a preliminary determination based on a presumption of jurisdiction. The preliminary determination, which does not constitute a legally binding determination, allows the ACOE to proceed directly to the permitting stage.