EPA and the Army Corps of Engineers (the agencies) recently proposed regulations that would amend the definition of "waters of the United States" under the Clean Water Act (CWA). The revised definition would apply to all CWA programs and is likely to substantially expand the agencies' jurisdiction. The proposed rule change would not only alter permitting programs under the CWA, such as the National Pollutant Discharge Elimination System or Section 404, but it may also expand other regulatory obligations, such as the requirement to develop spill prevention, control and countermeasure plans, on the basis that a release of oil could reasonably discharge into jurisdictional waters.

Expanded Definition of "Waters of the United States"

Under the proposed revision, the term "waters of the United States" would continue to include classes of waters historically regulated under the CWA but the regulated waters within several of these classes would expand. More specifically, the proposed rule would greatly expand the CWA's reach over tributaries and certain defined wetlands and adjacent waters in addition to retaining agency jurisdiction over interstate waters and wetlands, the territorial seas, and other waters that could affect interstate or foreign commerce.

Expanded Definition of "Tributaries"

Under the current regulations, "tributaries" are included within the definition of "waters of the United States." A prior 2008 joint-agency guidance (2008 Guidance) interpreting the United States Supreme Court's decision in Rapanos v. United States and Carabell v. United States (jointly Rapanos), expanded the reach of the CWA to include non-navigable tributaries that are relatively permanent (defined as seasonal flow during at least three months out of the year) and tributaries that have a "significant nexus" to navigable waters.

The proposed new rule would further expand jurisdiction by regulating "all tributaries," indicating that the agencies will assert jurisdiction over every headwater in the United States, regardless of its nexus to the traditional navigable water. In addition, the agencies are proposing to define the term "tributary" for the first time. Under the proposed regulations, a "tributary" would be defined physically by "the presence of a bed and banks and ordinary high water mark." This definition does not require that surface water continuously exist in the water feature, and therefore would likely include many ephemeral tributary streams. By definition, wetlands, lakes and ponds that contribute flow to jurisdictional waters would also be considered tributaries under the proposed regulations despite lacking banks and a high water mark.

Expanded Definitions of "Adjacent" and "Neighboring"

In addition, the proposed regulations add new dimensions to the meaning of the term "adjacent." Existing regulations cover only adjacent wetlands, whereas the proposed regulations cover both adjacent waters and wetlands. Further, while the term "adjacent" would continue to be defined to mean "bordering, contiguous, or neighboring," the proposed regulations add a new definition for the term "neighboring." "Neighboring" waters would include "waters located within the riparian area or flood plain of" waters of the United States, or "waters with a shallow subsurface hydrologic connection or confined surface hydrologic connection" to waters of the United States. In contrast, the 2008 Guidance allowed for jurisdiction over adjacent wetlands that have a hydrological or "ecological interconnection" with jurisdictional waters. The new definition does not require any nexus analysis and will thus substantially expand the reach of the CWA to include entire floodplains or riparian areas that may not have been previously regulated under the Act.

The "Substantial Nexus" Concept

The regulations also seek to incorporate the "substantial nexus" concept that was previously set forth in Justice Kennedy's opinion in Rapanos, as well as in the 2008 Guidance. Under the proposed new rule, other waters and wetlands that are not per se jurisdictional will be considered "waters of the United States" if those waters have a "significant nexus" to a traditional navigable water, interstate water or the territorial seas. When making this case-by-case determination, the proposed rule allows the agencies to consider whether those waters "alone, or in combination with other similarly situated waters in the region" have a significant nexus. Therefore, one concept that differs from the 2008 Guidance is that the agencies will consider similarly situated waters as "a single landscape unit." Accordingly, under the proposed regulations EPA or the Corps may make classifications of entire watersheds or regions that trigger regulation under the CWA.

The final rule will be supported by a peer-reviewed study regarding the connectivity of tributaries, wetlands and other waters to downstream waters. This study is currently under review by EPA's Science Advisory Board, and the rule will not be finalized until the study is complete. The agencies anticipate publishing the proposed regulations in the Federal Register within the next week and subjecting the proposed rule to a 90-day comment period.

In a separate Federal Register posting, the agencies will also release a new interpretative rule that attempts to clarify when the dredge and fill permitting exceptions of Section 404(f) apply. This new interpretive rule will be effective immediately, though the agencies will accept comments on the rule.