On May 27, 2015, the United States Environmental Protection Agency and the United States Army Corps of Engineers released a final rule expanding federal jurisdiction under the Clean Water Act. The rule expands on existing law by asserting jurisdiction over all tributaries to traditional navigable waters—without regard to the quantity or timing of flow—and by creating a new class of “adjacent waters” that is much broader than the “adjacent wetlands” that are currently regulated.

The final rule redefines the term “waters of the United States,” which establishes the jurisdictional reach of all Clean Water Act programs, including but not limited to wetlands (Section 404), stormwater and other discharges (Section 402), and oil spill prevention and response (Section 311).

The initial proposed rule was extremely controversial, generating over 1 million comments and strenuous opposition from many sectors. In response to these comments, the agencies included an important new exemption for stormwater infrastructure, clarified that most ditches and “erosional features” with less than perennial flow are not covered, and expanded an exemption for artificial lakes and ponds.

Notwithstanding these and other improvements and clarifications, the final rule unquestionably expands federal jurisdiction while leaving many important questions to be resolved through litigation. For example, because ephemeral tributaries will now be covered but ephemeral “ditches” and “erosional features” will not be, the distinction between these types of drainage features is critical, but the terms “ditch” and “erosional feature” are not defined in the rule.

The new class of “adjacent waters” may also be tested through litigation, especially to the extent the new rule appears to recapture “isolated” waters and wetlands previously exempt. The term “adjacent” is defined very broadly as potentially including all wetlands and waterbodies within the 100-year floodplain. All such waterbodies are included by rule if they are within 1,500 feet of the ordinary high water mark of a covered waterbody, and on a case-by-case basis if they are further away.

In sum, the final rule has major implications for any business that develops or alters land—including state and local governments, utilities, energy companies, mining operations, developers, road builders, pipeline operators, reservoir builders, and many others. Some projects that previously would not have required a Clean Water Act permit will now be subject to regulation; and some that could have benefited from expedited permitting procedures will no longer qualify.

Furthermore, given the fact that this rule concerns the jurisdictional reach of all Clean Water Act programs, it has significant implications for stormwater and MS4 permitting. While the rule does provide an exception for certain stormwater features, municipalities with MS4 permits must now determine which stormwater conveyance structures are jurisdictional and how to incorporate these features into their permit programs such as monitoring and inspections.

The new rule will take effect 60 days after it is published in the Federal Register. Jurisdictional determinations associated with existing permits and with completed permit applications and pre-construction notifications will generally not be affected.