EPA Proposes New Rule to Redefine “Waters of the United States”

In a significant regulatory move, the U.S. Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers have unveiled a proposed rule on November 20, 2025, seeking to revise the definition of “waters of the United States” (WOTUS) under the Clean Water Act (CWA). This proposal is set to reshape the federal oversight landscape for industries reliant on water resources.

The WOTUS definition plays a crucial role in determining the federal jurisdiction scope over various CWA programs, particularly those involving discharge and construction permits.

Significance of the Proposed Rule

Adjusting the WOTUS definition has far-reaching implications for industries such as construction, energy, and agriculture, impacting project costs, compliance obligations, and permitting timelines. Should the rule be finalized, the federal jurisdiction is expected to contract, reducing the number of waterbodies under CWA regulation. Stakeholders have until January 5, 2026 to submit their comments, a period that is notably short due to the holiday season.

Understanding WOTUS and Its Regulatory Impact

The Clean Water Act governs “navigable waters,” presently defined as WOTUS. Key programs reliant on this definition include:

• Section 402 (NPDES) – permits for pollutant discharges
• Section 404 – permits for dredged or fill material

Lacking a statutory definition, WOTUS has historically been shaped by a series of rulemakings, court rulings, and regional variations, leading to significant confusion. Currently, WOTUS encompasses five categories of waters, like navigable waters and tributaries, while excluding eight types, such as waste treatment systems and certain ditches. The new proposal aligns with the Supreme Court’s 2023 ruling in Sackett v. EPA, which curtailed federal jurisdiction over wetlands.

Proposed Modifications to WOTUS

If enacted, the proposed changes would:

1. Exclude “interstate waters” from the WOTUS definition;
2. Introduce definitions for terms including:

   1. “Relatively Permanent;”
   2. “Tributary;” and
   3. “Continuous Surface Connection.”

3. Revise exclusions for water treatment systems, prior converted cropland, and certain ditches, additionally excluding groundwater from WOTUS.

These proposals aim to curtail federal oversight, particularly in regions with arid climates or seasonal water flows. It is estimated that only 19% of wetlands in the National Wetlands Inventory would qualify for jurisdiction under this rule.

Clarification of New Terms

The introduction of new terms seeks to bring clarity to WOTUS in line with the Sackett decision.

“Relatively Permanent”

The term “relatively permanent” is defined as “standing or continuously flowing bodies of surface water that are standing or continuously flowing year-round or at least during the wet season.” This definition is pivotal as it determines whether tributaries, lakes, ponds, and wetlands fall under CWA jurisdiction. The proposed definition excludes ephemeral waters which respond directly to precipitation. Features in arid areas might be excluded due to their sporadic water flow.

“Tributary”

Incorporating “relatively permanent” into the “tributary” definition, it describes “a body of water with relatively permanent flow, and a bed and banks, that connects to a downstream traditional navigable water or the territorial seas.” This definition is crucial as it significantly influences the jurisdictional reach of the CWA. Features without relatively permanent flow could disrupt upstream jurisdiction, a change expected to affect regions like the arid West.

“Continuous Surface Connection”

A “continuous surface connection” means “having surface water at least during the wet season and abutting (i.e., touching) a jurisdictional water.” This two-pronged test determines WOTUS qualification for wetlands, ponds, and lakes. Only portions of wetlands with surface water during the wet season would be jurisdictional, potentially reducing CWA coverage to 19% of National Wetland Inventory wetlands.

Anticipated Outcomes and Future Steps

The Proposed Rule is poised to reduce the number of waterbodies classified as WOTUS, simplifying the regulatory landscape for CWA enforcement. The public comment period concludes on January 5, 2026, with the final rule anticipated within six months. The final rule is expected to mirror the proposed one closely due to its foundation on the Sackett decision. Regulatory entities and stakeholders should prepare for compliance adjustments once the rule is enacted.