WOTUS Proposed Rule Comment Period Ends January 5, 2026

The Environmental Protection Agency ("EPA") and the U.S. Army Corps of Engineers ("Corps") recently published a proposed rule updating the definition of "waters of the United States" ("WOTUS"). This alert briefly describes the proposed changes, why it matters, and next steps.

Background

The Clean Water Act ("CWA") has jurisdiction over WOTUS. How WOTUS is defined dictates the breadth of federal water regulation. Throughout the years, the definition of WOTUS has changed with presidential administrations. In a previous alert, we discussed rule changes issued in 2015, by the Obama administration. In 2018, the first Trump administration issued a rule changing the applicability date of the 2015 rule. The goal was to provide time to write a new rule before the new applicability date. Then in 2019, the Trump administration issued a rule repealing the 2015 rule and reinstating the old 1986 rule. The Biden administration broadened the definition of WOTUS in its 2023 rule. Shortly after, the U.S. Supreme Court declared the 2023 definition of WOTUS is too broad in Sackett v. EPA. The Biden administration then issued a "conforming rule" to align with Sackett v. EPA. In March 2025, the EPA and the Corps signed a joint memorandum providing further guidance on WOTUS after Sackett v. EPA.

Proposed Rule

Now the second Trump administration is proposing a rule changing the definition of WOTUS again. The proposed changes are intended to make the definition of WOTUS more in line with prior U.S. Supreme Court's rulings. Major proposed changes include:

Adding definitions for "relatively permanent" and "continuous surface connection"

• "Relatively permanent" is proposed to be defined as "standing or continuously flowing bodies of surface water that are standing or continuously flowing year-round or at least during wet season." Adding this definition is intended to exclude surface waters resulting from precipitation—consistent with Sackett v. EPA.
• "Continuous surface connection" is proposed to be defined as "having surface water at least during the wet season and abutting (i.e., touching) a jurisdictional water." Requiring wetlands to be both touching jurisdictional water and having a surface connection during the wet season will likely result in fewer wetlands being covered under CWA.

Re-establishing definitions for "tributary"

• "Tributary" is proposed to be defined as "a body of water with relatively permanent flow, and a bed and bank, that connects to a downstream traditional navigable water or the territorial seas, either directly or through one or more waters or features that convey relatively permanent flow." Requiring relatively permanent flow and a connection to downstream traditional navigable water is consistent with U.S. Supreme Court precedent.

Deleting the interstate waters category

The interstate waters category can include bodies of water that are not relatively permanent, standing, continuously flowing, or connected to a navigable water. Removing this category would not have many practical impacts because waters are rarely regulated under CWA solely for the interstate waters category.

Revising the exclusions for waste treatment systems, prior converted cropland, and ditches

• The waste treatment system exclusion is proposed to clarify the definition of "waste treatment system." The definition of "waste treatment system" would include "all components of a waste treatment system designed to meet the requirements of the Clean Water Act, including lagoons and treatment ponds (such as settling or cooling ponds), designed to either convey or retain, concentrate, settle, reduce, or remove pollutants, either actively or passively, from wastewater prior to discharge (or eliminating any such discharge)." This modification is intended to clarify that lagoons and treatment ponds are portions of a waste treatment system.
• The prior converted cropland exclusion is proposed to be modified to clarify that abandoned cropland that has reverted to wetlands no longer qualifies for this exclusion. A full wetland determination, however, is still needed.
• The ditch exclusion is proposed to be modified by defining a "ditch" as "a constructed or excavated channel used to convey water." This definition is intended to simplify and clarity the ditch exclusion.

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