On September 9, 2026, EPA and the Army Corps of Engineers published a supplemental notice of proposed rulemaking that builds on the agencies’ November 2025 proposal and seeks comment on additional options for revising the definition of “Waters of the United States” (WOTUS). This definition determines which waters are subject to federal regulation under the Clean Water Act. Environmental groups, industry groups, landowners, and states have repeatedly challenged the definition of WOTUS, resulting in a long and complex regulatory and legal history. Comments on the supplemental proposal are due October 9, 2026.
The Supreme Court’s 2023 decision in Sackett v. EPA limited WOTUS to relatively permanent, standing, or continuously flowing waters. Under Sackett, a wetland is protected only if it is adjacent to a relatively permanent body of water and has a continuous surface connection to that water. The Court explained that a wetland has a continuous surface connection only if it is “as a practical matter indistinguishable from” the adjacent water. The decision let agencies determine how to define those terms, and the agencies now seek comment on possible interpretations.
Following Sackett, the Biden administration issued a conforming rule in 2023. In November 2025, the Trump administration issued a proposed rule containing a narrower interpretation of WOTUS. This September 2026 proposal would adopt an even more restrictive definition of WOTUS than the pending November 2025 proposal, further limiting protections granted under the Biden administration’s amended 2023 rule.
This quick take summarizes the key aspects of the supplemental proposal, describes how it differs from the November 2025 proposal, and outlines the agencies’ likely next steps.