US EPA and Army Corps revisit WOTUS: Implications for project development and permitting

The United States Environmental Protection Agency (EPA) and the US Army Corps of Engineers recently announced a Supplemental Notice of Proposed Rulemaking (Supplemental Proposal) that seeks additional public input on the definition of “Waters of the United States” (WOTUS) under the Clean Water Act (CWA).

Published in the Federal Register on September 9, 2026, the Supplemental Proposal includes a narrower alternative standard than that in the November 20, 2025 proposed rule for determining whether waters are relatively permanent.

The agencies are considering such alternatives as they work toward a final rule implementing the US Supreme Court's decision in Sackett v. EPA, 598 U.S. 651 (2023), which held that the CWA extends only to relatively permanent bodies of water that are connected to traditional navigable waters and to wetlands with a continuous surface connection to those waters. Comments on the Supplemental Proposal are due October 9, 2026.

If implemented, the Supplemental Proposal could substantially reduce waters subject to federal jurisdiction. However, a narrower federal definition would not eliminate environmental obligations; practical effects would likely depend on project-specific circumstances and other applicable regulatory frameworks.

Background: From Sackett to the Supplemental Proposal

In Sackett v. EPA, the Supreme Court held that the CWA extends only to relatively permanent, standing, or continuously flowing bodies of water and to wetlands with a continuous surface connection that makes them “practically indistinguishable” from those waters. Notably, the Court did not define “relatively permanent” with precision, leaving open the question that the agencies’ rulemaking now seeks to answer.

The agencies’ November 20, 2025 proposed rule took a first step toward implementing Sackett, defining “relatively permanent” as containing standing or flowing water “year-round or at least during the wet season.” For wetlands, the 2025 proposal required a continuous surface connection during the wet season, using concepts of adjacency and abutment. The agencies received more than 220,000 public comments on that proposal, with some stating the wet-season concept was imprecise and difficult to administer.

The Supplemental Proposal replaces that wet-season standard with a stricter perennial standard, under which a water body must contain standing or continuously flowing water year-round under ordinary conditions. The approach interprets the term “relatively permanent” under Sackett as requiring year-round flow. The proposal includes a 30-day threshold for temporary interruptions in flow: A water body that dries up for more than a single period of up to 30 consecutive days in any given year due to non-anomalous events, such as low tide or a regularly occurring dry spell, would lose jurisdictional status. Only extreme and exceptional droughts on the US Drought Monitor scale (classified as D3 and D4, respectively) would qualify as anomalous events capable of preserving perennial status. A drought lasting continuously for more than five years would be treated as the “new normal,” causing the water to lose its jurisdictional status entirely.

The Supplemental Proposal similarly abandons the wet-season framework for wetlands. Wetlands would be jurisdictional only if they have a continuous surface-water connection to a jurisdictional water body such that it is difficult to distinguish where the water ends and the wetland begins.

One alternative would eliminate the terms “adjacent” and “abutting” from the definition and solely rely on Sackett’s indistinguishability test.

Together, these changes have the potential to significantly narrow federal jurisdiction over both tributaries and wetlands, especially in regions where seasonal or intermittent water features are common.

Additional exclusions and clarifications

The proposal would clarify or reaffirm exclusions from federal jurisdiction for groundwater, certain non-navigable ditches excavated in dry land, prior converted cropland, and qualifying waste-treatment systems. Agricultural exemptions under Section 404(f) would remain available for certain irrigation and drainage ditch construction and maintenance activities.

Implications for stakeholders

The Supplemental Proposal highlights three practical points for CWA jurisdiction:

1. Section 404 permits may decrease. The perennial standard could remove certain ephemeral streams, intermittent drainage features, and wetlands from federal jurisdiction, potentially reducing permit applications, review times, and mitigation obligations.

2. State and local requirements remain. State and local programs may regulate water and wetlands outside federal jurisdiction.

3. NEPA assumptions may need reassessment. If a Section 404 permit previously provided the federal nexus for National Environmental Policy Act (NEPA) review, proponents may wish to reassess at an early stage whether NEPA review is still warranted.

How these changes affect a given project may depend on industry, location, and existing permitting frameworks.

Looking ahead

The Supplemental Proposal does not replace or withdraw the November 2025 proposal; both sets of alternatives remain under consideration. The agencies will consider comments on both as they develop the final rule implementing Sackett and have stated they intend to proceed as expeditiously as possible. Litigation over the final rule is expected, regardless of the approach the agencies ultimately adopt.

Project proponents are encouraged to periodically reassess how the evolving jurisdictional scope could affect project design, permitting strategies, mitigation, and environmental-review assumptions.

How DLA Piper can help

Our Environment, Health, and Safety; Real Estate; and Development, Land Use, and Zoning teams are available to help clients navigate changes to the WOTUS rulemaking and its implications for projects and operations. For more information, please contact the authors.