On September 4, 2026, the United States Environmental Protection Agency (U.S. EPA) and the U.S. Army Corps of Engineers (USACE) announced a Supplemental Notice of Proposed Rulemaking (SNPRM) on the definition of waters of the United States (WOTUS). WOTUS is critically important because it defines which streams, wetlands, and other water features fall under federal Clean Water Act (CWA) jurisdiction and, thus, whether a facility or operation will require a CWA permit.
The purpose of the September 2026 SNPRM is for the agencies to supplement and seek additional comment on certain aspects of the previous WOTUS proposed rulemaking from November 2025. A summary of that proposed rulemaking can be found here.
How We Got Here
The September 2026 proposal is the latest chapter in a saga that has run through multiple administrations. The current push traces back to the U.S. Supreme Court’s 2023 decision in Sackett v. EPA, which rejected the broader “significant nexus” test for wetlands jurisdiction and required a “continuous surface connection” to be a qualifying water.
Following Sackett, the agencies published a proposed rule on November 20, 2025, aimed at narrowing and clarifying WOTUS jurisdiction. The proposal drew approximately 220,000 submissions from a wide number and variety of State and Tribal governments, industry groups, agricultural producers, non-profit advocacy groups, interagency partners, and other stakeholders during a 45-day comment period that closed on January 5, 2026. Many of the comments requested more clarity for specific technical definitions, which is what prompted the agencies to go back and supplement the proposal rather than move straight to a final rule.
What’s New in the Supplemental Proposal
The September SNPRM considers revising two definitions added in the November 2025 proposal and also adding a new definition for “perennial,” as summarized below:
- “Relatively permanent” waters. The agencies are proposing to define this term based on the 2020 Navigable Waters Protection Rule which focuses on continuous, year-round surface flow consistent with the common hydrologic understanding of the term “perennial.” The proposal would treat short interruptions (up to 30 consecutive days), such as those caused by drought, low tide, or similar non-anomalous events, as not breaking “relative permanence.”
- “Continuous surface connection” for wetlands. The proposal revisits how to define wetlands connected closely enough to a jurisdictional water to count as “adjacent,” potentially eliminating the standalone definition of “adjacent” altogether in favor of describing the connection directly. As with the permanence standard described above, temporary interruptions from anomalous events like drought wouldn’t necessarily sever the connection.
- The SNPRM proposes to define “perennial” as “having standing or continuously flowing water every day of the year during ordinary conditions” and is meant to align with the common meaning of “perennial” used in hydrology (e.g., as defined in the U.S. Geological Survey’s Water Basics Glossary).
Why It Matters
For industries, farmers, developers, and landowners, WOTUS defines whether a ditch, low-lying field, or wetland near a stream requires a CWA permit before the area can be disturbed. Even projects with no obvious connection to water could potentially be pulled into a jurisdictional review depending on how “relatively permanent” and “continuous surface connection” are ultimately defined.
It’s worth noting that state and local rules can still separately regulate wetlands or ephemeral features that fall outside the federal definition, so changes to develop a clear, enforceable federal definition of WOTUS won’t necessarily mean fewer permitting hurdles in a particular state or locality. According to a recent review of ‘waters of the state’ definitions, as many as 24 states rely solely on the federal definition, while the remaining states regulate with a broader definition. Therefore, site selection becomes even more important in determining regulatory requirements under the CWA.
What Happens Next
Publication of the SNPRM in the Federal Register on September 9, 2026 opened a 30-day public comment window that closes on October 9, 2026. This process, along with likely litigation and state-level responses, will continue shaping this area of environmental law well into 2027 and beyond.
If you need support with CWA compliance or strategy, please reach out to William Shane at wshane@all4inc.com or 859-233-0123.
