Key Takeaways
- The Proposed Rule would reduce the scope of waters and wetlands subject to federal Clean Water Act (CWA) protections by amending the definition of “waters of the United States” (WOTUS).
- If finalized as proposed, the new standard would eliminate the need for federal permits in some areas, potentially streamlining some project development.
- Although the proposal seeks to simplify the implementation of Sackett, delineating CWA jurisdiction is inherently technical, and applying the new definitions may still be a complex process.
- The States retain separate regulatory authority, and at least some likely will respond by expanding state jurisdiction over waters within their borders.
- The proposal will likely receive a high volume of comments favoring and opposing the change, and subsequent litigation is all but guaranteed, resulting in continued uncertainty.
- While WOTUS litigation and regulatory shifts are unlikely to end with this proposal, the pendulum swing is expected to narrow, given the guardrails the U.S. Supreme Court set in Sackett in 2023.
- The comment period closes on January 5, 2026.
Background
The Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers (“the Corps”) have again proposed redefining the scope of CWA jurisdiction, this time to align with the Trump administration’s stated goals of streamlining permitting and reducing regulatory burdens. The definition of WOTUS dictates whether activities and operations must apply for CWA permits, be it for discharges into WOTUS of “pollutants” (which require a National Discharge Elimination Permit System (NPDES) permit issued by EPA or a state with an EPA-approved permit program under Section 402) or of dredge or fill materials (which require a permit issued by the Corps or a state with an EPA-approved permit program under Section 404). It therefore affects both project development and industrial and other activities with associated discharges.
The scope of WOTUS has been the subject of decades of debate, ping-ponging rulemakings, and constant litigation (including multiple trips to the U.S. Supreme Court). Since 2015 alone, EPA and the Corps have revised the WOTUS definition five times, most recently following the Supreme Court’s landmark decision in Sackett v. EPA, 598 U.S. 651 (2023). But legal challenges have resulted in a patchwork regulatory system in which 26 states need not adhere to the 2023 WOTUS definition, which purportedly aligned with the Sackett concept of WOTUS. In those 26 states, courts have enjoined the Biden administration’s amended definition, so the Agencies are applying their pre-2015 WOTUS framework, which they assert is consistent with Sackett.
In the other half of the country, the 2023 Biden-era rule governs. The rule covers traditionally navigable waters (such as territorial seas and major river systems), relatively permanent tributaries, and wetlands that have a continuous surface connection to relatively permanent or permanent WOTUS, such that the wetlands are virtually indistinguishable from the WOTUS. The rule also carves out eight exclusions for categories of features not subject to CWA jurisdiction.
With the intent of ensuring field staff uniformly identify wetlands consistent with the Sackett framework, in March 2025, EPA issued additional guidance on the meaning of “continuous surface connection” for adjacent wetlands. That same month, the Agency announced a series of listening sessions to help formulate the now-Proposed Rule. In the months that followed, the agencies reported a recurring theme in public feedback: whether discrete features (natural or manmade) sever jurisdiction for wetlands.
Key Proposed Changes
1. Defining “Continuous Surface Connection”
The agencies are soliciting information to clarify the phrase: “continuous surface connection.” Their proposed definition would add two conditions to WOTUS: (1) the water must maintain itself as surface water throughout the “wet season” and (2) the water must abut—i.e., physically touch—existing WOTUS.
The proposal does not define “wet season,” but the agencies float two approaches. One idea would be to define “wet season” based on data obtained from the “Web-based Water-Budget Interactive Modeling Program” (“WebWIMP”). Alternatively, the agencies suggest they could codify “wet season” with a fixed definition, for which there are four proposed metrics: (1) months where precipitation exceeds evapotranspiration, (2) months accounting for lagged snowmelt flow, (3) the three wettest months of the year, and (4) percentage thresholds. At bottom, the agencies emphasize that they want the “wet season” concept to create a “duration threshold” that will operate as a bright-line rule, with room for “regional variation[s]” in hydrology and precipitation.
The “abutment” requirement, the agencies say, should mean “touching” as defined in the March 2025 Continuous Surface Connection guidance document. So, wetlands must touch WOTUS, which would sever jurisdiction when pipes, culverts, or ditches disrupt “continuous surface connection” under this new definitional approach.
To be clear, however, the agencies are not wedded to the “wet season” framework. They also offer three alternatives. The first, a stricter option, would call for year-round surface water. The second would require only that the wetland touch WOTUS, regardless of hydrology. The third approach would set a minimum number of days in which a wetland is inundated to the point that surface water forms.
Finally, the Proposed Rule would also change the approach for classifying mosaic wetlands. Mosaic wetlands would no longer be considered a single, unified feature, but rather, each individual wetland within the mosaic would be classified individually, where only the portion of the wetland that meets the continuous surface connection standard could be jurisdictional.
2. The Elimination of Interstate Waters as a Stand-Alone Category
The agencies propose to remove independent, categorical jurisdiction over interstate waters because such features are not necessarily within the scope of jurisdiction recognized by the Supreme Court in Sackett: i.e., waters are “relatively permanent” and “connected to traditional interstate navigable waters.” Interstate waters have been included in the definition of “navigable waters” since EPA first issued NPDES regulations in 1973. The Army Corps has included interstate waters in its definition of “navigable waters” since 1977. To date, those definitions have not considered factors such as permanence, connection, or navigability.
According to the agencies, however, regulating any waterbody that crosses state lines, regardless of its characteristics, removes a limit on authority that Congress intended in the CWA. The agencies, therefore, propose only including an interstate waterbody if it meets the other criteria that will remain. These include traditional navigable waters or the territorial seas, relatively permanent tributaries of traditional navigable waters or the territorial seas, wetlands with a continuous surface connection to these waters, or impoundments of otherwise jurisdictional waters. This departs from long-standing arguments made by the agencies, which previously maintained that the term WOTUS unambiguously covers waters that cross state lines.
While a significant departure from the current rule, the impacts of this removal may not be as severe as critics claim. In practice, interstate status has rarely been the sole basis for determining that waters are subject to CWA jurisdiction. According to the agencies, only 15 jurisdictional determinations over the last 10 years have been based solely on the waterbody’s interstate nature. In most cases, an interstate waterbody will likely still be jurisdictional under the remaining criteria. Still, this issue is likely to attract significant public comment and litigation from public interest groups.
3. Other Changes
The proposal would limit and clarify the definition of WOTUS in several other respects. It would add a definition of “tributary” to the regulations and define a “tributary” to exclude surface flow that passes through a channelized feature like a culvert, dam, or “similar artificial feature.” It would similarly exclude surface flow that passes through a “debris pile, boulder field, wetland, or similar natural feature.”
The proposal also would revise the exclusions for waste treatment systems, previously converted cropland, and ditches. The Proposed Rule would define “waste treatment system” to clarify what components are considered part of the system to which discharges are excluded. The proposal would also define “ditches” to clarify that ditches that are constructed or excavated entirely on dry land are not WOTUS. The proposal also adds an exclusion for groundwater, which has long been understood to be outside the scope of the statute.
4. Reduced Jurisdiction Likely, But Uncertainty Guaranteed
If the proposal is finalized as written, it will reduce the scope of activities requiring CWA permits, simplifying project development, facility operation, and other activities for those that fall outside federal jurisdiction. The impact may be most significant in arid regions (like in portions of the Western United States), where the more restrictive proposed definitions may have the greatest impact due to decreasing snowpack, earlier snowmelts, and higher rates of evapotranspiration, and coastal plain locations where hydrology is dominated by groundwater.
To be clear, however, the proposed revisions are unlikely to eliminate the complexities associated with defining CWA jurisdiction. These jurisdictional questions are inherently challenging and technical, and applying the definition of WOTUS to a particular site will typically still require site-specific analysis and the assistance of scientific and regulatory experts.
Moreover, a clearer federal WOTUS definition does not affect additional state rules that apply on top of the WOTUS rule. About half of the States have distinct definitions of jurisdictional waters under their own State laws. Those States will continue to issue permits under State authority. States reacted to the Sackett decision by seeking to assert jurisdiction under State law, including Colorado and New York.
Once finalized, no matter the specifics chosen by the agencies, litigation will inevitably follow to challenge the Trump administration’s definition of WOTUS. We know this because it has been the case for past efforts to bring clarity and stability to this area of the law. And although the Sackett decision will limit future definitional changes to some extent by foreclosing certain definitional frameworks, future litigation challenges may occur that stymie attempts to better clarify the definition of WOTUS if administrations seek to revise it yet again.
Next Steps
- Assess jurisdictional determinations that impact your regulatory obligations and consider what changes, if any, might result from the new criteria.
- Interested stakeholders should prepare comments and monitor the progress of this rulemaking process. The comment period closes on January 5, 2026.
Peter Selimos contributed to this article