With just days left to comment, the U.S. Environmental Protection Agency (EPA) is proposing another revision to the federal definition of Waters of the United States, often referred to as “WOTUS”. Public comments on the proposal are due by January 5, 2026.
Scout has written about this topic before. This is a short look at what we are watching and why changes to this definition could matter for project planning, National Environmental Policy Act (NEPA), permitting strategy, and coordination across federal and state processes.
Why This Definition Matters in the First Place
At first glance, a federal definition of “Waters of the United States” can sound abstract. In practice, it can decide how many approvals a project needs, how long it takes to move forward, and where the risk shows up.
A simple example:
Imagine a project site with a shallow drainage feature that only carries water after heavy rain.
Under prior interpretations, that feature might have been treated cautiously as federally regulated, triggering additional studies, coordination with federal agencies, and potential permitting.
Under the revised definition, that same feature may fall outside federal jurisdiction if it does not have a clear, continuous surface water connection to a larger, permanent body of water.
The difference is not just technical. It can affect:
- Whether a federal permit is required
- How early field work needs to happen
- Which agency reviews become the schedule driver
Why the Definition Is Changing
The proposed rule is largely a response to a 2023 U.S. Supreme Court decision called Sackett v. Environmental Protection Agency.
You can read the decision here:
https://www.supremecourt.gov/opinions/22pdf/21-454_4g15.pdf
Before Sackett, the federal government often evaluated whether a water feature was regulated by looking at whether it had a meaningful ecological connection to downstream waters. This could include wetlands or streams that were nearby or connected underground.
In Sackett, the Supreme Court said that approach went too far.
The Court held that for a wetland to be federally regulated, it must have:
- A clear surface water connection
- To a relatively permanent body of water
- Such that it is difficult to tell where the water ends and the wetland begin
In simple terms, the Court told federal agencies they cannot regulate waters just because they are nearby or connected indirectly. There needs to be a visible, surface-level connection.
EPA is now revising the Waters of the United States definition to reflect that ruling.
The proposed rule also reflects consultation with Tribal Nations. EPA notes that Tribes raised concerns about how changes to the federal definition could affect waters that are important for drinking, fishing, and cultural uses. While the agency is constrained by the Supreme Court’s Sackett decision, the rulemaking process acknowledges these perspectives and signals continued attention to how definitional changes may affect Tribal interests in practice.
What Is Changing
The proposed rule tightens the definition of Waters of the United States by focusing on:
- Relatively permanent waters, such as rivers, streams, lakes, and oceans
- Wetlands that have a continuous surface connection to those waters
This is EPA’s attempt to draw clearer lines around what is federally regulated and what is not.
Key resources:
- EPA overview page: https://www.epa.gov/wotus
- Proposed rule in the Federal Register: https://www.epa.gov/system/files/documents/2025-03/wotus_notice_march2025.pdf
- Joint guidance on continuous surface connection: https://www.epa.gov/system/files/documents/2025-03/2025cscguidance.pdf
- Public fact sheet: https://www.epa.gov/system/files/documents/2025-11/public_factsheet_wotus_nprm.pdf
What These Definition Changes Could Mean for Projects
A helpful way to think about this proposal is that the EPA is tightening the measuring tape.
Some water features that were previously evaluated conservatively as potentially regulated may now fall outside federal jurisdiction if they clearly lack a continuous surface water connection.
At the same time, clearer definitions mean there is less room for interpretation. That can be helpful, but it also means decisions need to be well supported early.
What Scout Is Watching
The result is not fewer considerations, but earlier decisions. |
State Programs Still Matter
Even if the federal definition narrows, state water requirements do not automatically narrow with it.
This is particularly relevant for California projects, including large transportation and infrastructure work.
What This Could Mean for NEPA Planning
Changes to the federal definition of regulated waters can influence how water resources are addressed in NEPA documents. Clearer jurisdictional lines may reduce federal permitting in some cases, but they also place greater importance on early site understanding and documentation. For planners, this can affect analysis scope, agency coordination, and schedule assumptions, even when no federal water permit is ultimately required.
Scout’s Take
From our perspective, this proposal is less about deregulation and more about shifting when risk shows up.
Some issues may fall out of the federal process, but others move earlier into planning, field work, and coordination with state programs. Teams that plan early can take advantage of that shift. Teams that assume fewer federal requirements mean fewer considerations may still face surprises.
Scout will continue watching how this rule evolves and how it is applied in practice, particularly where federal planning and state requirements intersect.
For EPA’s announcement on the proposal, see:
https://www.epa.gov/newsreleases/administrator-zeldin-announces-epa-will-revise-waters-united-states-rule
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