Proposed Rule Changes
The U.S. Environmental Protection Agency (EPA) and U.S. Army Corps of Engineers (Corps) published a proposed rule change on November 20, 2025 to revise the definition of “waters of the U.S.” (WOTUS) in the federal Clean Water Act (CWA). The revisions will affect the circumstances in which permits are needed to disturb, dredge, and/or discharge fill material into streams, wetlands, or other waters deemed federally jurisdictional. Several attempts to revise WOTUS definitions have been attempted in the past decade (2015, 2020, 2023) that have run into legal challenges. The current effective regulations are based on 2023 WOTUS definitions amended to conform with Supreme Court decisions in Sackett v. EPA (598 U.S. 651, 2023) and the Rapanos v. U.S. (547 U.S. 715, 2006) Justice Scalia ‘Plurality’ opinion.
The new rule would further codify and clarify Sackett and Rapanos standards to determine WOTUS jurisdiction currently in practice. The rule would codify the currently applied Continuous Surface Connection (CSC) test that requires WOTUS to connect to a Traditional Navigable Waterway (typically large rivers or lakes). It would also clarify that the following features cannot be used to establish a CSC unless such a feature conveys relatively permanent flow: channelized non-jurisdictional surface water feature, subterranean river, culvert, dam, tunnel, or similar artificial feature, or through a debris pile, boulder field, wetland, or similar natural feature.
The rule also proposes new changes that are the result of stakeholder input listening sessions held in April and May 2025. The most significant of these changes are:
- application of a ‘wet season’ concept to evaluate the Relatively Permanent Waters (RPW) test for federally jurisdictional streams and ditches;
- requiring wetlands to meet a new two-part test to be federally jurisdictional: 1) must abut a jurisdictional water, and 2) must have surface water at least during the wet season;
- adding a WOTUS exclusion for ditches that are constructed or excavated entirely in dry land, and codifying the definition of a ditch as ‘a constructed or excavated channel used to convey water’; and,
- adding a WOTUS exclusion for groundwater, even in circumstances where groundwater is conveyed or channelized through subsurface drainage systems.
The rule changes fall short of adding a WOTUS exclusion for stormwater management facilities, which has been a frequent topic in WOTUS regulation, especially since stormwater discharges are still deemed ineligible for the waste treatment system exclusion. WOTUS regulation of stormwater facilities will therefore be evaluated on a case-by-case basis. Waste treatment systems that receive stormwater in addition to wastewater remain eligible for the waste treatment system exclusion so long as the system continues to serve the treatment function for which it was designed.
Public comment will be accepted on the proposed rule at Regulations.gov under Docket No. EPA-HQ-OW-2025-0322-0015 until January 5, 2026. A summary of frequently asked questions is provided at this link.
Potential Practical Issues with Determining Surface Water During the Wet Season
The introduction of the ‘wet season’ term is based on regulators’ attempt to reconcile a measurable ‘bright line’ surface water duration requirement that is ‘implementable by both ordinary citizens and trained professionals’ for meeting Rapanos and Sackett court decisions that WOTUS should have standing or continuously flowing surface water at least seasonally. The proposed rule would therefore mean wetlands and streams that lack surface water for any duration during a normal wet season would not be federally jurisdictional. The surface water requirement is based on the ‘semipermanently flooded’ National Wetland Inventory (NWI) program definition which implies that surface water persists throughout the growing season in most years, but replaces growing season with wet season—although use of growing season is offered as an alternative approach for comment. Intermittent streams and portions of otherwise jurisdictional wetlands that do not have surface water continuously during the wet season may not be WOTUS. However, ambiguity of the wet season term and a lack of established methodology for determining the wet season or presence of surface water are significant concerns for a final rule-making, as demonstrated by the lengthy discussions of alternative approaches and solicitation for input on implementation methods and legal consistency.
Wet seasons vary drastically across regions and are often not consistent year-to-year, especially with variable climate and drought cycles. The rule proposes use of the University of Delaware’s Water-Budget Interactive Modeling Program (WebWIMP), a component of the Corps’ Antecedent Precipitation Tool (APT), as a primary source for identifying the wet season, but there are drawbacks to this approach. The WebWIMP and APT categorize wet season as an interpretation of average monthly water-balance metrics, estimating when precipitation exceeds evapotranspiration. In most regions of the U.S. that period generally occurs during the winter/spring seasons, and in the northern U.S. the time period to determine hydrology would be the opposite of the recommended time period (growing season) to perform wetland delineations, potentially requiring multiple visits to evaluate a stream or wetland for the Jurisdictional Determination (JD) process.
Establishing methods to document the continuous presence of surface water during the wet season may be another hurdle for a final rule. Over the past 40 years, the Corps has issued prolific research and many guidance documents on methods for making rapid field assessments of Ordinary High Water Marks (OHWM) for waterbodies, stream flow duration, and wetlands (areas with prolonged inundation or saturation near surface). These methods often use physical indicators, such as soil or vegetation patterns, as proxy data for interpreting long-term hydrologic patterns because a single point-in-time field visit may not provide a weight of evidence sufficient to support a scientifically defensible opinion for use in the regulatory review process. Although the proposed rule does not propose to invalidate these Corps-approved methods for OHWM and wetland determination, it would add a new layer of complexity by suggesting these or other methods should be used to document wet-season surface water for WOTUS JD purposes. For instance, the rule does not specify which field indicators will be acceptable to correlate surface water presence, since direct hydrologic monitoring and remotely sensed data (e.g. aerial photography) are not practical for most circumstances. Furthermore, data collected during an unusually dry period during the wet season would be confounded, leading to uncertain conclusions that might only be resolved by waiting until an area has a normal wet season. This lack of clear methodology may lead to less consistency and predictability during JD and permit review unless clarified in the final rule, if the wet season concept is applied in the final rule.
What You Can Do to Prepare for Proposed Rule Changes
Although the timing of a final rule is not yet known, here are some things you can do to prepare for the rule changes:
- Anticipate that additional hydrologic assessments during multiple seasons may be needed to collect information sufficient for Jurisdictional Determinations if getting waters declared non-WOTUS is helpful for your project schedule. CEC can help you navigate this depending on the type of impact, and which state the project is in.
- Maintain stormwater systems by removing accumulated sediment and colonizing vegetation unless specified by design and control fugitive runoff or seepage to prevent surrounding areas from meeting the definition of wetlands.
- Retain documentation (e.g. pre-construction conditions, design plans, permits, and maintenance records) for stormwater and subsurface conveyance systems. This documentation may be proof to refute jurisdictional claims in the future and prove that features were excavated in, and drain only, uplands.
If you have questions on if/how the new WOTUS rule may affect your project, contact Jonathan Farrell at 412-977-1456 or jfarrell@cecinc.com.
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