June 2026 – Update to Definition of Waters of the United States

Author: Paloma Hernandez

The definition of “Waters of the United States” (WOTUS) has undergone substantial change over time, with the most recent proposal to provide clarity in November 2025. Following a public comment period that closed on January 5, 2026, it became apparent to the United States Environmental Protection Agency (U.S. EPA) that a principal concern among stakeholders was the absence of a clear definition of what constitutes a “wet season.”

This issue originated from the Sackett v. Environmental Protection Agency (2023) Supreme Court ruling, in which the Supreme Court ruled in favor of Sackett, declining to classify a portion of their property as wetlands on the grounds that those wetlands lacked a “continuous surface connection” to navigable waters. It is within this framework that the concept of the “wet season” arises; a continuous surface connection refers to water that is present on a “relatively permanent” basis, flowing continuously year-round or, at a minimum, during the “wet season.”

The 2025 proposed redefinition of WOTUS gave rise to considerable public debate surrounding the “wet season” concept, as it raised several unresolved questions including how the “wet season” should be defined, how the regulation would apply to streams exhibiting only intermittent flow throughout the year, and, more broadly, what the change would mean for the long-term durability of the law.

On June 30, 2026, U.S. EPA submitted to the Office of Management and Budget a supplement to its November 2025 proposed WOTUS rule. According to records maintained by the Office of Information and Regulatory Affairs, this document is expected to address matters including “continuous surface connections,” the “relatively permanent” standard, and the distinction between jurisdictional and non-jurisdictional ditches. The stated objective is to render the applicable rules clearer, simpler, and more durable over time. By aligning the definition of WOTUS with the Sackett decision, the proposed change is intended to clarify implementation of the Clean Water Act (CWA) programs applicable to wetlands.

Potential Impact on Industries and Stakeholders

While the proposed WOTUS revision touches several Clean Water Act programs, its effect on existing permitted dischargers is expected to be minimal. The more significant consequence is likely to be a reduction in the overall number of permits issued going forward. By some estimates, the revised definition would remove federal protection from roughly 81% of wetland acreage nationwide, which would translate into fewer Section 404 permits and correspondingly less required mitigation.

For project owners whose sites contain wetlands falling within this gray area, the revised rule and definition could meaningfully alter the permitting strategy. Features previously assumed to be jurisdictional may no longer require federal authorization or mitigation, while ambiguity around the “relatively permanent” standard could complicate things. However, State regulations should still be considered even as this proposed redefinition becomes active. For example, in Pennsylvania, the Department of Environmental Protection regulates all wetlands under Chapter 105, regardless of federal jurisdictional status, which could mean a Chapter 105 permit and associated mitigation may still be required even where a Section 404 permit is not. Project teams should therefore coordinate with both the Army Corps and State regulators as early as they are able to confirm jurisdictional determinations under each framework, as well as the appropriate permitting pathway.

From a compliance perspective, this ruling may not materially affect wastewater, stormwater, or other National Pollutant Discharge Elimination System (NPDES) programs that also discharge to a WOTUS. That said, as the new rule provides greater clarity, we will be better positioned to evaluate its broader implications.

Current Stage and Timeline

This proposed redefinition is at the Final Rule Stage; unless the agency specifically reopens the comment period or issues a supplemental proposal, the formal public comment period was closed on January 5th, 2026. Issuance of the Final Rule is anticipated in late summer of this year.

If you need support with CWA compliance in Pennsylvania and/or the surrounding states, please reach out to Paloma Hernandez at phernandez@all4inc.com or 215-839-8964.