The U.S. Environmental Protection Agency (EPA) and U.S. Department of the Army have issued a supplemental proposal seeking additional public input as they work to finalize a new definition of “waters of the United States,” or WOTUS, under the Clean Water Act.

The Supplemental Notice of Proposed Rulemaking adds regulatory alternatives for consideration alongside the agencies’ November 2025 proposed rule. The effort is intended to further implement the U.S. Supreme Court’s 2023 decision in Sackett v. EPA, which narrowed the scope of waters subject to federal Clean Water Act jurisdiction.

The definition of WOTUS is significant for the stormwater sector because it helps determine which waterbodies fall under federal Clean Water Act programs and where federal permits may be required for certain activities. Waters outside federal jurisdiction may still be regulated by state, Tribal or local authorities.

EPA and the Army said the supplemental proposal will allow stakeholders to comment on a limited number of additional regulatory alternatives without eliminating options included in the original proposal. The agencies previously received more than 220,000 comments on the 2025 proposed rule. A 30-day public comment period will open once the supplemental proposal is published in the Federal Register.