• Navigable waters are waters of the United States, including the territorial seas; however, since 2001, the definition of “waters of the United States” has come into question and been revised several times.

Section 112.2 provides a definition of “navigable waters.” It says, “Navigable waters means waters of the United States, including the territorial seas, as defined in § 120.2 ...” That sounds simple, but the Environmental Protection Agency (EPA) has had a difficult time nailing down the meaning of “waters of the United States,” also known as WOTUS, since a 2001 U.S. Supreme Court decision, Solid Waste Agency of Northern Cook County v. U.S. Army Corps of Engineers, and later court decisions.

Each EPA administration has attempted to set the scope of waters that are subject to the Clean Water Act, and each attempt has faced lawsuits. The definition of WOTUS has been revised several times. What’s more, the agency has proposed another iteration on November 20, 2025, which has yet to be finalized.

For the current definition, facility owners/operators will want to review the latest 40 CFR 112.2, 120.1, and 120.2.