The stream of rulemaking to define regulatory jurisdiction under the federal Clean Water Act took another meander on Sept. 4, 2026, when the Environmental Protection Agency and the Army Corps of Engineers issued a supplemental notice of proposed rulemaking. That proposal appeared in the Federal Register the following week. See 91 Fed. Reg. 57,284 (Sept. 9, 2026). If adopted, the proposal would limit the regulatory ambit of the Clean Water Act to traditionally navigable waters (TNW), “relatively permanent waters” (RPW) that flow or display standing water every day of the year (with limited exceptions) that are themselves connected to a TNW, and wetlands that have a surface water connection to an adjacent TNW or RPW. Wetlands that have groundwater that saturates soil in the root zone but that do not display water at their surface (either from inundation or groundwater rising) would not be subject to federal regulation. That would represent a contraction of federal jurisdiction by even more than was proposed last year. See 90 Fed. Reg. 52,498 (Nov. 20, 2025).
‘Waters of the United States’ May Shrink Even Further
