Jurisdictional wetland

Under Section 404 of the Clean Water Act, placing fill in “waters of the United States” requires a permit from the U.S. Army Corps of Engineers. Which wetlands count as waters of the United States has changed several times; the Supreme Court’s 2023 decision in Sackett v. EPA narrowed federal reach to wetlands with a continuous surface connection to other covered waters.

Federal coverage is only part of it. Many states and counties regulate wetlands and the buffers around them on their own terms, and some do so more broadly than the federal rule.

Why it matters

A map tells you a wetland may be present. Only a field delineation by a qualified wetland scientist establishes where its boundary lies, and only the agency can say whether it is regulated. If a mapped wetland sits where you want to build, that delineation is worth ordering before you close rather than after.