In an internal draft of new guidance designed to clarify their jurisdiction under the Clean Water Act, the Environmental Protection Agency and the Corps of Engineers explain the regulated community can expect that “the number of waters found to be subject to CWA jurisdiction will increase significantly[.]” The agencies have been refining their interpretation of “waters of the United States” subject to Clean Water Act jurisdiction since the Supreme Court decided Solid Waste Agency of Northern Cook County (SWANCC) v. US Army Corps of Engineers and U.S. v. Rapanos. The guidance clarifies what the agencies regard as a “significant nexus” as discussed in Justice Kennedy’s opinion in Rapanos. The draft also suggests the agencies will seek to revisit limits imposed on their jurisdiction under SWANCC to regulate so-called “other waters” including intrastate wetlands, mudflats, prairie potholes and the like through future regulatory action. In the meantime, the agencies will make case-by-case determinations of their jurisdiction over such waters. While the guidance does not constitute a formal rule, the agencies have indicated they would open the guidance to public comment.