The Clean Water Act’s (“CWA”) principal jurisdictional element, i.e., the term “waters of the United States,” is at the fore of the debate over the proper reach of federal environmental law. Under CWA Section 404(a), any person engaging in any activity which results in the “discharge of dredged or fill material into the navigable waters” must obtain a permit from the U.S. Army Corps of Engineers (“Corps”). The term “navigable waters” is defined broadly by statute to mean all “waters of the United States.” The Corps has further defined this term by regulation to include “[a]ll other waters such as intrastate lakes, rivers, streams (including intermittent streams), mudflats, sandflats, wetlands, sloughs, prairie potholes, wet meadows, play lakes, or natural ponds, the use, degradation or destruction of which could affect interstate or foreign commerce including any such waters.” “Waters of the United States” is defined to include even “tributaries” of these waters and “wetlands adjacent to [them]” (other than waters that are themselves wetlands).