A recent Environmental Law Institute (ELI ) report identifies the types of waters and wetlands that are unregulated by the U.S. Army Corp of Engineers (Corps) following Solid Waste Agency of Northern Cook County (SWANCO) v. Corps, 531 U.S. 159 (2001), and Rapanos v. United States, 547 U.S. 715 (2006), which limited federal jurisdiction. In preparing the EP A-funded report, ELI reviewed records from more than 2,500 Corps findings of no federal jurisdiction between 2008 and 2009.

According to the report, the types of waters and wetlands most often not regulated under the Clean Water Act (CW A) include (i) prairie potholes, (ii) playa lakes, (iii) headwaters, and (iv) intermittent streams. The report notes that inconsistent state and Corps district reporting makes it difficult to determine exactly how the respective agencies make decisions about jurisdictional issues. The report recommends both better recordkeeping and more consistent reporting by agencies and states to better catalog areas not currently covered by the CW A.