Congress, in the Clean Water Act, explicitly directed the U.S. Environmental Protection Agency (EPA) and the Department of the Army (Army) to protect “navigable waters.” Section 404 of the Clean Water Act for purposes of regulating wetlands only mentions protection of “waters of the United States”, but did not define them. This caused decades of confusion and legal disagreement among those regulated by the Clean Water Act and by those who regulate the Act. This resulted in numerous lawsuits, several of which were heard by the US Supreme Court in 2001 and 2006. It has also caused delays and increased costs for those whose plans for development caused unavoidable impacts to wetlands.