The 1972 Clean Water Act (CWA) is a landmark piece of legislation that protects American waters from pollutants and discharges. To regulate pollution discharges, the drafters of the CWA created a legal framework, the National Pollutant Discharge Elimination System (NPDES), that requires agencies to obtain an NPDES permit for pollution discharges that originate “from a point source” such as pipes or man-made ditches and enter certain bodies of water, i.e. navigable waters and surface water bodies termed “waters of the United States.” However, the definitions of “point source” and “waters of the United States” in the CWA have proven too vague and have thus been the source of much litigation.