Before revision: Water pollution Enactment of the 1972 Clean Water Act (CWA) required thousands of facilities to obtain permits for discharges to navigable waters, through the National Pollutant Discharge Elimination System (NPDES).
After revision: Ambient water sample collection on a lake in Nashville, TennesseeWater pollution Enactment of the 1972 Clean Water Act (CWA) required thousands of facilities to obtain permits for discharges to navigable waters, through the National Pollutant Discharge Elimination System (NPDES).