The federal Clean Water Act requires that stormwater discharges from certain types of facilities be authorized under stormwater discharge permits. The goal of the stormwater permits program is to reduce the amount of pollutants entering streams, lakes and rivers as a result of runoff from residential, commercial and industrial areas. The original 1990 regulation covered municipal (i.e., publicly-owned) storm sewer systems for municipalities over 100,000 population. The regulation was expanded in 1999 to include smaller municipalities as well. This expansion of the program is referred to as Phase II.
