Federal Requirements

Since 1972, the EPA's federal Clean Water Act has prohibited the discharge of any pollutant to waters of the United States unless the discharge is authorized by a National Pollutant Discharge Elimination System (NPDES) permit. The NPDES program is a national permit program designed to regulate point source discharges, and in 1990, the NPDES Phase I program was established to manage stormwater pollution from certain industrial and construction sites, and to large urban areas with populations greater than 100,000. In 1999, EPA adopted NPDES Phase II regulations to address stormwater discharges from sites that were not covered under Phase I. State and municipal stormwater requirements are based upon these federal regulations, and incorporate additional provisions to address the specific needs and conditions of individual watersheds.

Phase I of NPDES applies to:

• Construction sites disturbing greater than five acres
• Companies that fall in one of the eleven categories of industrial sites
• Large and medium municipalities (MS4’s) with populations of 100,000 or greater

• Construction sites disturbing one to five-acres
• Municipalities in urbanized areas not covered by Phase I, otherwise known as small MS4s.

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NPDES for MS4s
NPDES for Construction sites