Storm water discharges are generated by precipitation and runoff from land, pavements, building rooftops and other surfaces. Storm water runoff accumulates pollutants such as oil and grease, chemicals, nutrients, metals, and bacteria as it travels across land. Heavy precipitation or snowmelt can also cause sewer overflows which, in turn, may lead to contamination of water sources with untreated human and industrial waste, toxic materials, and other debris. EPA controls storm water and sewer overflow discharges through its National Pollutant Discharge Elimination System. NPDES provides guidanceto municipalities and state and federal permitting authorities on how to meet stormwater pollution control goals as flexibly and cost-effectively as possible.

Recommended EPA Web pages

• Office of Wastewater Management: NPDES Storm Water Program
  Provides information about the NPDES storm water program.
• National Pollutant Discharge Elimination System (NPDES)
  The National Pollutant Discharge Elimination System permit program controls water pollution by regulating point sources that discharge pollutants into waters of the United States.