Stormwater runoff occurs when precipitation from rain or snowmelt flows over the ground. Impervious surfaces like driveways, sidewalks, and streets prevent stormwater runoff from naturally soaking into the ground. These discharges often contain pollutants in quantities that could adversely affect water quality.
Federal regulations require permits for stormwater discharges associated with industrial activity, construction projects (disturbing one or more acre of land) and Municipal Separate Storm Sewer Systems (MS4s). These permits require controls to reduce the transport of pollutants in storm water to waters of the United States.
Discharges to Groundwater