Stormwater runoff from streets, lawns, parking lots, construction sites, industrial facilities and other impervious surfaces occurs as a result of precipitation events (for example, rain water or melted snow). The stormwater runoff may enter surface waters directly or through natural and constructed channel systems. Activities occurring in developed and urban areas contaminate stormwater runoff with pollutants such as automobile oil, grease, metals, sediment, bacteria from animal waste, nutrients and pesticides, as well as deposits from airborne pollutants.
Unmanaged stormwater can cause erosion and flooding. It also can carry excess nutrients, sediment and other contaminants into rivers and streams. Properly managed stormwater can recharge groundwater and protect land and streams from erosion, flooding and pollutants.
As authorized under the State Water Control Law and the federal Clean Water Act, the Virginia Pollutant Discharge Elimination System (VPDES) permitting program regulates point source pollution. “Point source” is defined by the U.S. Environmental Protection Agency as “a source of pollution that can be attributed to a specific physical location – usually an identifiable, "end-of-pipe ‘point." This includes stormwater discharges from:
- Construction activities
- Industrial discharges
“MS4” - is shorthand for a municipal separate storm sewer system. Publicly owned systems such as storm drains, pipes, ditches or swales that collect or move water to surface waters must obtain permit coverage and develop a stormwater management program.
Construction - Coverage under a state permit may be required to discharge stormwater from a construction activity. In addition, local governments may manage their own stormwater management permit programs, which are separate from the state permit program and from local land disturbance permits.
During construction, a separate permit may be required for erosion and sediment control. These land disturbance permits are issued by localities as part of their erosion and sediment control programs as authorized by the Virginia Stormwater Management Act. DEQ periodically conducts reviews of these local erosion and sediment control programs.
Industrial discharges - Discharges of stormwater associated with industrial sites also are required to obtain permit coverage. The industrial stormwater permit includes management practices and monitoring requirements necessary to protect the quality of the waters receiving the stormwater discharges.
Stormwater runoff that is not confined to a single point source is considered nonpoint source pollution. One of the main ways of controlling nonpoint source pollution is through erosion and sediment control.