Santa Susana

Surface Water

Managing Stormwater

What is storm water?

Storm water is precipitation (either rain or snowfall) that is prevented from being naturally filtered into the earth's surface by impervious surfaces such as driveways, streets, and parking lots. Soil that is saturated after a heavy rain can also prevent storm water from being absorbed into the ground.

What pollutants are commonly found in storm water and why are they harmful?1

Pollutants such as oil and grease, pesticides, fertilizers, sediment, and other substances commonly found in our environment are also present in storm water run off. Polluted storm water runoff can have many adverse effects on plants, fish, animals, and people. Sediment can make it difficult or impossible for aquatic plants to grow and can destroy aquatic habitats. Excess nutrients from fertilizers can cause algae blooms. When these blooms die and decompose, they remove oxygen from the water, making it difficult for fish and other aquatic organisms to exist in water with low oxygen levels. Bacteria and other pathogens can wash into swimming areas and create health hazards, often making beach closures necessary. Household hazardous wastes like insecticides, pesticides, paint, solvents, used motor oil, and other auto fluids can also poison aquatic life. Polluted storm water often affects drinking water sources, which impacts human health and increases drinking water treatment costs.

How is storm water regulated?

The purpose of regulating storm water runoff is to prevent pollutants from reaching our rivers, lakes, and oceans. California is authorized by the United States Environmental Protection Agency (EPA) to regulate storm water discharges in California under the Clean Water Act's National Pollution Discharge Elimination System (NPDES) program. The NPDES regulations cover discharges from municipal separate storm sewer systems, certain industrial activities, and construction activities that disturb one acre or more of land. Information about these regulations and the permitting process can be found at EPA's home page for the NPDES program http://cfpub.epa.gov/npdes/index.cfm and at California's storm water home page http://www.waterboards.ca.gov/water_issues/programs/stormwater.

How is storm water run off managed?

Storm water run off can be managed by implementing Best Management Practices (BMPs). These practices can be very simple, such as ensuring the proper cleanup of an oil spill, or very complex (the installation of sophisticated filtering systems, for example). The types of BMPs implemented will depend on the type of pollutants that are being controlled.

1 Most information obtained from EPA publication "After the Storm," USEPA, 2003 (EPA 933B-03-002).