Stormwater is the runoff that results from precipitation. As this water flows over construction sites, farm fields, lawns, driveways, parking lots, and streets, it picks up sediment, nutrients, bacteria, metals, pesticides, and other pollutants. Unlike sanitary sewers that go to a treatment plant, most stormwater is discharged directly to local water bodies.
Increasing amounts of impervious surfaces in urban areas, such as rooftops, driveways, parking lots, and streets, decreases the ability of the water to soak into the ground, thus increasing the amount of stormwater. More stormwater places more demands on the city’s stormwater infrastructure.