Stormwater MS4 Program

Stormwater runoff is the water that flows off roofs, driveways, parking lots, streets, and other hard surfaces during rain storms. Rather than being absorbed into the ground, it pours into ditches, culverts, catch basins, and storm sewers.  It does not receive any treatment before eventually entering the community’s streams and lakes.

Stormwater can carry harmful nonpoint source pollutants, cause flooding, erode topsoil and stream banks, and destroy marine life habitats. In an area with natural ground cover, only 10% of rainwater becomes runoff. The rest is absorbed or evaporates. In urban areas, up to 55% of rainfall can become storm water runoff.

Unlike waste water, which is treated before it is released back into the environment, storm water goes directly into a community’s ponds, streams and lakes. Because stormwater comes in large amounts at unpredictable times, treating it as waste water would be very expensive

Nonpoint source pollution is water pollution that is difficult to trace to a specific discharge point. Because it comes from many diverse sources, it is hard to control. Examples of common nonpoint source pollutants include fertilizers, pesticides, sediments, oils, salts, trace metals, and litter. They come from farms, yards, roofs, construction sites, automobiles, and streets.

Any surface that does not readily absorb water and impedes the natural infiltration of water into the soil. Common examples include roofs, driveways, parking areas, sidewalks, patios, decks, tennis courts, concrete or asphalt streets, crushed stone and gravel surfaces.

For single family homes, a statistical sampling was taken using Geographical Information System (GIS) including aerial survey data. Each was measured and an average impervious surface area was determined.  For businesses and other institutions, the city measured the impervious area using aerial survey data.

Creating natural areas on your property can help reduce the quantity of stormwater runoff. Disposing of wastes properly, using the minimum amount of chemicals on your yard, and keeping your car well-maintained can reduce the amount of pollution that you add to storm water runoff.