Q: What is stormwater run-off?

A: Stormwater run-off is the water that flows off roofs, driveways, parking lots, streets, and other hard surfaces during a rain event. 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 water supply.

Q: What problems does it cause?

A: Stormwater can carry harmful non—point 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 run-off. The rest is absorbed or evaporates. In urban areas, up to 55% of rainfall can become stromwater run-off.

Q: Why are the stormwater and sanitary sewer systems separate?

A: Unlike wastewater, 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 wastewater would be very expensive.

Q: What is non-point source pollution?

A: Non-point 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 non-point source pollutants include: fertilizers, pesticides, sediments, oils, salts, trace metals, and litter. They come from farms, yards, roofs, construction sites, automobiles and streets.

Q: What is an impervious surface?

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