Stormwater and storm sewer system

Not all of the water generated when it rains or snows are able to be absorbed into the ground. What is left is called stormwater. As stormwater washes over roads, yards, roofs, and parking lots, it picks up pollutants such as motor oil, pet waste, fertilizer and litter. The stormwater then makes its way into storm drains and the city’s storm sewer system. Unlike the sanitary sewer system, storm sewers do not transport runoff flows to a treatment plant to remove the pollutants. The stormwater is discharged directly into creeks and streams, along with the litter and pollutants it has picked up along the way. This can lower the quality of our natural waterways and make our creeks and streams unfit for swimming and fishing and for supporting aquatic life.

Stormwater can also pose problems with flooding. When rain falls on impervious surfaces such as roads and rooftops, it cannot infiltrate into the ground, but it does concentrate and drain downhill, and as it does, it picks up speed. Without detention basins and retention ponds to temporarily hold the fast-moving stormwater, these flows would reach our creeks and streams faster than they did prior to development, which can lead to flooding in low-lying areas. The speed of the water can also create erosion, which introduces sediment pollution in our waterways and decreases the clarity and quality of our creeks and streams.