Flood Control

Many of the newer areas outside Chicago have a more desirable "separated" sewer system — one where rainfall flows into a separate stormwater system rather than mixing with sewage. This doesn't mean, however, that flooding is not a problem. Because the entire Chicagoland area was originally flat marshland, rainwater does not drain off easily. Continued development of the area aggravates the problem. Where open lands and pastures once dotted the landscape, now there are shopping centers, factories and expressways with their miles of asphalt and cement, leaving no place for the stormwater to flow but into streams and creeks already swollen from the rain.

The Metropolitan Water Reclamation District, in cooperation with the U.S. Soil Conservation Service and state and local municipalities, has built 28 stormwater reservoirs along small tributaries throughout the Cook County area. Six more reservoirs are planned to catch the overflow, retain the stormwater and help prevent overbank flooding. When the water levels in the streams subside, the water from the reservoirs is gradually pumped back into the streams. Unlike the combined sewered areas, no treatment of the stormwater is necessary since it has not come into contact with sewage. In dry weather, many of these reservoirs are used by local communities as parks, ball fields and picnic areas.

TARP