Why do our sewers overflow when it rains?
More than 100 years ago, Indianapolis built a storm sewer system to carry rainwater and melting snow away from homes, businesses and streets. When indoor plumbing came later, homeowners and business owners hooked their sewage lines to these storm sewers, combining stormwater and raw sewage into one pipe. This was common practice in many U.S. cities, especially in the Northeast and Midwest.
During dry weather, a combined sewer system works much like a separate sewer - carrying all sewage to the treatment plant for treatment. However, when it rains or snow melts, the sewer can be overloaded with incoming stormwater. When this happens, the sewers are designed to flow over internal dams in the underground pipe system and into nearby streams and rivers. Without these overflows, sewage would back up into basements and streets. Today, when building new sewer systems, we build separate sewers for stormwater and sewage.
Click here to see how our sewers work.