Following the wet weather events, the stored flows can be conveyed, at controlled rates, to the WRPs for full treatment. These excess flows previously would have resulted in both overflows into the waterways and eventually backups in the local sewer systems. The storage capacity of the reservoirs also will promote the full utilization of the conveyance capacity of the tunnels and shafts, which in turn results in optimizing the conveyance capacity of the existing sewer systems. Therefore pollution control is further enhanced by allowing for capture of a greater volume of CSOs and greatly minimizing backups in the local sewer systems. Prevents raw sewage mixed with rainwater from spilling into Lake Michigan and the Calumet River.
Helps prevent pollution of Lake Michigan from river reversals.
Provides capture and delivery of excess combined sewage from the service area to the Thornton CUP Reservoir, which will afford major flood control benefits as well as additional pollution control. The host rock for the tunnels is the Silurian dolomite which constitutes the bedrock throughout the area. The tunnels are approximately 310 feet below existing grade elevation. The top of rock projects about 80 to 100 feet below ground surface. Glacial drift and lake bed deposits overlay the bedrock.