Chicago digs deep to better manage stormwater
The $194.5 million Calumet Tunnel, part of the Calumet Tunnel System in Chicago’s southern suburbs, was recently completed more than a year ahead of schedule.
A joint venture including Kenny Construction, Wheeling, Ill. (lead contractor); Kiewit Construction, Omaha Neb.; and Shea Construction, Walnut, Calif., built the 11.6-mile tunnel in a project for the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC).
The Calumet Tunnel System is one of four legs of the MWRDGC’s Tunnel and Reservoir Plan (TARP) begun in the 1970s and projected to end within the next decade.
Commonly known as Deep Tunnell the plan is the nucleus of the area’s wastewater transference and storage system, designed to control pollution and flooding caused by CSOs in the city and its 51 suburbs, an area covering 375 square miles.
At completion, it will benefit nearly four million people, many of whom have dealt repeatedly with pollution and flooded basements as a result of backed-up sewage and stormwater.
Deep Tunnel, a product of city, county and state efforts, is a system of cavernous tunnels up to 340 feet deep that will intercept stormwater over-flow and channel it to multi-billion gallon storage reservoirs underground. After storms subside, the reservoirs and tunnels can be pumped dry and the water cleaned and discharged into the lake.
“This project was started because we have a system that, when it rains heavily, allows water to wind up in Lake Michigan and in the basements,” says Frank Dalton, the water district’s retired general manager and the originator of TARP.
“In Chicago, there is a law that does not allow pollution in Lake Michigan at any time. The only way you can carry out that mandate is to build a second river system, if you will, and that’s really what Deep Tunnel is all about.”
One of the biggest challenges of tunneling in the city was how to make headway without blasting. Municipal authorities wanted to reduce disruptions in residential areas but also specified a need for tunnels with an unprecedented 35-foot diameter.
Tunnels of this size had never been bored because there were no tunnel boring machines (TBMs) large enough to do the job. On the first TARP project in the late `70s, Kenny shut down preliminary drilling for a month and brought in experts from the Colorado School of Mines to reconfigure existing TBMs for the task, thus eliminating the need for blasting.
The construction company’s effort to keep residents updated on tunneling progress was another unique aspect of the project. Representatives frequently went door-to-door in communities around the Calumet project to inform residents of the project’s status. The MWRDGC now requires all TARP contractors to make similar efforts. After completion of the Calumet Tunnel System, work began on the Des Plaines leg, taking Deep Tunnel one step closer to its ultimate goal. The success of the project in the elimination of flooding will help rid the Chicago area of an historical nemesis.