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McCook Reservoir


Water Resources Development Act 1988

Project Description:

The McCook Reservoir Project was authorized by Congress in 1988. Subsequent legislation modified the project to exclude the original reservoir site in 1996. The 10 billion gallon reservoir will now be built out of a large rock quarry on the site of the project sponsor's solids processing lagoons. The Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) is the local sponsor and will own and operate the reservoir when construction is completed. The reservoir will be built in two stages to allow the first stage to be completed and fully functioning while rock is being quarried from the Stage 2 area. Major components include an overburden cutoff wall, distribution tunnels, a main tunnel, dewatering pumps, gates, valves, hydraulic structures, aquifer protection, and an aeration system. The project helps with combined sewer (sanitary and storm) overflows that cause flooding and watercourse contamination in Chicagoland and benefits Chicago and 36 suburbs, including 1.5 million structures and 5 million people.        


Total Project Cost:   $ 638,168,000
Federal Cost:   $ 478,626,000
Non-Federal Cost:   $ 159,542,000

Current Status:

The Metropolitan Water Reclamation District and the Assistant Secretary of the Army for Civil Works signed the Project Cooperation Agreement on May 10, 1999. Project construction has been underway since 2000 and is 80 percent complete. Completed features include pumps; aquifer protection in the form of an overburden cut-off wall and a multi-stage grout curtain around the entire perimeter of the reservoir; the distribution tunnels complex; the main tunnel access shaft; Stage 1 and 2 overburden slope stabilization; Stage 1 rock wall stabilization and fabrication of the main tunnel gates.

Construction is nearing completion on the Main Tunnel and gates installation. In addition, the Final Reservoir Preparation contract, which will include the hydraulic structures in the reservoir and the aeration system, is well underway. This contract will finish Stage 1 of the reservoir ready for use at the end of 2017.  Stage 2 of the reservoir will be constructed after mining of rock in the Stage 2 area is completed in 2027. 

Project Manager

Michael Padilla