Water Resources Development Act 1988

The McCook Reservoir Project was authorized by Congress in 1988. Subsequent legislation modified the project to exclude the originally planned reservoir site in 1996. The 10 billion gallon reservoir will now be built from a large rock quarry on the site of the project sponsor's solids processing lagoons. The Metropolitan Water Reclamation District (MWRD) of Greater Chicago 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.

MWRD and the Assistant Secretary of the Army for Civil Works signed the Project Cooperation Agreement on May 10, 1999.  Project construction began in 2000.  Stage 1 of the reservoir, with a flood storage of 3.5 billion gallons, was completed on 31 December 2017.  It has performed according to plan, preventing millions of dollars of flood damages since commissioning. 

Stage 2 of the reservoir, with a storage volume of 6.5 billion gallons, is scheduled to be completed in 2029.  It will be built by MWRD as part of a pilot project under Section 1043 of the Water Resource Reform and Development Act of 2014.  Section 1043 provides the federal share of the project cost directly to the local sponsor.  MWRD will build the final components of the reservoir with the Corps monitoring their activities to ensure the reservoir is completed to the federal standard.  Funding in the amount of $33,820,000 was provided to MWRD in February 2019 for the pilot project.