Grand Prairie Water Commission’s Alternative Water Source Program: Providing Water to Chicago’s Southwest Suburbs

Delve Underground is providing construction inspection services for the Alternative Water Source Program AWSP-01-01 Tunnel Extension project as a member of the Stantec-CMT Team, providing design and construction engineering services for the Program. The Tunnel Extension, which began construction in May 2025, is located adjacent to the Southwest Pumping Station and Durkin Park in the City of Chicago. The project consists of a 120-foot-deep (37 m), 510-foot-long (155 m), 10-foot-diameter (3 m) rock tunnel excavated using drill-and-blast methods. Concrete secant piles were selected as initial support for the construction shaft, which will receive a cast-in-place concrete final lining. Jacked concrete carrier pipe will serve as the final lining for the tunnel. Four 5-foot-diameter pump riser shafts will be constructed near the south end of the tunnel to serve a low service pump station to be constructed under a separate contract. Michels Trenchless, Inc. is the contractor responsible for the construction of this project. The tunnel will serve as a connection between the existing City of Chicago water system and the proposed low and high service pump stations to be constructed near the south end of the site under a separate contract. This future work will also include a 4-million-gallon water storage facility/suction well to be constructed mostly below grade within nearby Durkin Park. The park area will be landscaped for recreational use after construction.

When completed, the Program improvements will be the future source of water for over 250,000 residents in the region, making GPWC Chicago’s second largest customer.

The AWSP-01-01 Tunnel Extension is the first component of the nearly $1.5B Program that will carry Lake Michigan water to six southwest suburbs of Chicago: Channahon, Crest Hill, Joliet, Minooka, Romeoville, and Shorewood. These communities joined together in 2024 to form the Grand Prairie Water Commission (GPWC), which will purchase treated Lake Michigan water from the City of Chicago under a 100-year agreement and sell it to the GPWC member communities. When completed in 2030, the Program improvements will be the future source of water for over 250,000 residents in the region, making GPWC Chicago’s second largest customer. The City of Joliet is leading the project and serves as the Commission’s Program Manager. Including the work described above, the Program consists of a total of 26 work packages. These include work packages for approximately 37 miles (60 km) of large, 60- and 66-inch-diameter (1.5 m and 1. 7 m) transmission main and 25 additional miles (40 km) of regional transmission main, 16- to 48-inch (410 to 1,220 mm), which will distribute water to the member communities. Other program elements include an intermediate pump station, two intermediate water storage facilities, water delivery structures, security and video surveillance systems, communications infrastructure, and system commissioning.

The project addresses water availability concerns facing the Commission communities. Studies of the underground sandstone aquifers currently serving the region predict they may be unable to meet the GPWC members’ projected peak water demands by as soon as 2030. Detailed studies were conducted to evaluate alternative water sources before the decision was made to purchase treated Lake Michigan water from the City of Chicago. Preliminary design for the project began in 2021. Final design began in 2022 and is continuing. Construction of the AWSP-01-01 Tunnel Extension is scheduled to be completed by the end of 2026. Water is expected to begin flowing through the new GPWC system by 2030.