McCormick Place West Stormwater Tunnel
As part of Clark's 2.2 million square-foot expansion to the McCormick Place Convention Center, Atkinson constructed a stormwater outfall tunnel from the new facility to nearby Lake Michigan.
The 4,000-foot-long, 12-foot-diameter stormwater tunnel was designed to reduce the impact on the existing, century-old stormwater sewers and create more water resources for Lake Michigan. It directs runoff from the Convention Center's 61.8-acre roof and can handle runoff of 497 cubic feet per second. As part of the project, Atkinson also constructed a seven-foot-diameter, 200-foot-deep drop shaft and a 20-foot-diameter, 235-foot-deep outlet shaft. The project team used a Tunnel Boring Machine during excavation, as well as drill and blast techniques.
The Metropolitan Pier and Exposition Authority (MPEA) initially considered traditional stormwater management alternatives but decided to pursue a "green" approach to stormwater management to complement other environmentally sensitive design features at McCormick Place. This stormwater conveyance system carries clean rain water from the convention center roof to Lake Michigan, thereby diverting as much as 55 million gallons of stormwater from the City's combined sewer system each year.