McCormick Place Stormwater Tunnel
The $882.5 million design-build West Hall Expansion contract added a fourth building to the world’s largest convention center—a 2.2 million square-foot expansion of the McCormick Place Convention Center. Under a $14 million subcontract to parent company Clark Construction Group, LLC, Atkinson constructed the stormwater outfall tunnel and three shafts to direct stormwater from the new 61.8-acre facility roof out under Lake Michigan to an outlet shaft on Northerly Island.
The design-build team designed the tunnel and shafts to accommodate a 100-year storm event with a system flow capacity for stormwater run-off of 497 cubic feet per second. The team designed and built the outfall tunnel to reduce impacts on the century-old storm sewers and to create more water resources for Lake Michigan.
Atkinson constructed the 3,450-foot-long, 12.5-foot unlined inside diameter stormwater tunnel through limestone rock using a Tunnel Boring Machine (TBM). We also drilled and blasted the three shafts and TBM starter tunnel.
The shafts consisted of a seven-foot diameter, 200-foot deep drop shaft on the convention center site, a 20-foot diameter, 235-foot deep outlet shaft on Northerly Island, and a 155-foot deep, 22-foot diameter shaft adjacent to Lake Michigan.
Atkinson also performed cutoff grouting in the shafts and tunnel, and installed four tide flex valves.