HNTB is playing a critical role in controlling stormwater at O’Hare International Airport as the Chicago Department of Aviation embarks on a major capital improvement program to expand and modernize the airport’s facilities.

Acting as the program’s lead civil and engineer-of-record, HNTB designed and is currently overseeing construction of two tunnels comprised of more than 10,000-feet of storm trunk sewer systems. The two tunnel systems, both considered to be enabling projects critical to the overall success of the program, divert flows from existing storm sewers to an existing downstream pump station.

The Tunnels

Located more than 40-feet below ground, the two systems include a 2,800-foot long, nine-foot diameter tunnel and an 8,000-foot long, 14.5-foot diameter tunnel. Delivered by Construction Manager at Risk (CMAR), the tunnels proved to be the ideal solution for this busy location.

The stormwater tunnels are being excavated using tunnel boring machines that minimize construction disruption, addressing CDA’s requirement of keeping taxiways, runways and terminal aprons fully operational during construction. Launched and retrieved from the shaft locations, the TBMs can install most of the tunnel systems virtually unnoticed by passengers, airlines and other airport stakeholders.

By understanding the ground behavior and subsurface risks, HNTB was able to mitigate potential impacts associated with underground construction. Implementing a comprehensive and through subsurface investigation, HNTB was able to identify and quantify the subsurface risks as well as specify the proper methodology for tunnel construction. Ultimately, this better prepares the contractors for anticipated conditions during tunnel construction and significantly reduces impacts to the CDA’s infrastructure and their operations.

As a result of HNTB’s design and tunneling expertise, CDA can confidently move forward on its plan to expand and renovate O’Hare, without impacting airport operations.

Location: Chicago, IL

Client: Chicago Department of Aviation