Metropolitan Washington Airports Authority (MWAA), as a result of a recent competitive solicitation, awarded Atkinson/Clark/Shea, a joint venture, a contract to build the East Domestic Automated People Mover (APM) Tunnels and Stations at Washington Dulles International Airport. Construction of the APM will allow rapid passenger transportation from the main terminal to proposed APM stations that will be located at the airport’s midfield concourses.

Work includes construction of inner and outer domestic APM tunnels using the cut-and-cover method, New Austrian Tunneling Method (NATM), and Tunnel Boring Machine (TBM) method; and construction of a Tier One Station, a Tier Three Station Shell, an inner Spur Track using the cut-and-cover method and a tunnel portal at the vehicle maintenance facility.

This contract also includes the MEP fit-out of the tunnel stations as well as installation of the Emergency Radio Supplemental Radiating System (SRS) for handling emergency communications with MWAA, Loudoun and Fairfax counties.

Clark and Atkinson, a Clark subsidiary headquartered outside of Denver, will work with the J.F. Shea Company, of Walnut, CA, on this heavy civil project to self-perform significant portions of the work.

In total, traditional cut and cover construction will encompass more than 6,775 ft. (2,065 m) of rock excavation averaging a depth of 50 ft. (15 m). This construction will allow for the concrete work involved in casting the twin box tunnels and two stations. Steel rock bolts and shotcrete facing will provide the excavation support to the in-situ materials. This portion of the contract represents the largest shotcrete job in the history of Clark.

The diameter of the TBM tunnel is approximately 20 ft. (6 m) and consists of more than 2,100 ft. (640 m) of twin bore length. Two custom machines, known as moles, will bore through solid rock, utilizing multiple cutting wheels mounted into a face shield. Precast concrete wall lining segments are mechanically put into place by the mole as it continues to move forward.

Located on the northern end of the project, the NATM tunnels consist of 800 ft. (244 m) of excavated tunnel. In the NATM method, the tunnel is mined utilizing more conventional excavation equipment that must dig through the tunnel face in 3- to 5-ft. “bites.”

On-site engineers determine the actual excavation sequences and drift lengths. The tunnel team utilized this method for the recently completed trolley station at San Diego State University.

The Tier One station will incorporate finishes and MEP systems similar to those found in the local Metro subway system. The Tier Three station will be finished to the shell stage, as it will be used as a future station for a yet-to-be-constructed concourse.

The Washington office of HNTB and HOK worked together as the architects, engineers and planners for the project.

Washington Dulles International Airport is situated in Fairfax and Loudon counties in Virginia, 26 mi. west of downtown Washington, D.C. In 2003, the facility served more than 16.9 million passengers, with more than 4 million traveling on international flights.

This project is the second competitively awarded to the team in 2004. Earlier in June, Clark/Shea began work on the Dulles West APM tunnels.

For more information, visit www.clarkconstruction.com.

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