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Second Avenue Subway, New York, NY


Work is under way on Phase I of the Second Avenue Subway, a 1.5-mile (2.4-kilometer) section between 96th Street and 63rd Street. In subsequent phases of the project, the line will be extended south to Lower Manhattan and north to 125th Street.

WSP USA is leading a team that is providing construction management services.

Much of the two-track line will be built using tunnel boring technology with cut-and-cover used at the 96th Street station locations. Mining is being used on two station caverns at 86th and 72nd streets and portions that are too short to make tunnel boring cost-effective. The geology of the Upper East Side of Manhattan poses challenges for the team because of its hills and valleys, Manhattan schist, a mixture of unpredictable and variable sands and silts, and fault lines.

Work has been taking place in several locations along Second Avenue. At 92nd Street, a TBM launch box was excavated; blasting was also utilized to excavate the tunnel. Nearby utilities and buildings—some more than 100 years old—required extreme care. In addition, the renovation of the existing 63rd Street/Lexington Ave station is underway. The renovation of this station, built in the 1970s, will allow the new Second Avenue Subway to tie into the existing transit system.

During construction, at least four lanes remain open to traffic and efforts are made to maintain access to businesses and residences. Structural and ground improvement techniques are used to minimize ground settlement and to preserve the structural integrity of various facilities, including utility lines, buildings, tunnels, and ramps.