Traylor Bros., Inc. leads the second largest contract in the system of tunnels being constructed to connect the Long Island Railroad (LIRR) commuter lines in Queens to Grand Central Station in Manhattan.
Presently, the line only connects with Penn Station; the additional 24 peak-hour LIRR trains into Grand Central will represent a capacity increase of about 30,500 new peak-hour seats, meeting the future needs of Long Islanders to reach Manhattan jobs. Included in the project are four 19.5-foot-inner-diameter tunnels totaling approximately 10,500 feet in length; three reception pits; and three shafts that include cross-passages for emergency access and ventilation.
The tunnels, comparatively shallow, are located beneath Amtrak’s Sunnyside Yard and LIRR’s Harold Interlocking. The project will connect the existing 63rd Street tunnel, using the open-cut structure created by the Queens Open-Cut Excavation contract, to the mainline and Port Washington Branch LIRR tracks. Two 22-feet-6-inch Herrenknecht slurry tunnel boring machines (TBMs) are being used in the difficult geological conditions, which include mixed face, soft ground, random cobbles and boulders, hard rock, and dense glacial till.
The most challenging aspect of the project is dealing with the highly variable ground conditions, which can result in settlement beneath the active tracks of the railyard. The team is controlling settlement by implementation of the slurry TBM system. Additionally, the team is working with the New York City Department of Transportation for traffic diversion plans and permits for working in the streets. Thus far there have been minimal impacts to the area.