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East Side Access: Manhattan Caverns

East Side Access: Manhattan Caverns 1266 1216 McNary Bergeron & Associates

One of the largest transportation infrastructure endeavors ever undertaken in the United States, the mega project will provide new Long Island Rail Road service to Manhattan’s East Side with an eight-track expansion beneath Grand Central Terminal.

GRAND CENTRAL TERMINAL IS NOT wanting for superlatives. Host to more than 750,000 visitors and commuters each day, the station is the largest hub for train traffic in the world. Now, it can add one more accolade as the epicenter of the East Side Access (ESA) project, a more than $ 10 billion endeavor that is the largest project ever undertaken by the Metropolitan Transportation Authority, not to mention one of the largest transportation mega projects in the country. With congestion on the MTA’s Long Island Rail Road (LIAR) lines common, especially during morning and evening rush hours, the project will add a new LIAR terminal within Grand Central Terminal (GC1), increasing  rail capacity into Manhattan by nearly 50%.

Manhattan Caverns Construction

 

The project also promises to save LIRA travelers to Manhattan’s East Side up to 40 minutes of commuting time a day, touting a “one-seat ride” connection into GCT from Long Island and Queens. Starting with new tunnel connections from the Harold Interlockingsection of Sunnyside Yard, the project will connect the LIRR Main Line and Port Washington Branch to the 63rd Street Tunnel under the East River. Hard-rock tunnel boring machines have tunneled deep under Midtown Manhattan from the 63rd Street tunnel’s lower level at Second Avenue to a new LIAR concourse beneath the exist­ing lower level of GCT. Below that, two new terminal caverns each have an upper and lower level, adding eight new tracks for incoming trains. To connect with GCT’s lower level, a new passenger concourse within the footprint of the existing Madison Yard will include escalator, elevator, and stair connections to GTC’s dining concourse and the former arrivals waiting room, along with connections to 45th and 47th street cross-passages. When completed in 2022, the entire East Side Access project will serve an estimated 162,000 customers each day. The project’s completion will also free up LIAR tracks into Penn Station, allowing trains from the MTA Metro-North Railroad’s New Haven Line access to Penn Station through Queens. A Penn Station Access project will construct four new stations in the East Bronx, which will also significantly cut travel times to and from Manhattan.

Manhattan Caverns Construction

Will 150 prime construction contracts to date, the ESA project is a who’s who of infrastructure experts. Roles traditionally held by an architect and structural and mechanical engineer are encompassed by the role of General Engineering Consultant, a tri-venture of Parsons Brinckerhoff (now named WSP USA), Parsons Corp., and STY. Overall construction management falls under the role of Program Management Consultant, held by AECOM; a Consultant Construction Management team, a joint venture of Jacobs and Li Ro, provides additional construction management support. Early in 2016, the MTA awarded the final major contract for the project’s Manhattan Caverns to  civil and building construction company Tutor Perini Corporation. The contract will transform two enor­mous 1, 143-foot-long caverns carved out of solid rock into the new terminal station 100 feet beneath GCT. The work encompasses more than 12 miles of track work from Queens to Manhattan, as well as sta­tion platforms, elevators, escalators, and staircases to carry customers to and from the underground station, and all architectural finishes throughout the cav­erns-in renderings, these are depicted as stainless steel wall panels, modular metal ceilings, and stone flooring. When the project is complete, the caverns will hold 2,774 individual precast concrete elements including beams, deck panels, platform walls, and slabs installed by Tutor Perini. The new station’s plenum, designed to contain and ventilate smoke if necessary, has been designed with post-tensioned precast wall panels in lieu of a traditional structural steel framing system, so the project’s structural steel elements are largely used to construct elevator shafts, escalator trusses, and stairs.

Manhattan Caverns Construction“People say structural steel is good because it saves time; precast is the same way,” explained Terrence Flynn, vice president of engineering for Tutor Perini’s Civil Group on a tour of the site last spring. The precast concrete fabricator, Schuylerville, New York-based The Fort Miller Co., Inc., was able to homogenize the camber of many of the elements, ultimately relying on only eight molds to form the Manhattan caverns’ precast members. Pieces are cast with special embeds to make crane picks safer. Fort Miller also invested a significant amount of effort to perfect the precast fiber mix, balancing  a formula that would meet structural requirements while allowing for an exposed architectural finish in the completed LJRR mezzanines.

In addition to these design considerations, careful phasing was required to make work in the caverns as efficient as possible. From storage in Fort Miller’s yard, precast elements were trucked and staged as needed at storage yards in Long Island City, then driven into the cavern on a designated rubber-tire route (along which train tracks will lie in the future) on the same flatbeds used for ground transportation to avoid double-handling of the elements. Maneuvering the flatbed trucks within the tunnels and caverns posed its own challenge and had to be carefully coordinated due to constraints including duct-bench clearances, shoring, elevator pits, and overhead cantilevers.

Within each cavern, a 400,000-pound telescopic Liebherr LTR1220 crawler crane is used to pick each precast piece from the flatbed and place it in its final location. (The crane itself was brought into the cavern in pieces on 10 flatbeds and assembled in place; it will be dismantled and driven out the same way.) The project teams developed a sequencing pattern to allow the crane to complete installation of both the upper- and mezzanine-level beams and deck panels from the lower track level.

Manhattan Caverns ConstructionWith years of work ahead before the project  alleviates Manhattan commutes for many LJRR cus­tomers, members of the public can take heart that  some of the project’s benefits have already been  realized. The MTA has opened 50th Street Commons,  a pocket park between Park and Madison Avenues,  and a new entrance to Grand Central from within  245 Park Avenue, offering direct access to the terminal from points east of Lexington Avenue and north of 47th Street. And though out of sight for the hundreds of thousands of commuters, the caverns below their hurrying feet are transforming rapidly into the next chapter of Grand Central’s importance  to the growth and development of the city around it.

Article by, Metals in Construction Winter 2018