New Age

MTA Inches Toward First New Rail Line in a Half-Century

The construction work irritating drivers along the 2nd Ave. on the Upper East Side of Manhattan is just the beginning of a project the size of which New York City has not witnessed in decades. The 2nd Ave. Subway line, on which construction broke ground last spring, will add an entire new line in Manhattan running from 125th Street to the Financial District in Lower Manhattan.  The first of four phases alone, which includes tunnels from 105th St to 63rd St. and three new stations, is expected to provide over 200,000 trips daily.

Eventually, the project will include a connection from Second Avenue under 63rd St. to existing tracks for service to West Midtown and Brooklyn, and add 16 new stations.

The $16.8 billion project attracts a fair share of skepticism, and for due reason. The idea for a 2nd Ave line was first floated over 75 years ago when the East Side first experienced a boom in residential and commercial development, but the economic collapse of the Great Depression postponed it. The project came back to life, only to be put on hold again during World War I. As population grew, the need became more serious when the elevated Second Ave. train was demolished in the early 1940s, and the elevated Third Avenue train in 1956. The East Side was left with only one train - the Lexington Ave. 4,5,6 service.

In the 1960s, a plan was put forward for a two-track line from the Bronx to Lower Manhattan. Construction finally started on several segments of the tunnel - only to be suspended indefinitely during the city's 1970s financial crisis.

It wasn't until 1995 that MTA New York City Transit picked up the project again, following its Manhattan East Side Alternatives (MESA) Study under the federal Major Investment Study/Draft Environmental Impact Statement (MIS/DEIS), which came out with more than 20 alternatives to alleviate the traffic congestion on the East Side. The Second Avenue Subway, now known as SAS, an underground line running from 125th St. to the Financial District, won out overwhelmingly with everyone involved in the public review process. By 2004, DMJM Harris/Arup joint venture came out with a preliminary engineering plan.

Finally, last March, the first $337 million contract was awarded to a S3 Tunnel Construction, a joint venture of Skanska USA Civil of Whitestone, N.Y.; J.F. Shea Constructors of Walnut, Calif.; and Schiavone Construction of Secaucus, N.J. The same joint venture, incidentally, would go on to get a $1.14 billion contract for the No. 7 line extension.

“The potential shortage in manpower was one of the driving factors in the formation of the joint venture,” says Robert Nichols, vice president of estimating at Skanska USA Civil Northeast. “We felt that the ability to draw labor resources from all three companies would be a key factor in mitigating the manpower risk. We are confident that we have the manpower to execute this project.”

Last April, the project broke ground.

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Phase 1of the project includes tunnels from 105th Street and 2nd Ave. to 63rd St. and Third Ave., new stations along 2nd Ave. at 96th, 86th and 72nd Sts., and new entrances to the existing Lexington Av/63 St. Station at 63rd St. and 3rd Ave. In effect, Phase 1 will be an extension of the Q train service in Manhattan. The Q will run under 2nd Ave. between 96th and 63rd Sts., and divert west along an existing line at 63rd St. At Lexington Ave., Q riders will be able to transfer to the F train, or continue downtown under Central Park on tracks currently not used for passenger service all the way to the current northbound Q train termination point, the 57th St./7th Ave. stop.

S3 Joint Venture is working on Contract 1 of Phase 1, which includes the segment between 96th Street and 63rd Street, including 3 new stations and 1 station rehabilitation.

“Our Contract 1 is to construct the northbound running tunnels between 72nd and 92nd streets and the southbound running tunnel between 92nd and 63rd St. We’re currently in the process of relocating utilities on Second Ave., between 91st and 95th Sts., to facilitate construction of the launch box for the tunnel boring machine (TBM),” says Nichols. “We are now working on the west side of 2nd Ave. and expect to move to the East side by the middle of February. We expect to finish utility relocation by the middle or end of May. At that time we will begin slurry wall and secant pile wall construction to create the “bathtub” that we will excavate and launch the TBMs from.”

The launch box is approximately 400 ft. long x 60 ft’ wide x 65 ft. in depth.

The most challenging aspect of the first contract on phase 1 is the relocation, replacement and support of a web of utilities, including electric, gas, sewer, water, telephone,  and communication lines. The location of the project is such that there are literally four lanes of traffic running through the site.

Before the TBM is even lowered into the ground, the amount of machinery on the site is substantial. The team will use standard excavators and front-end loaders for the utility relocation. A crawler-mounted drill rig, such as Bauer BG-40 or BG-36, along with a service crane, will be used to install the secant piles. In addition, 200-ton class cranes with clamshell buckets will be used to excavate the slurry wall. For the launch box, the team will use the excavators and crawler cranes at the surface; under the decking, dozers and track loaders will be used for excavation.

“The joint venture is planning on using a main-beam hard rock tunnel boring machine to mine the running tunnels and will utilize a vertical conveyor to transport excavated rock to the surface for disposal off-site,” says Nichols. “A final decision of rail cars vs. horizontal conveyor in the tunnels has not been reached yet -- we are exploring both options.”

This January, the team completed utility relocation on the west side of 2nd Ave. and rerouted traffic to the west to begin work on the east side.

To minimize the impact on residents, businesses, utilities, and traffic, “approximately half of the 16 stations along the new 8.5-mile alignment will be mined,” according to DMJM Harris. In addition, the only visible part of the work on contract 1 will occur between 92nd and 96th Sts.

“For this contract, once the launch box is constructed, the TBM is lowered and final decking is in place, the only sign of construction above ground will be the excavated tunnel rock leaving the site,” says Nichols. “All tunneling work will be accomplished from below the road decking, with traffic above.”

“There is a TBM underneath Park Ave. 150 ft below ground,” says Mysore Nagaraja, president of MTA's Capital Construction, about the work going on for East Side Access. “There are people living and working above it - and they don't even know that we are boring underneath them. That will bet he experience on the 2nd Ave. Subway.”

The way the subway is being built today is drastically different from the 1970s. “During initial construction, all of the tunnels were constructed utilizing cut and cover (open cut) methods and would have utilized underground drilling and blasting to mine the rock tunnels,” says Nichols. The TBM will be able to do this work quicker and more efficiently. “The cut and cover sections generally utilized steel sheeting for support of excavation and timber road decking.”

This time around, slurry walls and secant piles will be used to support the road around the launch box. “This provides a more rigid ground support and a much smoother and safer road surface for the traveling public,” he says. In addition, the equipment today uses cleaner burning engines and ultra-low-sulfur fuel and emits less noise. 

Toward the end of contract 1, expected to take 40 months, the team will excavate shafts at 69th and 72nd Sts., which will then be used to construct the 72nd St. station.