Capping years of construction – and nearly a century of anticipation – New York City’s Second Avenue Subway officially opened to the public on New Year’s Day this past weekend. This first section, known as Phase 1, runs from East 63rd Street to East 96th Street connects with midtown Manhattan and beyond.
For the Skanska USA crews who dug the tunnels, set the tracks and installed the switches that run the trains which will move an estimated 200,000 people a day, it was a moment of great satisfaction and pride. But creating the first new subway line in a century was hardly easy.
A Complicated Project
It was in the early 1900s, when horse-drawn carriages and electric trolleys clogged the streets of New York City, that the idea for a Second Avenue Subway was first proposed. For decades, it was a project that was on-again, off-again, until about ten years ago.
“We looked at this back in 2007 and it was nothing—it was just rock,” said Skanska USA Civil Vice President of Operations Gary Almeraris.
The scope of the project was immense: boring two new subway tunnels 33 city blocks long that included accommodation for three new stations and the miles of connections – water, sewer, electrical, utility and even traffic signal wiring – that ran along and through it. The new 86th Street Station alone called for the excavation of 450,000 tons of rock underneath a densely populated neighborhood filled with residents and local businesses as well as cars, trucks, buses and pedestrians.
Three separate Skanska JV teams – S3 Tunnel Connectors (Skanska Schiavone Shea), STJV (Skanska Traylor Brothers) and CSJV (Comstock Skanska) – worked together to complete different pieces of the project simultaneously to meet multiple deadlines.
In one delicate operation, the S3 Tunnel Connectors team performing the tunnel boring needed to coordinate with another (non-Skanska) joint venture team that was excavating the 72nd Street cavern at the same time, directly above them.
“It was very laborious work,” notes Project Manager Alaeden Jlelaty. “We worked around the clock, three shifts. We had a few days where we exceeded 100-foot penetrations a day. And some days we did not move more than a fraction of a foot.”
Bringing Innovation Below Ground
Excavations for the 86th Street station added another Herculean task: removing 450,000 tons of material in order to create an enormous subterranean “launch box” or starting point where the tunnel boring machine (TBM) could be assembled and start its work.
Executive Vice President Mike Viggiano explains, “We engineered a special underground support system for a 30-story residential tower in order to safely excavate the foundation of the building to create a space for an escalator at the corner of 83rd Street, for an entrance to the subway station.” The team also developed a “muck handling system” that moved between 50 and 60 buckets of rock, with a weight equivalent to 23 cars, each day, while minimizing dust and noise.
Even the tunnel boring processes were completely different: while one tunnel went through predictably hard Manhattan schist (rock), the East tunnel path traversed a sloppy, messy material filled with water and soil, making it almost impossible to dig a clean path. “We did something really cool – we froze the ground,” says Viggiano. “Our team drilled pipes into the ground and filled it with chilled brine to harden the soil and made it act like rock. That process took about four months and gave us a safe, solid structure for the project.”
A pair of videos produced by the American Society of Mechanical Engineers explains more about the process that Skanska USA crews undertook to create the line, including the creation of the “launch box” and how freezing the ground and the tunnel boring machine (TBM) worked.
Skanska’s final contract as part of the Second Avenue Subway Phase One program was a joint venture with Comstock Electric to supply and install all the running rail, third rail power, signal and communication systems that enable trains to operate from the tie-in at 63rd Street and Lexington Avenue through the new Stations at 72nd, 86th and 96th on Second Avenue.
A Subway for the Next 100 Years
For now, the line is an extension of the Q line, but when the full run of the line is complete, it will be branded the T train (following the New York Metropolitan Transportation Authority’s convention of lettered and numbered lines) and comprise a total of 16 stations, running eight and a half miles.
Building the Second Avenue Subway (called a “once in a lifetime project” by Jlelaty) safely and effectively with minimal disruption to hundreds of thousands of people who live and work on the Upper East Side is something of which our teams are immensely proud – and is a project 100 years in the making.