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7 Line Line Extension Facts

  • The 7 Line Line is the only line that intersects 18 out of 24 subways lines in the subway system.
  • The new 34th Street station at 11th Avenue is projected to be the busiest single station in New York City.
  • Will extend the 7 Line line by 1.5 miles.
  • The new station will be air tempered, and will be several degrees cooler than the outside summer air.
  • The new 7 Line line station will be the only station with 2 high rise inclined elevators, and will bring passengers 80ft below ground.
sas alignment map

When the 7 Line Line Extension opens in 2014 it will bring the Flushing Line to 34th Street & 11th Avenue, at the heart of what will be midtown Manhattan's newest neighborhood. Construction of the 7 Line Line Extension began in December 2007 and is on schedule to open for revenue service in 2014. The subway extension will make it possible for new housing, office buildings, restaurants, entertainment and other commercial establishments to grow on the Far West Side in an area now being referred to as Hudson Yards.

The new subway terminal will improve service reliability for all riders of the 7 Line Line in Queens and Manhattan by providing additional storage space for trains. It will also provide convenient access to the adjacent development and to the Jacob Javits Convention Center.

There are a total of five above-ground work sites for the 7 Line Line Extension Project:

  • Site L (Ventilation Building) – 41st Street and Dyer Avenue
  • Site K (Ventilation Building) – 11th Avenue between 35th and 37th Streets
  • Site P (Secondary Station Entrance) – 11th Avenue between 34th and 35th Streets
  • Site J (Main Station Entrance & Ventilation Building) – 11th Avenue between 33rd and 34th Streets
  • Site A (Ventilation Building) – 11th Avenue between 25th and 26th Streets

Tunnel Boring

The 7 Line Line Subway Project utilized Tunnel Boring Machine (TBM) technology. Two TBMs were brought to the construction site in pieces. The component parts were lowered down a shaft at 11th Avenue and 26th Street, and assembled underground in a chamber that had previously been created by controlled blasting. Thereafter, each TBM followed a laser-guided path to precisely tunnel along the 7 Line Line extension’s new route to another cavern that had been blasted out of the bedrock deep below 11th Avenue between 33rd and 37th Streets, where the new 34th Station will be located. The TBMs were disassembled, pulled through the station cavern, reassembled at its north end, and each relaunched on a path that eventually took it under the Port Authority Bus Terminal.

Throughout its operation, as each TBM progressed with mining it also placed consecutive sets of concrete liner rings in its wake, to form the finished tunnel. Each of the tunnel liner rings was comprised of six pre-cast concrete segments, all perfectly matched to fit together to form the 19.5 foot diameter tunnel.

Ground Freezing

The 7 Line Line Subway Extension is considered to be the first instance of a TBM mining through a substantial length of artificially frozen earth in New York City. As the two Tunnel Boring Machines (TBM) used for this project were designed to mine through solid rock, ground freezing was employed in an area where the tunnel paths were projected to go through wet soil and rocks, not solid bedrock. The process simulated bedrock by placing steel pipes into the soft ground area, then filling them with and continually re-circulating a cold brine solution. The brine “froze” the ground, creating a solid rock-like state. To accomplish this, project personnel drilled and installed over 240 freeze pipes from 80 to 106 feet deep. The ground freezing design provided a 325 foot zone of frozen earth that the TBMs could bore through as if it were rock. This allowed the TBMs to traverse the area as planned, maintaining their proper course as well as supporting the tunnels.

The operation took about 10 weeks to reach a frozen state where mining could commence, and was kept frozen for an additional 3 months until the two TBMs had passed through the area and lined the tunnels. It is believed this was the first time in the world TBMs both mined and placed precast concrete tunnel liners in a ‘ground freeze’ area.

The Underpinning of the 8th Avenue Subway

In order to make way for the TBMs to connect with existing tail tracks from Times Square, the construction team had to underpin the 8th Avenue line at the Port Authority Bus Terminal. Underpinning is a process where the existing foundations of a structure are adjusted, sometimes being strengthened and sometimes involving the shifting of loads from existing structures to temporary or new ones. The underpinning process required excavation of rock by hand and machinery to create a space for mini piles to be installed around the existing support columns. These mini piles were then connected to steel girders to further reinforce the new support system. Once all the mini piles were installed, the load was then transferred, allowing work crews to further excavate below the subway. A final load transfer of 500 tons was placed onto a series of permanent concrete pillars that were installed to support the new foundation of the 8th Avenue subway. This work was performed at night and with minimal impact to train service.

Low Vibration Track

The new station at 34th Street and 11th Avenue will be the third station in the New York City subway system that employs low vibration tracks. These specialized tracks will provide a smoother, quieter and more comfortable ride for customers, decrease the need for track maintenance, and contribute to environmental sustainability by eliminating the use of wooden track blocks.

Continuous Welded Rail Train

A unique delivery system was set up to transport the rails from an assembly yard in Brooklyn to the 7 Line Line project site on the West Side of Manhattan. This system improved the safety and created cost savings for the track installation. Five 78 foot segments of track were welded together to form a 390 foot “stringer” which was loaded onto a special service train that transported six rails across Brooklyn, Queens, the Bronx, and Manhattan. To watch a video of this process click here.

  • 2013 – December: Mayor Michael Bloomberg rides the first train from Times Square to the new station at 34th Street & 11th Avenue.
  • 2013 – August: Project reaches 90% completion.
  • 2013 – May: Tunneling contract awarded 2013 Construction Project of the Year by NYS Society of Professional Engineers.
  • 2012 – November: Tunneling contract receives an Award of Merit at ENR Best Projects 2012 Awards.
  • 2012 – May: At 65% complete, the extension receives the installation of first set of rails.
  • 2010 – July: Second Tunnel Boring Machine breaks through at Port Authority Bus Terminal – TBM tunneling is complete.
  • 2009 – December: First Tunnel Boring Machine breaks through into 34th Street Station cavern.
  • 2009 – June: Excavation of cavern within the basement of the Port Authority Bus Terminal is complete. TBM mining commences at 26th Street and 11th Avenue.
  • 2009 – April: Archbishop Timothy Dolan blesses MTA worksite.
  • 2009 – February: First tunnel boring machine (TBM) is lowered into the shaft on the corner of 26th Street and 11th Avenue.
  • 2007 – December: Ceremony is held in Times Square marking the launch of the subway extension project.
  • 2007 – November: Project’s first construction contract is awarded.
  • 2005 – January: New York City Council approves rezoning to allow for redevelopment and extension for the 7 Line line.
  • 2004 – June: NYC Department of City Planning certifies Hudson Yards Redevelopment plan, including extension of the 7 Line subway line.
  • 2003: Proposal made for rezoning of Midtown Manhattan’s Far West Side for Hudson Yards Redevelopment, including extension of the 7 Line subway line.

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