First Phase of 7 Line Subway Extension Construction Complete
In partnership with New York City, the MTA is extending the 7 line to support the growth of an emerging community on the Far West Side. The $2.1 billion project, funded by the City and managed by the MTA, will help transform the Hudson Yards vicinity into a vibrant 24-hour neighborhood.
The MTA recently announced that it has reached a major milestone with the completion of the first phase of this vital transit-oriented, economic development project. The second of two 1,000-ton tunnel boring machines broke through the future 34th Street Station cavern wall in December 2009 completing the train storage section. A tunnel boring machine (TBM) is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock. The two TBMs mined a combined 2,900 feet from their starting point at 26th Street under 11th Avenue.
The TBMs were launched in the summer of 2009 from an underground assembly chamber located at 26th Street. The first 300 feet of tunneling was complicated by a section of soft ground between 27th and 28th Streets that required a technique called "ground freeze" to reinforce the ground, allowing the machines to pass through as if it were solid rock. As the tunnel boring machines mine, they place pre-cast concrete lining rings along the excavated tunnel, making up the permanent liner of the finished tunnel. While the new service will terminate at the new 34th Street station, the tunnels continue to 25th Street to allow for the storage of trains.
One tunnel boring machine has already started mining north of the station cavern toward 42nd Street while the other is being pulled through the cavern and will begin mining this week. Tunneling north from 34th Street also presents unique challenges, as track will run under the 8th Avenue Subway, Amtrak/NJ TRANSIT tunnels, tunnels to the former New York Central Line, the Lincoln Tunnel and the Port Authority Bus Terminal and ramps. Excavation and underpinning of the 8th Avenue Subway line is underway to allow the new tunnels to tie into the existing 7 Line tail tracks at Times Square.
Tunneling will be completed in the spring of 2010, when work will commence on station entrances and finishes, as well as support facilities such as ventilation and traction power substations. Customers will be able to take advantage of the new service in December 2013 as scheduled.