New Milestone for No. 7 Subway Extension Project
The first of two 1,000 ton tunnel boring machines has completed its 4,661 foot run and has reached the chamber adjacent to the current terminus for the No. 7 train underneath 42nd Street. This marks a major milestone in the $2.1 billion project that will extend the No. 7 line to 34th Street and will support the growth of an emerging community on the West Side. The project is funded by the City of New York and managed by the MTA.
The tunnel boring machine (TBM) broke through into 200 ft. x 50 ft. x 40 ft. deep receiving chamber just below the Port Authority Bus Terminal in close proximity to the bus terminal foundation and utilities, as well as the 8th Avenue Subway Line. This is where the new tunnels will connect with the existing No. 7 Line terminus at Times Square.
The second TBM will break through and reach the chamber by the end of July. Together, the TBMs have travelled approximately 8,600 feet out of a total 9,388 feet, over 90 percent of their journey. The TBMs will be partially disassembled here and backed up to where they started tunneling at 26th Street and 11th Avenue where they will be lifted out of the shaft.
The receiving chamber under the bus terminal was excavated by controlled drill and blast in 2009. Through coordination and cooperation with the Port Authority, the 24-hour construction operation was completed in six months instead of 2-3 years as originally planned. The work was coordinated in a way that minimized disruption to the bus terminal and the traveling public, and was completed without a single complaint from the public.
The TBMs were launched in the summer of 2009 from an underground assembly chamber located at 26th Street. As the machines mine, they place pre-cast concrete lining rings along the excavated tunnel, making up the permanent liner of the finished tunnel.
Tunneling north from 34th Street presented unique challenges, as the tunnels run under Amtrak/NJ TRANSIT tunnels, tunnels to the former New York Central Line, the Lincoln Tunnel and the Port Authority Bus Terminal and ramps.
Once tunneling is complete, 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.