Cutter head for NYC's Second Avenue subway's TBM arrives

By Richard High30 April 2010

The main components of the Metropolitan Transit Authority (MTA) of New York City's new Second Avenue Subway TBM (Tunnel Boring Machine), including the 200-ton (182 tonne) cutter head, have been delivered to the project's Launch Box.

Once assembled, the TBM will begin boring the western tunnel for the new two-track line. Boring is scheduled to commence in May.

The total length of the TBM plus the trailing gear which contains the mechanical and electrical equipment that powers the cutter head is 450 ft (137 m). The cutter head has 44 rotating discs and is the vital piece of the TBM that will drill and excavate the approximately 7700 ft (2347 m) long tunnels.

The Launch Box, which extends from just south of 92nd Street to 96th Street along Second Avenue and is approximately 815 ft (248.5 m) long by an average of 63 ft (19.2 m) wide and 56 ft (17 m) deep, forms the shell of the new 96th Street Station.

This is also where the machine will be assembled and launched from one of two starter tunnels in May. Excavation of the Launch Box began in June 2009 using a combination of controlled blasting and mechanical methods. In total, 117000 yd3 (89500 m3) of rock and soil were removed.

The Second Avenue Subway, which will reduce overcrowding and delays on the Lexington Avenue line, is being constructed in phases. Phase I will providing service from 96th Street to 63rd Street as an extension of the Q train, three new ADA-accessible stations along Second Avenue at 96th, 86th and 72nd Streets, and new entrances to the existing Lexington Av/63 Street Station at 63rd Street and Third Avenue.

Construction of Phase I began in April 2007. When complete in December 2016, it will serve 213000 commuters daily currently using other subways, buses, taxis or cars and decrease over-crowding on the adjacent Lexington Avenue Line by as much as -13%, or -23500 passengers on an average weekday.

It will also reduce travel times by up to -10 minutes or more (up to -27%) for those travelling from the east.

The Second Ave Subway TBM was originally manufactured by The Robbins Company about 30 years ago. It was first used to dig the MTA's 63rd Street Tunnel in the late 1970's and has been used on at least four other projects.

The machine has been reconditioned and was rebuilt in Newark, New Jersey at contractor Schiavone's yard, where it was assembled, tested and then disassembled for shipment to the site. The TBM was most recently used on the Fall River CSO Project in Fall River, Massachusetts.

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