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Second Avenue Subway tunnelling complete

Tunnelling has been declared complete on the much delayed Second Avenue Subway project in New York.

A tunnel boring machine (TBM) has reached the Lexington Ave-63rd St. station, breaking into the existing New York Subway tunnel and marking the end of tunnelling on the $4.45bn (£2.8bn) project. Concrete tunnel lining will now be installed.

The TBM began its journey in March and completed the northbound tunnel after making a tight, westerly curve into the existing 63rd Street Station. The 485t, 137m long TBM used a 6.7m diameter cutterhead to bore the 2.37km long tunnel, averaging approximately 18m a day. The average depth of the tunnel is 21m.

The TBM began boring the project’s 2.2km long southbound tunnel in May 2010 before being disassembled and pulled back to the launch box to start the northbound tunnel. It will now take approximately three weeks to partially disassemble and pull back the TBM through the tunnel by locomotive. Phase I of the Second Avenue Subway will be completed in December 2016. It will reduce overcrowding on the Lexington Avenue Line by 13%.

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