Thursday, May 31, 2012

East Side Access third tunnel bore complete

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On the night of May 29, crews working on the New York Metropolitan Transportation Authority's East Side Access project brought a 642-ton tunnel boring machine to a halt underneath Sunnyside Yard in Queens seven weeks ahead of schedule, completing the third of four tunnels the MTA is building in Queens.

Trains using this tunnel will be traveling eastbound from Grand Central Terminal toward Long Island. They will use it to merge onto the Long Island Rail Road mainline eastbound tracks that lead to Jamaica and Port Washington. The machine began building the tunnel on March 26, 2012.

"We are delighted to complete this important milestone," said MTA Chairman Joseph Lhota. "Each piece of the project that we bring in ahead of schedule means we can dedicate resources to those parts of the project that most need attention."

The machine that built this tunnel had earlier completed its westbound twin last December. Another tunnel boring machine completed a tunnel in February that will lead from Grand Central directly into Sunnyside Yard. The production rates of these tunnel boring machines have generally been higher than expected, notes the MTA.

Digging in soft earth in Queens is unlike tunneling in Manhattan bedrock. The machines in Queens build the concrete tunnel walls as they progress, giving the tunnels shape and strength at the same time that they excavate the ground from beneath railroad tracks. In digging this eastbound tunnel, the machine installed 441 precast, segmented concrete rings. It excavated 875,169 cubic feet of soil over nine weeks as it built the 2,200-foot-long, 22.5-foot diameter tunnel.

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