Wednesday, April 10, 2013

All's quiet (sort of) beneath Grand Central

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After two years and one month of blasting, New York's Metropolitan Transportation Authority announced Tuesday that sandhogs working on the East Side Access project have concluded more than 2,400 controlled explosions under Grand Central Terminal in the building of two caverns 160 feet below the streets where eight tracks for Long Island Rail Road trains will be laid.

"This is a very significant milestone for the East Side Access project," said Dr. Michael Horodniceanu, president of MTA Capital Construction. "The caverns are essentially now fully excavated. Much work remains to be done to build the platforms and tracks, and finish what is currently raw, cave-like space. But we now have a fully built shell in which all future work will take place."

Each blast was overseen by an FDNY-licensed blaster. To conduct a blast, teams of sandhogs drill hundreds of holes measuring 11⁄2 inches in diameter into the mica-inflected granite schist that forms the bedrock of Midtown Manhattan.

Together, the holes are loaded with 200 to 500 pounds of an explosive powder known as Emulex. After the sandhogs clear into a safe area, the Blaster-in-Charge issues a warning – "fire in the hole!" – and triggers the blast.