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We all know the Second Avenue Subway project will be very costly. But we didn't know that the MTA was thinking about leaving the 300-foot tunnel boring machines underground when the project is done. The NY Sun reports that abandoning the $15-20 million machines may be "more efficient and cost-effective" rather than hauling them out. Apparently there's a precedent for this: The TBMs used for the Chunnel excavation were left there (however, other U.S. cities that have used TBMs aren't sure if theirs were left underground).

MTA Capital Construction president Mysore Nagraja says whether the machine will be left in the tunnel is up to the contractor. And, to know more about subway excavation than you thought you would ever know, here's the Sun's explanation of TBMs:

The tunnel-boring machine, which drills through rock without destroying the streetscape, is the cleanest method for tunnel excavation. In the past, subway tunnels have been excavated by dynamite blasting, or a method known as "cut-and-cover," in which temporary trenches are dug into streets during construction and then covered up when the project is completed.

Tunnel boring machines were used to dig the 63rd Street tunnel about 30 years ago, where the F and the V lines now pass through. That machine was not abandoned underground because the tunnel was located close to the water, Mr. Nagaraja said.

Well, we thought it was fascinating. You can learn more about the Second Avenue Subway at the MTA's Capital Construction site.

2007_01_btrainfire.jpgIn other subway news, the Daily News reports that the MTA screwed up during the August evacuations of subway trains on the Manhattan Bridge. There was a tunnel fire, and apparently dispatchers let trains continue through, in spite of the fire and smoke conditions! Also, the FDNY didn't tell the Transit Authority they were evacuating passengers, so the third rail was still on during evacuations for seven minutes. Oh, and apparently one motorman had "repeatedly radioed alerts about the fire to dispatchers as early as [10-15 minutes before the other trains hit the fire], but the dispatchers later said they didn't hear the calls."

And a man whose arm was severed when hit by a train on Monday night is still unconscious. amNew York reports that William Santiago was in the tunnel along the A/C/E line between 50th and 59th Streets for some unknown reason when a train hit him. The operator tried to brake, but Santiago was still hit. A station agent said it was gruesome and "After they took him away they were still looking for body parts."