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March 21, 2012 at 10:44 AM

Tunnel machine finally breaks through early Wednesday at Capitol Hill Station

Three stills from the pit. (Courtesy of Sound Transit)

Sound Transit’s tunnel-boring machine “Togo” finally broke through into the Capitol Hill Station pit just after 4 a.m. Wednesday, completing its two-mile trip from Husky Stadium.

The 21.5-foot diameter rotary drill moved at less than a snail’s pace for the last several feet. The tunnel crew reduced the pressure at the face of the machine, and made more cutting rotations, to avoid breaking the concrete north wall, said spokesman Bruce Gray.  The breakthrough came about seven hours later than Sound Transit predicted.

In the last two hours, the machine had to wait until a couple more sets of concrete rings could be fastened in the rear. These rings, which form the permanent tube, give the cylindrical device a footing so it can push itself forward. The screeches of steel cutting tools sounded tantalizingly close.

Finally, a few die-hard transit and contractor staff let out a whoop when the machine knocked over a thin disc in the wall, said Gray.  At about 7:30 a.m., about eight or 10 workers crawled out through the cutter head and stopped to take pictures. “It’s great to see the people running these incredible machines take a moment to celebrate their accomplishment,” Gray said.

Here is Sound Transit video on the tunneling machine coming through the station wall:

A second machine, “Balto,” is excavating a parallel tube and is due to arrive in two to three weeks. The grinders are named after a pair of huskies who delivered serum to avert a diphtheria epidemic in Nome, Alaska, in 1925.  They will both be lifted out by crane after Balto arrives.  Another machine is digging between Capitol Hill Station and the downtown transit tunnel.

So far, there has been no damage to the 88-year-old Capitol Building, across the street, where owner Franklin Tseng has worried that soil may settle and cause cracking.

Train service from Westlake Station to the new Capitol Hill and UW stations is scheduled to start in September 2016. The $1,9 billion, three-mile extension is forecast to eventually serve 70,000 riders a day.

Another event is this Saturday at 11 a.m., when a huge portrait of the late Cal Anderson, the state’s first openly gay legislator, will be dedicated here. It will be mounted on a construction-site wall and moved when the project is finished.

Comments | More in General news, Traffic & Transit | Topics: boring, light rail, Sound Transit

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