Sound Transit to pay $43M to UW for light-rail tunnel vibration

Sound Transit to pay $43M to UW for light-rail tunnel vibration

Credit: KING

"Brenda" the tunnel boring machine is set to dig the transit tunnel from Northgate to Husky Stadium.

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by Associated Press

KING5.com

Posted on May 8, 2014 at 12:42 PM

SEATTLE -- Sound Transit is ready to pay the University of Washington $43 million to mitigate interference from vibrations caused by the construction of a light-rail tunnel from the university to the Northgate area of Seattle.

The money would move some labs with sensitive equipment such as electron microscopes that would be affected by the vibrations or electromagnetic interference.

The UW Board of Regents was scheduled to vote on the $43 million agreement Thursday, and the Sound Transit board will vote in two weeks, The Seattle Times reported.

The money would help pay for an addition to the Molecular Engineering building, which was designed to protect instruments from interference.

The $43 million in mitigation was about what transit-agency officials expected to pay, Sound Transit spokesman Bruce Gray said.

“Given the importance of what goes on in the campus and in these labs, we don’t feel like it’s out of line,” he said.

The payment to the university will be about 2 percent of the overall $2.1 billion construction cost to bring light rail from Husky Stadium to Northgate. Tunnel boring is about to begin at Northgate. Two machines will bore south to Husky Stadium, arriving in early- to mid-2016, Gray said.

The segment that goes through the University District will be about 80 feet below ground, and it will go still deeper—about 140 feet below ground—as it travels across campus, he said.

At first, the university was concerned primarily with vibrations, but Sound Transit “has done a wonderful job of finding the latest technology” to reduce ground vibrations, said Richard Chapman, the UW’s associate vice president for capital projects.

That technology includes train tracks built on slabs of concrete that sit on big rubber doughnuts at the bottom of the tunnel, a kind of track known as a floating-slab track.

Electromagnetic interference, however, remained a concern.

Four buildings on campus, adjacent to the train line, house a variety of sensitive equipment, including electron microscopes, which are “really, really, really high resolution—so when the trains come by, they generate a magnetic field, and that distorts the imaging, and you get bad results,” Chapman said.

The buildings that could be affected are Wilcox Hall, Roberts Hall, the Mechanical Engineering Building and the Engineering Annex, all on the southeast side of campus.

Research and related activities that take place in those buildings would be moved into a newly constructed addition to the Molecular Engineering building. The building was designed from the beginning to house sensitive instruments, and it has an unusually large foundation to block vibrations and electromagnetic interference, Chapman said.
 

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