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Fixing Seattle Tunneling Machine to Take Months, Says Contracting Team

The machine has been mostly idle for two months and is only one-tenth of the way toward completing a 1.7-mi. tunnel.

Sat March 08, 2014 - West Edition
Construction Equipment Guide

SEATTLE (AP) The contracting team hired to dig a highway tunnel under downtown Seattle told the Washington state Transportation Department on Feb. 10 that it will take months to fix broken seals on the world’s largest tunneling machine, the Transportation Department said.

Seattle Tunnel Partners is working with Hitachi Zosen, the machine’s manufacturer, to determine how best to fix the broken seals surrounding the main bearing of the machine called “Bertha,’’ which is 60 ft. (18 m) underground, Transportation officials said in a statement.

The contractor is looking at accessing the area through the back of the machine or by drilling a shaft in front of it.

“Either way, this process will take months,’’ the Transportation Department said.

The machine has been mostly idle for two months and is only one-tenth of the way toward completing a 1.7-mi. (2.7 km) tunnel. The tunnel will carry Highway 99 traffic and allow the removal of the aging Alaskan Way Viaduct along the Seattle waterfront.

Chris Dixon, director of Seattle Tunnel Partners, told The Seattle Times that his team is considering “four or five options’’ for a front-end approach.

Once the shaft was dug, the 630-ton (571.5 t) cutter head would be detached and lifted using a crane, the newspaper said.

Dixon said a decision hasn’t been made yet. Depending on what inspections show, the contractor might be able to deliver the parts through the back of the machine.

On Feb. 7, the Transportation Department said inspections conducted in January found that many of the machine’s cutter-head openings were clogged with dirt and other things. Transportation officials also announced that the seal system protecting Bertha’s main bearing was damaged. This was revealed after “higher-than-normal heat sensor readings’’ appeared.

Seattle Tunnel Partners “has not yet fully determined the cause of the seal problems and, to date, they have not shown any evidence that suggests the state or taxpayers will be responsible for cost overruns associated with these repairs,” transportation officials said Feb. 10.

“We have requested and expect detailed plans on how the repairs will be made and how STP can recover lost time on the tunneling project,’’ the state said.

The project is budgeted at $1.4 billion. The total viaduct replacement is estimated to be a $3.1 billion project. The tunnel project is supposed to be finished in late 2015.

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