Six months before Bertha resumes digging

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by MANUEL VALDES Associated Press and KING 5 News

KING5.com

Posted on February 28, 2014 at 1:57 PM

Updated Friday, Feb 28 at 6:21 PM

SEATTLE  -- A machine digging a highway tunnel underneath Seattle that has sat idle since December likely won't begin working again for another six months, an official with the contractor said Friday.

But Seattle Tunnel Partners project manager Chris Dixon said that estimate is "slightly optimistic."

The machine, dubbed Bertha, stopped working about 1,000 feet into the 1.7-mile Highway 99 tunnel. If the six month estimate holds, that means Bertha will be stopped for nine months.

"This isn't the time to accelerate things or take short cuts," Dixon told reporters Friday.

Dixon said the Japanese company that built Bertha will finalize a report on their options to access Bertha in about 10 days. Those options have been narrowed to three shafts of different sizes that will allow crews to reach the machine. Depending on the size of the shaft, crews will be able to take apart sections of Bertha and work on them either at the bottom of the shaft or at the street surface. Those are the details the team from Hitachi-Zosen will be exploring.

  • Option 1: (Narrowest shaft) Moving pieces forward and working on them vertically.
  • Option 2: Bringing pieces up to the surface to work on them horizontally.
  • Option 3: (Widest shaft) Laying pieces horizontally at the bottom of the shaft.

Building and designing a shaft to access Bertha will take about 2 months and then repairs would have to take place, Dixon added. The shaft will be about 120 feet deep and be located just south of Main Street.

The seals surround the main bearing are broken and have to repaired or replaced.

The completed tunnel will allow the state to tear down the Alaskan Way Viaduct, the 60-year-old double-decker highway along the Seattle waterfront that is in danger of collapsing in an earthquake.

The viaduct will be closed this weekend for a routine inspection. Monitors have already found the viaduct settled nearly half an inch near the tunnel-boring machine. The Transportation Department said that was expected and the viaduct is safe, for now.

Dixon added that the state got lucky the machine got struck where it did because if it would have stopped further along, building a shaft would not have been a possibility.

He added that the scope of the problem is not fully known yet, and thus the costs of repairs has not been estimated.

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