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March 13, 2014 at 3:18 PM

Soil near Bertha to be searched for artifacts

Before contractors dig a pit to repair the front end of  the Highway 99 tunnel machine, a grid of 60 narrow test holes will be drilled there to check for historic artifacts.

The probing will take about one week, said Steve Archer, cultural resources specialist for the Washington State Department of Transportation (WSDOT).  Archer doesn’t necessarily expect to find objects in the four-inch-wide holes, but said scientists will look at soil layers for clues as to where human activity occurred — anything between 10,000 years ago and 1950.

Bearing parts being assembled in Osaka, Japan. (Photo via WSDOT)

Bertha’s main bearing parts, in a photo taken in Osaka, Japan, before the digger was shipped to Seattle. (Photo via WSDOT)

If the tests come up empty, there would be no effect on Seattle Tunnel Partners’ (STP) timeline to drill a 120-foot-deep vault to repair the damaged main bearing, with a restart goal of Sept. 1.

Previously in work zones around Sodo and South Lake Union, archaeologists have not found significant Native American objects, Archer said. But if the new search comes up with a find, then “we’re going to have that conversation, after we know what we’re looking at,” Archer said in a midday conference call with reporters.

He said the state has offered to share information with the Tulalip, Muckleshoot, Suquamish, Snoqualmie and Duwamish tribes.

In other developments:

  • The state has canceled its plan to recruit a team of international experts to help figure out what stopped the machine known as Bertha on Dec. 6, and give advice for a restart.  WSDOT said it found it difficult to locate experts willing to get involved. But Matt Preedy, deputy project administrator, said the main reason is that with the project’s two existing oversight panels, there’s enough expertise available already.  Another complication is that the state might wind up taking on financial risk if it meddles too much in STP’s strategy. But on that point, Preedy said, “I don’t really have anything to speculate on that.”
  • The deep rescue pit to fix Bertha will be circular rather than square, Preedy said. This is because an arc shape is stronger to resist pressure from soil or groundwater. Therefore, STP would need less internal bracing, which leaves more space inside the vault for heavy equipment to move, Preedy said.  STP submitted a draft plan that is being reviewed by WSDOT this week, Preedy said.  A full repair plan from Hitachi, the machine’s manufacturer, is now expected near the end of March, he said.

The world-record 57.3-foot-diameter tunnel drill is stranded near the corner of South Main Street and waterfront Alaskan Way South.

Comments | More in General news, Traffic & Transit | Topics: bertha, Highway 99 tunnel


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