Viaduct Project
4:11 pm
Fri January 3, 2014

What's Blocking Bertha? Probably An 8-Inch Steel Pipe

A glimpse of the steel pipe burrowing into Bertha.
Credit WSDOT Photo

An 8-inch-wide steel pipe.

That’s what is likely blocking Bertha, the boring machine creating a tunnel through downtown Seattle to replace the Alaskan Way Viaduct.

Officials say the steel pipe is protruding from one of the openings in machine’s cutterhead. The Washington State Department of Transportation had inserted the pipe, a well casing, 12 years ago in 2002 after the 2001 Nisqually earthquake. Their aim was to better understand how groundwater flows.

“This pipe may be wound up or obstructing the front of the machine or inside the machine in some manner that’s making it more difficult for the machine to excavate," said Matt Preedy of WSDOT.

According to a WSDOT statement, “The location of this pipe was included in the reference materials in the contract.”

Chris Dixon of Seattle Tunneling Partners said they’re looking at ways to remove the steel pipe before tunneling resumes.

“We’re looking at what the best combination of those options are, primarily from a worker safety standpoint and also with respect to time considerations,” Dixon said.

The tunneling machine was stopped on Dec. 6. Over the holidays, Seattle Tunneling Partners, the contractor, drilled 17 exploratory holes near the front of the machine to diagnose the problem. Four of the holes met resistance.

WSDOT said it’s too early to estimate the cost of the one-month delay.

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