New problem prevents Bertha from tunneling again

Contractors in Seattle have once again shut down the tunneling machine Bertha because of a new problem.

The world’s largest boring machine moved forward two feet this week after a seven week shutdown. That allowed work to resume on another concrete tunnel ring.

But during that brief mining operation, crews with the contractor, Seattle Tunnel Partners, noticed above-normal temperature readings in parts of the machine.

“The machine began to have some of its internal sensors, which I’ve referred to in the past as warning lights, show that temperatures were reaching a point where it was prudent to stop,” said Todd Trepanier, project administrator for the Washington State Department of Transportation.

On Wednesday, Bertha moved another two feet and the higher temperature readings persisted.

WSDOT said that Bertha will remain shut down over the next week as the state and its tunnel contractors consult with an outside expert to figure out what to do next.

“This is not unique, this is not expressive of some sort of overall concern with the machine, this is what happens with these type of tunneling machines, specifically in the takeoff, launching period,” said Trepanier.

Bertha is just more than 1,000 feet along the course of a planned 1.7-mile tunnel as a replacement for the Alaskan Way Viaduct on the Seattle waterfront.

Contractors still cannot identify the issues that led to the initial shutdown in December, but Trepanier said nothing is blocking Bertha’s path.