Bertha, The Boring Machine
2:27 pm
Fri February 7, 2014

Bertha: Broken, Not Blocked, Says WSDOT

Remember that big steel pipe — eight inches wide, part of an old well?

The Washington State Department of Transportation never actually accused that pipe of blocking Bertha, but it was definitely a prime suspect.

But on Friday, WSDOT said the pipe isn’t, and never was, the problem.

“All along, there has not been an obstruction at the front of the machine,” said WSDOT project administrator Todd Trepanier.

He says investigators are now pointing the finger at two other problems. For starters, Bertha’s cutterhead got clogged with muck, though it wasn’t exactly clear why clumps of dirt might pose problems for the world's largest boring machine.

The second problem deals with Bertha’s bearing (the axle that lets the cutterhead spin), which was overheating. Workers discovered a seal that kept those parts enclosed had broken. Lubricants leaked out, friction increased and temperatures spiked.

Trepanier says the contractor has now cleaned out the cutterhead, but fixing the seal will take longer. Crews may be able to fix it in place, or they may choose to actually dig a shaft 60 feet down from the surface and make repairs.

“They will come up with how to repair or replace that seal system. They cannot give me specific facts on how long it will take them to determine what they’re going to do,” Trepanier said.

Bertha is only one-tenth of the way toward completing a 1.7-mile tunnel to replace Seattle's aging Alaskan Way viaduct. The machine has been mostly idle for two months, and there is still no word on how the delays will affect the project’s overall schedule or cost.

Video: A crew member clears away the clogs.