Bertha document describes early hours of tunneling stoppage

by: Graham Johnson Updated:


SEATTLE, Wash. -  A week after project leaders announced the Highway 99 tunnel boring machine known as Bertha is overheating, a brief report obtained by KIRO 7 through a public records request provides new insight into the early hours of the crisis.

A Washington State Department of Transportation Tunnel Quality Verifier Report dated Dec. 7, 2013 said the machine shut down several times "due to high temperature at the main bearing."

The report describes grease leaking from a swivel joint and spraying out of an articulation joint.

The report says: "Still unable to advance machine. All shift spent trying to move forward with little success."

It was written one day after engineers decided to stop Bertha when the machine encountered unusual resistance.

Days earlier, Bertha had chewed through a steel well casing.

That triggered a work stoppage that while crews prepared for inspections of the excavation chamber to look for anything that might be blocking the machine.

Those January inspections found nothing substantial.

Last week, the machine advanced 4 feet over two days during a test run.

Engineers stopped Bertha when it overheated again.

The contractor has been investigating.

State officials are also consulting experts to figure out why Bertha is overheating.

They said temperatures in the excavation chamber reached 140 degrees, as much as twice the normal range.

Last week, WSDOT project administrator Todd Trepanier said the overheating is related to rotation of the cutterhead and was "not expressive of some sort of overall concern with the machine."

Bertha is the world's largest tunnel boring machine.

WSDOT officials said some problems are expected with cutting-edge technology and it takes time to work through them.