Tunnel boring machine from 20 years ago could be Bertha's needed fix

by: Graham Johnson Updated:

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SEATTLE - They called it Excalibore, the biggest tunnel boring machine on the continent.

In 1993, it began digging a critically-needed international rail tunnel beneath the St. Clair River between Sarnia, Ontario and Port Huron, Michigan. 

Then, when Excalibore was 500 feet shy of the river, it ran into trouble.

Sediment had gotten in to the seals that protected the vital main bearing, which turned the cutterhead. 

It's very similar to the problem now plaguing the tunnel machine known as Bertha, which is stuck on the Seattle waterfront. 

"Every job has a problem when you're on a major one and this wasn't any exception," said Neville Harrison, Chief Engineer for Hatch Mott MacDonald. 

He and other project leaders spoke in 1995 to filmmakers hired by Canadian National railway to document the tunnel construction.

"We had a chance to fix the machine before we reached the river and everyone felt strongly we had to do that," Mike Roach, Project Engineer Traylor & Associates told filmmakers. 

Engineers considered powering through the problem, but the risks were high.

"The last thing we wanted was any chance of the machine stopping under the river," Harrison said. 

Excalibore broke down beneath an oil refinery, with a patch of flat, unused land just ahead.

"As long as we could get there that was the place to put a shaft," Harrison said. 

It was a rescue shaft, smaller than the one crews will build for Bertha, which is also stuck early in its dig with open land above.

"Once we had misfortune of the breakdown we had the fortune of having a suitable area," Harrison said. 

When construction began on the shaft, it did not go well. 

The initial pit plan called for a basic, skeletal support structure. 

But in the soft clay, that was not enough. 

"The soil conditions were not good. It was not stable," Don Dimitrov, Supervisor of Safety for the St. Clair Tunnel Construction Company told filmmakers. 

So the shaft was re-engineered to completely replace the soil and add solid concrete walls.

That change-of-plans meant a fix first supposed to take as little as six weeks, instead took six months longer than expected.

"During the breakdown period everybody was very frustrated and morale dropped, six or seven months of going virtually nowhere," Harrison said. 

KIRO 7 asked Chris Dixon of Seattle Tunnel Partners about the shaft design problem in Sarnia. 

"We don't expect any caving in problems in the shaft," Dixon said in reference to Bertha.

In 1994, when Excalibore's pit was finished, crews drove the machine into it and disassembled the pieces. 

They lifted the giant cutting head out of the 13-story hole to examine the main bearing's seals. 

The damage was worse than they expected.

"As it turned out there was metal-to-metal contact in the TBM and we would not have been able to make it across the river," Duncan G. MacLennan, Vice-President of St. Clair Tunnel Construction Company told filmmakers in 1995. 

Parts were repaired then lowered back into the pit.

At last, Excalibore could dig again and the rest of the project went smoothly.

"We skedattled across the river in six weeks," MacLennan said.

The project was done, but nearly eight months late.

The dispute over who paid for the problems with Excalibore went on more than a decade, eventually ending up in the Supreme Court of Canada.

According to industry newsletter Tunnel Talk, the high court ordered the insurer to pay more than $30 million Canadian.