Long before tunnel-boring machine Bertha stalled underneath Seattle because of leaky seals, it experienced a problem involving the same seals back in Japan.
When workers tested the mammoth $80 million machine before it was shipped here last April, they discovered damage to the seal system and ended up taking Bertha apart for repairs.
Now Bertha is again having problems with seals. There are indications that all seven of the machine’s outer seals may have been breached, according to the state Department of Transportation and the tunnel contractor.
Repairs will take several months in a 120-foot-deep pit that must be dug in front of the machine in wet soil along Elliott Bay.
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While Bertha is having trouble with the same seals that had to be fixed in Japan, it’s unknown whether the cause of the problem is the same, said Matt Preedy, deputy administrator for the Alaskan Way Viaduct Replacement Program with the state Department of Transportation.
“We, of course, are curious if it’s any way related to the previous situation during dry-dock testing, but I don’t want to guess,” he said in an interview last week.
It would be unusual for all of a tunnel borer’s outer seals to breach so early in its journey, Preedy said.
An expert review-panel report on the Highway 99 project, written a year ago when Bertha was still in Japan, noted that the tunnel boring machine’s builder, Hitachi-Zosen, found “a significant fault” during testing that was expected to cause delays and make it “unlikely that the TBM will be completely assembled and fully tested prior to shipping.”
Preedy said that when Bertha was being built in Japan, one of the tests performed was to turn on the motors and rotate the cutter head. That’s when testers heard a noise and took Bertha apart. They found that some parts of the machine weren’t moving properly and caused “some metal-on-metal contact and basically damaged the seal assembly for the main bearing,” Preedy said.
After discovering the problem, the manufacturer, among other actions, had to “totally repair the seal system and reassemble it and rotate it again,” he said.
The seals protect the $5 million main bearing, which enables the ring-shaped drive shaft to turn the cutter, at about one rotation per minute.
Bertha has a redundant system of seven outer seals and one inner seal with the idea that if a seal gets breached, there are several left to protect the bearing.
Preedy said it’s not uncommon for a tunnel-boring machine to have one or two seal breaches as it nears the end of a tunnel “but still have enough seals left” to complete the project.
But it is unusual for all outer seals to be breached early in its journey, he said.
“Clearly where we are right now is the tunnel-boring machine is not nearly far enough along in its drive that a contractor should attempt to continue to go, because they don’t have any seals left in the outer seal ring,” Preedy said.
Bertha’s inner seal appears to be fine.
Extent of damage unclear
Chris Dixon, director of Seattle Tunnel Partners, the group hired to build the tunnel, said last week they hadn’t determined how much damage has been done to the outer seals yet.
“There are indications that somewhere around that whole circumference where the seals are installed, that all of them might have been breached, but we won’t really know until we remove that part of the machine and fully expose all of the seals,” he said.
Dixon said there have been other tunnel projects with multiple seal failures but acknowledged it’s not common. “The right characterization would be it was something that wasn’t anticipated this early on this tunnel project,” he said.
STP is moving ahead with plans to dig a shaft in front of Bertha so the cutter head can be exposed and the seals repaired.
Once the pit is dug, the 630-ton cutter head will be detached and lifted using a crane supported by wide footings so it won’t sink into the soft waterfront soils.
After the repairs are completed and the cutter head reattached, workers will backfill the hole so the machine can resume its journey. It’s not clear how long it will take to do all that work.
Time pressure in Japan
When Bertha was still in Japan, the expert review panel noted the importance of getting the tunnel boring machine shipped to Seattle on time: “It is imperative that the TBM be loaded and shipped as scheduled to maintain the tunnel project schedule.”
That meant getting the machine components on the Jumbo Fairpartner because the next ship large enough to carry Bertha was not scheduled to be in Japan for another six months.
As it turned out, the project lost approximately one month on its schedule by the time the Jumbo Fairpartner and Bertha
made it to Seattle in April. The 41 sections were reassembled in Sodo and tested before drilling began July 30, as is routine for deep-bore tunnel projects.
The expert report said testing might have to be completed in Seattle. The report also pointed out that Seattle Tunnel Partners had a “very aggressive” schedule for tunnel completion. In an interview earlier this month, members of the review panel said they believed at the time that the schedule was doable.
Dixon said the machine was fully tested before it started tunneling.
Some tests that could have been done in either Japan or Seattle were done once the machine got here, he said. Those tests were unrelated to the seal system, Dixon said.
As far as the aggressive schedule pointed out by the expert panel, Dixon said, “I don’t see that as any kind of a contributing factor” to Bertha’s current problems.
The 1.7-mile dig
was supposed to be finished by fall 2014, and the new Highway 99 tunnel to open for traffic at the end of 2015.
The state is now gingerly backing away from its assurances the job would be done by the end of 2015.
Todd Trepanier, Highway 99 administrator for the state Department of Transportation, reminded Seattle City Council members on Monday that the state’s original requirement was to finish the tunnel by late 2016. STP, which won the state bid to build the tunnel under a $1.44 billion contract, offered to complete the project 10 months earlier in exchange for up to $25 million in early-completion incentives.
Trepanier said he has not heard STP say it will be done significantly later than Dec. 31, 2015. The drilling is almost certain to stretch beyond the October 2014 timetable, but STP could try to accelerate its follow-up work installing the double-deck roadway and utilities.
Battle over extra cost likely
Before drilling began, state officials estimated it would progress at six feet per day to start and eventually accelerate to 35 feet per day under downtown. The machine exceeded 35 feet on some of its best days this fall but has operated for only 36 days since the July 30 launch.
Bertha has traveled 1,025 feet since drilling began July 30. After a shutdown Dec. 7, the machine advanced four feet during experimental restart efforts Jan. 28-29.
When asked by Seattle City Council members Monday about the cost of delays, Trepanier said that under the design-build contract system STP is the “engineer of record” and is therefore responsible for the design risk and related delays.
“There’s been no evidence put forth by Seattle Tunnel Partners that would show that any of the cost associated with this would be borne by our agency or by the taxpayers,” he said.
Dixon, of STP, has previously said in interviews that he considers a union work stoppage in August and a pipe the machine struck in December to be state issues for which STP could potentially file a claim.
Negotiation or litigation over costs is likely.
Andrew Garber: 360-236-8268 or firstname.lastname@example.org. Twitter: @awgarber. Material from The Seattle Times archives was used in this story.