The now-damaged green cutter head was lowered into place before the Bertha tunnel-boring machine began operations on the Seattle waterfront in 2013. Credit: WSDOT
Bertha won't go full bore on her digging until probably March 2015 — about six months behind the previously estimated restart target. All this means that Bertha could be stuck for a total 16 months.
"We are disappointed. … with the delays associated with restart," said Todd Trepanier, the Alaskan Way Viaduct program administrator for the Washington State Department of Transportation. He added, "These delays are not what people have been looking forward to."
He made his remarks as state officials and its contractor, Seattle Tunnel Partners, on the waterfront tunneling project unveiled new details of their plans to repair and restart the giant tunnel-boring machine. An STP official gave a hopeful assessment.
This delay could bump the tunnel's opening back by four to five months. However, STP is trying to keep to the current November 2016 opening date by working on the tunnel's operations facilities and other sub-projects that were originally scheduled to be tackled toward the end of the project.
The tunnel boring machine dubbed "Bertha" has been stalled since early December due to seals breaking in the cutter head, with grit and sand getting into the main bearing. The full restart had been scheduled for this September, but that has been delayed by another six months, the state and STP announced Monday. Broad hints had surfaced in recent weeks that the September restart target would not be achieved. The tunnel will eventually replace the aging Alaskan Way Viaduct, which could fail in a major earthquake. Bertha is currently about 1,000 feet along the 9,300-foot tunnel path, which begins in SoDo and ends in South Lake Union.
Bertha is currently 60 feet underground just west of the viaduct near Pier 48. The master plan is to dig a 83-foot diameter shaft that will go 120 feet into the ground in front of the boring machine and then move Bertha into the shaft. The cutter head section with broken seals and main bearing — weighing several hundred tons — would then be lifted out of the shaft and replaced. Originally, the seals were considered the chief problem. But then the main bearing's issues showed up.
The actual shaft digging cannot begin into until a ring of 75 boreholes are dug around the shaft site. Then concrete will be injected to form a barrier to prevent water form seeping in. Meanwhile, the site is being studied to determine if anything archaeologically significant will be found in the shaft area.
The actual excavating is tentatively scheduled to begin in late July and to finish in September. Removal of the cutter head is expected to begin in October. It will be replaced by a new cutter head that manufacturer Hitachi Zosen Corp. is currently storing in Japan. Testing of the tunnel-boring machine is set for February 2015, with actual tunneling expected to resume in late March 2015.
"It's a whole series of challenges and complex activities. … We want the machine to be in 100 percent tip-top condition so we don't have a repeat (of the 16-month delay)," Chris Dixon, Seattle Tunnel Partners project manager said.
Dixon said it is unknown how the six-month tunneling delay will affect the project's cost. Trepanier said the state's contract with STP appears to guard the extra costs from being transferred to the taxpayers. With progress on the actual tunneling impossible, the project has recently laid off roughly 60 employees, but still has 300 people working.
Referring to the March 2015 goal, Dixon said, "Internally at STP, we're fairly confident we can beat this date." STP may have a financial incentive for limiting the delay to 16 months or even trying to get Bertha back in service early. The state has taken the position that problems with the tunnel won't allow STP to bill taxpayers for cost overruns.
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