State officials say they want more information about why a sinkhole formed on the Highway 99 tunnel project before allowing Bertha to resume digging.
The state says it’s not satisfied with answers coming from Highway 99 tunnel contractors about why a sinkhole suddenly formed along the waterfront this month.
The Washington State Department of Transportation (WSDOT) requested more information before Seattle Tunnel Partners (STP) will receive written permission to restart tunnel-boring machine Bertha, which has been shut down by the state since Jan. 13.
For the delayed Highway 99 tunnel dig this means more downtime, until the sides can sort out their disagreements.
Gov. Jay Inslee and WSDOT ordered STP to suspend drilling Jan. 13, the morning after the sinkhole formed, which the contractors filled with concrete and sand. A notice by Brian Nielsen, deputy Highway 99 administrator, told builders to submit a root-cause analysis of the incident.
STP replied by urging an immediate restart. Manager Chris Dixon called the shutdown “wrongful and unjustified” in a letter, saying Bertha should be allowed to continue another 250 feet to a planned inspection stop.
Gov. Jay Inslee said he is “extremely disappointed” with the tunnel contractor, and said at a Thursday news conference that he is deferring to state engineers as to when STP has earned the right to restart.
State engineers noticed after the sinkhole formed that additional voids existed, and STP didn’t have a clear plan to deal with them, according to Inslee.
Inslee stressed the “contractual obligation to Washingtonians to drill the tunnel in the right way.” Bertha is about 250 feet away from a planned stopping point, then is scheduled to dive under the Alaskan Way Viaduct as the tunnel route proceeds downtown.
“Look, we’re going under a viaduct. It’s the only arterial right now, north-south along the waterfront. We don’t want it to go down,” Inslee told reporters.
Meetings continue this week among state tunnel-project executives, contractor managers and outside experts on the state’s strategic technical-advisory team.
Tunnel spokeswoman Laura Newborn said: “STP has told WSDOT it will submit additional information sometime this week. WSDOT and our tunnel experts reviewed the initial submittal and determined it did not sufficiently address the root causes of the incidents, nor address how STP would prevent these types of incidents from occurring in the future.”
Under the tunnel’s design-build contract, which places responsibility on the builders, the state has tried to avoid telling STP how to do its work, she said.
Thursday afternoon, an online update from the state listed five general criteria STP must meet for the suspension to be lifted, among them: “All necessary training for staff on the tunneling machine is complete.”
Dixon sent the state more than 60 pages last week, including charts showing machine and soil data, though it doesn’t blame individuals. Dixon previously told reporters the team was focused on running the cutter effectively, and its readings looked normal — but acknowledged workers weren’t making constant checks of the soil volume removed.
STP concluded it’s not possible to determine unequivocally what caused the sinkhole.
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“The potential reasons are a pre-existing void, a ground loss in the face of the [tunnel-boring machine] or a combination of both,” the report said.
Bertha’s front end was lifted last year from a deep access vault and strengthened, after the machine overheated and stalled Dec. 6, 2013. Since the repairs, it moved 190 feet until the sinkhole formed 135 feet behind the cutterhead.
A message from Tutor-Perini Corp. this month notified investors that “delays on the Alaskan Way Viaduct project in Seattle” were one reason 2015 earnings fell below expectations.
It remains to be seen who pays for which overruns, but STP has estimated the cost for repairs at $143 million.