SEATTLE — Washington transportation officials and Gov. Jay Inslee on Thursday halted all digging by Seattle’s tunnel-boring machine until the contractor determines what caused a large sinkhole to form over the area where the machine was operating.
“I have great concerns regarding public safety if the contractor were to move forward without addressing the root causes of this sinkhole,” Inslee said during a news conference. “We must continue to protect the public safety.”
The sinkhole, measuring 35 feet long, 20 to 25 feet wide and 15 feet deep, appeared Tuesday night. The contractor, Seattle Tunnel Partners, filled it with concrete, according to transportation officials. Officials also cited an accident on Tuesday when a barge carrying excavated soil began to tip and dropped material into the water. The spill posed a hazard to the tunnel workers and the public, officials said in a letter to the contractor.
Transportation Secretary Lynn Peterson said they ordered the work stoppage “to ensure that the contractor has the right protocols in place to proceed with their work safely.”
The tunnel-boring machine called Bertha will not be allowed to resume until the contractor’s analysis and work plans satisfy the state’s experts, she said.
A tunnel along Seattle waterfront was the plan of choice to replace the Alaskan Way Viaduct after it was damaged in a 2001 earthquake. But Bertha broke down about two years ago and only recently resumed operations after repairs were completed.
“I want to remind everyone that replacing the viaduct is critical to public safety,” Peterson said. “The tunneling work must proceed, but it must proceed safely.”
State officials conducted a manual survey of the viaduct and found no new movement, both Peterson and Inslee said.
“I want to stress the very reason the Legislature proceeded with this project originally was to tear down the seismically vulnerable viaduct and fundamentally ensure public safety,” Inslee said.
This was the second delay this week.
Digging in the tunnel was stopped on Tuesday after a barge carrying soil that was pulled from the tunnel began to lean to one side and spilled some of its load into Elliott Bay before drifting into a nearby pier. In order to prevent damage to the conveyor system, workers released the barge from its moorage at Terminal 46. That’s when some of the soil spilled into the bay.
Tunnel excavation was put on hold while the contractor inspected the terminal and pier for damage.
The original completion date for the new Seattle tunnel was the fall of 2015. When the machine started moving again, Project Manager Chris Dixon said they’ll finish the tunneling phase by January 2017 and the double-decker highway project will open to traffic in April 2018 — almost three years late.
It’s not known how the latest work stoppage will affect those plans.
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