While work on a $3.1 billion downtown Seattle waterfront tunnel project hasn't advanced a foot since early December, a Pierce County plant producing concrete liners for that halted tunnel project is moving ahead at a normal pace.
More than 10,500 curved concrete liners are stacked outside the Encon plant in Frederickson and on a nearby site awaiting the day when the state Route 99 tunnel resumes work.
The project was halted when Bertha, the project's 7,000-ton tunnel boring machine, struck an 8-inch steel casing some 60 feet below ground and began overheating last December.
Contractors removed the casing from Bertha's path, but the 58-foot-diameter boring machine, the world's largest, continued to suffer mechanical issues with a contaminated main bearing.
The semi-circular liners are designed to be fit together to form a complete circle to define the finished tunnel's walls and to protect the bore from collapsing. The liners are fed to the boring machine which places them against the walls of the tunnel it carves as it advances.
But the contractors digging the tunnel says it won't be placing liners in the tunnel until Bertha restarts. Those contractors now are digging a pit in front of the boring machine to allow the damaged cutting head to be removed and repaired.
The boring machine's restart is expected to happen sometime next March.
When the tunnel is complete, the tunnel liners will form a 9,270-foot-long tube carrying traffic beneath downtown Seattle. The tunnel will replace the existing Alaskan Way Viaduct. That two-level viaduct was damaged in the Nisqually earthquake and doesn't meet safety standards.
While the boring is halted, the tunnel contractors said they have faith that Bertha will be repaired and the tunnel completed. That's why they decided to continue producing the liners at the Pierce County plant.
Steve Harding, business development manager for Dragados USA, one of the Seattle Tunnel Partners companies, said casting the tunnel liners at the $20-million plant continues apace.
That plant employs about 200 workers producing those liners using precision machines imported from around the world.
That production started last summer at a plant that formerly produced concrete highway products.
Lloyd Neal, project manager for the tunnel liner job, said the Frederickson plant has produced 11,967 liners to date.
About 1,500 of those liners are either already installed in the first 1,000 feet of the tunnel that Bertha dug before stalling or in storage near the tunnel project site. The remainder are stacked in rows in Frederickson.
"We never planned on storing this many liners here at the production site," said Neal, "so when we ran out of space, we had to rent more property nearby."
At peak production, the plant produced more than 100 liners daily. Now the production pace is more relaxed, said Neal, with about 60 to 70 being manufactured daily.
The production manager said he expects the job producing the 14,450 liners needed for the project to be complete by August.
Once the job is done, the machinery used to build the liners will either be stored locally or shipped to another job site.
"We work on tunnel projects internationally," said Neal, "so this plant machinery may find another use overseas."
The delay and repair of the tunneling machine is expected to cost about $125 million. The contractor and the state are now debating who should pay the extra cost.
The tunneling consortium claims the state is to blame for the delay because it had installed the steel casing that Bertha hit. The state claims the location of the casing was disclosed to the contractor before the tunneling began.