- Sydney Brownstone
- WSDOT deputy program administrator Matt Preedy explained some things about the ongoing downtown tunnel project last night.
The only thing that's left between Bertha, the tunnel boring machine that's been stuck for a year below Pioneer Square, and the sweet, sweet freedom of release is 20 feet of concrete. On Thursday night, Washington State Department of Transportation deputy program administrator Matt Preedy explained how, exactly, the contractor plans to get Bertha into the bottom of a newly finished, 120-foot-deep, concrete-lined pit where workers will then tug her* teeth and damaged front-end into the light.
Preedy told a room of 20 or so people assembled at Milepost 31, the small Pioneer Square museum dedicated to the tunnel project, that even in her damaged state Bertha should be able to roar back to life and "make it all the way through" the 20 feet of concrete lining the wall of the rescue pit. "The contractor is confident," Preedy said, "but they do have a contingency plan if she does not,"
Keep in mind, though, that Bertha is broken. And how broken? Her seal array, the part of the machine that separates the gunk in the cutterhead from the gears behind it, is "basically 100 percent damaged," Preedy said.
So what's that Plan B for getting Bertha past 20 feet of concrete if she can't chew through it? Preedy explained that the contractor would lower an excavator to the bottom of the pit, build a platform for it, and mount a "giant jackhammer" to the end.
"They would jackhammer out a Bertha-sized hole, and all the concrete would fall into the shaft, and you’d have to get all the concrete out, which would take time," Preedy told me. "But eventually they would be able to chip a hole back to the front space of the machine and push the machine out."
And how much time would the process of getting Bertha out take? Preedy wouldn't venture any kind of estimate.
Dewatering of the pit will continue while the machine is repaired and the pit refilled. Preedy said that the water is being extracted at a constant rate, and ground and groundwater levels remain stable.
*By the way, I know it's tradition to refer to large machines and vessels commandeered by primarily male crews as female, but can we please give Bertha another gender? The tunnel boring machine is maybe the most phallic object in the world. As my colleague Heidi Groover just said, "How far is this going to set feminism back when it fails?" Yeah. YEAH.