State Transportation Secretary Lynn Peterson says the agency “has had concerns” about how contractors have been operating tunnel-boring machine Bertha since July 30, when drilling began.
The admission came via an email Wednesday to state lawmakers, while the world’s largest drill spends its sixth week stranded in the soil near Pioneer Square.
Meanwhile, Seattle Tunnel Partners (STP) planned to send teams of five or six workers to the buried cutting face for the next couple of days to search for any objects that might be blocking Bertha or any damage to the front of the machine.
But the state Department of Transportation questions whether STP has been using the right strategies during this tricky, initial stage of the Highway 99 tunnel project.
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Peterson’s message says, in part:
“WSDOT has had concerns about the machine’s operations and critical systems since its launch on July 30, 2013. We have discussed these concerns with STP frequently over the past five months and this week sent a formal letter stating our concerns and asking STP how they will address them prior to tunneling under the viaduct and downtown. We are providing you [elected officials] with this information in lieu of a copy of the letter because it could be the subject of a potential future litigation between WSDOT and the contractor.”
On Monday, she requested several pieces of information, including a strategy from STP to regain lost time.
Peterson also sought an explanation as to why Bertha’s operators ran the machine at unusually high temperatures before shutting it down Dec. 6, when the rotary cutter stopped grabbing soil.
The tunnel drill had struck an 8-inch-diameter pipe Dec. 3, but contractors kept drilling for three more days — and in fact progressed 58 feet in a day, its best-ever pace.
Bertha is 60 feet deep, near South Main Street.
Solutions are critical right now, before the machine dives under the old Alaskan Way Viaduct and passes historic brick buildings in Pioneer Square.
Excess vibrations could damage the elevated highway, while mistakes in the soil-excavation rate could cause downtown buildings to sink.
Chris Dixon, project director for STP, didn’t comment Wednesday on Peterson’s message.
But earlier Wednesday, he said the contractors think something in the soil, as opposed to mechanical trouble, is to blame for the stall. The conveyor screw, for instance, is moving muck just fine, he said.
The $80 million drill, made by Hitachi, is still in a break-in period before the sale to STP is final, once Bertha completes 1,250 feet of mining.
At a news conference Wednesday just before Peterson’s email went to lawmakers, Todd Trepanier, WSDOT’s program manager, said, “We’re confident in STP’s ability to move this project forward.”
Trepanier later calledPeterson’s letter a form of due diligence that any strong owner would exert over such a huge project.
He said he believes the machine itself is free of problems and is up to the task of reaching South Lake Union.
In recent weeks, the state has portrayed the steel pipe as only a partial reason for the stoppage.
As for WSDOT’s concerns in earlier weeks, fiberglass became stuck in the conveyor screw, and “there have been cutting tools that have shown damage; there have been issues with heat, and there have been issues with muck flowing,” Trepanier said.
Peterson wrote Wednesday that WSDOT plans to call on tunnel experts for suggestions.
However, she warned lawmakers that she can’t “direct how STP does their work” or else the state will bear increased risks and responsibility, under the $1.44 billion contract.
STP provided some information to WSDOT on Tuesday
and planned to forward more details Wednesday night, Trepanier said.
The drilling from Sodo to South Lake Union has been delayed by extra testing last winter in Japan, by a labor dispute in August — and since Dec. 6 by a blockage that officials say they don’t yet know how to resolve.
Meanwhile, Dixon said 20 workers on his team have been trained to inspect the cutting head, under about 1½ times atmospheric pressure, after compressed air is pumped in.
Workers will use flashlights and cleaning tools to get a look around the 57-foot diameter rotary cutter — after four deep, vertical shafts failed to hit a big object, and a worker who was lowered down a shaft didn’t find an obstruction.
High pressure exists here because groundwater permeates the soil.
Pressures around the cutter were forecast at perhaps double the surface pressure, but STP will significantly reduce pressure — and improve worker safety — by using 10 temporary wells to pump away groundwater.
Worldwide, builders have conducted “hyperbaric interventions” in tougher conditions beneath the Elbe River in Hamburg, Germany, under the Yangtze River in Nanjing, China, and at the Brightwater sewer tunnel north of Seattle, and elsewhere.
More days or weeks could be needed to fix any problems and resume digging. It’s entirely possible Bertha might need to be modified, said Trepanier.
Big tunnel projects usually run into “some unique issue,” he said, but the job nearly always gets done.
Mike Lindblom: 206-515-5631 or email@example.com. On Twitter @mikelindblom