Bertha's cutter head is lifted into place, during the machine's assembly in 2012. Credit: WSDOT
Fixing Bertha’s main bearing seal will take months, Washington State Department of Transportation said Monday night.
To repair the seal, Seattle Tunnel Partners, the contractor digging the Highway 99 tunnel, will have two options. One is to dig a shaft in front of the idled boring machine, which sits 60-feet beneath the ground in Pioneer Square, amid groundwater-inundated earth and muck. The other is to access the bearing through the back of the tunneling rig. The company, WSDOT said, will make a choice about the best way to undertake the repairs by the end of this week.
“[Seattle Tunnel Partners] has not yet fully determined the cause of the seal problems,” WSDOT said late Monday night in a press release.
The nearly $90 million machine has moved a little more than four feet since Dec. 7, after it encountered unusual resistance while digging. The damaged seal protects Bertha’s main bearing, which allows the machine’s 57.5-foot “cutter-head” to spin. After moving the machine a short distance during the last week of January, sensors showed unusually high operating temperatures. The hotter than normal readings led workers to find the busted seal. WSDOT has not indicated whether any other part of the machine’s $5.1 million main bearing assembly is damaged.
As for who will pay to fix the machine, Seattle Tunnel Partners, WSDOT said, has “not shown any evidence that suggests the state or taxpayers will be responsible for cost overruns associated with these repairs.” The contractor was not available for comment when WSDOT announced the extent of the delays.
For now, WSDOT said, the stalled machine will not cause delays with the Elliott Bay Seawall replacement project, which is underway nearby. The Seattle Department of Transportation is heading up that project. Old age and wood-boring sea creatures called "gribbles" have left the seawall vulnerable to severe damage or failure in the event of a strong earthquake.
Mayor Ed Murray announced on Monday that he’d formed a new Office of the Waterfront, responsible for planning and managing city projects and partnerships in the area. He addressed the seawall’s relationship to the tunnel in an emailed statement.
“The Seawall needs to be replaced because it isn’t safe,” Murray said. “This public safety issue doesn’t disappear while the Seattle Tunnel Partners and WSDOT work to get Bertha moving again.”
The bearing seal wasn’t the only problem Seattle Tunnel Partners found in recent weeks. Investigations that followed the early December shutdown revealed that the spokes on the machine’s cutter head were jammed with soil. WSDOT Program Administrator Todd Trepanier said last week that a variety of factors, including soil type, additives injected into the mined soil and the machine’s speed, could’ve caused the clog.
The deep bore tunnel is the centerpiece of the estimated $3.1 billion Alaskan Way Viaduct replacement project. Bertha is scheduled to finish digging the 1.7-mile underground roadway, which runs from Sodo to South Lake Union, in late 2014. A four-lane highway inside the tunnel is slated to open by the end of 2015. So far the machine has completed about 1,000 feet of mining and is stopped near South Main Street. WSDOT said it is waiting for Seattle Tunnel Partners to provide a plan that details how they can "recover lost time." A January Crosscut analysis raised questions about whether the drilling can be done in time.
Based on the contract terms, Hitachi Zosen, the company that manufactured the machine, owns it for the first 1,300 feet of digging. After that point, Seattle Tunnel Partners, a partnership between Dragados-USA and Tutor Perini, will take over ownership of the tunneling rig. Hitachi Zosen representatives are here, working with Seattle Tunnel Partners to diagnose and fix Bertha’s mechanical problems.