AASHTO Journal, 20 December 2013
Washington State Department of Transportation officials announced last week it had stopped Bertha, the world’s largest tunneling machine, which is digging the SR 99 tunnel in Seattle, part of the project to replace the Alaskan Way Viaduct. WSDOT and its contractor, Seattle Tunnel Partners (STP), reported something was blocking Bertha, so crews are now working to determine what that blockage is and how to proceed.
“We’re confident STP has the right people and the right approach in place to safely determine what’s causing the obstruction,” said Matt Preedy, deputy administrator for the Alaskan Way Viaduct Replacement Program, in a statement. “Once they know what the obstruction is, our contractor will be able to select the best path forward.”
News on Bertha’s halt has been reported in many media outlets, though the most updates have come from Bertha’s own Twitter account.
“Seeing some reports that I’m stuck. I’m working fine, but have encountered an obstruction. I’ll keep you posted,” Bertha tweeted on Dec. 9. On Wednesday, she updated the public on what crews were doing to find that obstruction. “We’ve installed 6 out of 10 wells and pumped 300,000 gallons of water out of the ground near my face. Inspections could start Friday or Saturday.”
Those wells lower the water pressure in the ground, allowing workers to safety enter the excavation chamber in front of the machine to see what the obstruction might be.
The SR 99 tunnel project is expected to cost more than $2 billion, with funding coming from several sources including federal, state, and local partners, money from tolls, and gas tax funds. WSDOT said the tunnel should be open to drivers in late 2015, though it is not clear at this time if this delay will affect that schedule.
Additional information on the SR 99 Tunnel Project is available here.