SEATTLE – On Saturday, Dec. 7, Seattle Tunnel Partners, WSDOT’s design-build tunnel contractor, proactively stopped tunneling. It was stopped after unanticipated and increasing resistance was experienced, possibly due to an obstruction, which significantly decreased the advancement rate of the machine and the volume of tunnel muck on the machine’s conveyor belt.
Seattle Tunnel Partners is currently evaluating various strategies to determine what is slowing the machine’s progress. The contractor is considering the shallow depth of the tunnel boring machine, the high groundwater table and the challenging nature of the historic fill soils at this location as they assess the strategies. Together, WSDOT and Seattle Tunnel Partners are taking the necessary steps to ensure that the chosen strategy can be implemented safely.