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WSDOT Statement on SR 99 Tunneling Machine

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Date:  Tuesday, December 10, 2013

Contact: KaDeena Yerkan, Alaskan Way Viaduct Replacement Program communications, 206-805-2846, 206-795-1876 (mobile)

Statement by Program Administrator Todd Trepanier:

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.

Tunneling is challenging work. This section of the tunnel drive is very difficult due to the location of the machine and the nature of the historic fill soils in the area. Seattle Tunnel Partners has completed more than 1,000 feet of the 1.7 mile tunnel. WSDOT and Seattle Tunnel Partners have taken a number of precautions to minimize risk along the route, but have understood that challenges would be encountered along the way.

Additional information will be available on Friday.

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