WSDOT announced on Valentine’s Day that the plan to repair the damaged Bertha TBM was not ready yet, as engineers from Hitachi Zosen, the machine’s manufacturer, would need until the end of the month to have the plan ready. They did say maintenance would need to be done in front of the face, requiring the construction of a vertical shaft. It sounds like more work for STP JV team member Malcolm Drilling, and they may already have started on it. We’ll keep you posted. [Source: WSDOT. Image: Seattle Times]
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The Seattle Times (hat tip to ASCE SmartBrief) has reported that seven voids have been discovered above the Beacon Hill Tunnel with one opening up at the ground surface. The tunnel is being constructed by Sound Transit, the area’s transportation agency as part of a roughly $2.6 billion (yep, billion) light-rail project connecting downtown Seattle with the University of Washington and SEA-TAC airport. The voids were a result of running sand pockets in the otherwise stable clay units that were encountered by the tunnel boring machine or TBM. These voids migrated up like a chimney with one reaching the surface, almost 160-ft above the tunnel. This void was apparently 21-ft deep and opened up in a resident’s front yard and could have easily swallowed her up as she noticed it while gardening. The other voids were discovered at a depth of 20- to 65-ft below the ground surface. More after the break. (Illustration from Seattle Times)