Seattle Light-Rail Tunnel Likely to Break Ground This Year

Excavation for the $700M Lake Mead Intake No. 3 Project was put on hold after tunneling encountered a fault carrying groundwater that flooded the excavation and submerged equipment. The flooding occurred over about 4-days, so […]

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)

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Terracon posted a new blog post about a unique hybrid soil nail and anchored soldier pile wall excavation support system for the Tower 12 Building project in Downtown Seattle.  The project involves a 60-foot deep […]