The LA Times is reporting that the California bullet train project may be facing significant budget and schedule issues, largely because of a 13.5-mile tunnel beneath Pacheco Pass east of Gilroy. The article reports that the current budget for the 54-mile segment between Gilroy and Chowchilla is $5.5B, but experts that they interviewed for the story put the cost of the twin-bore tunnel itself at between $5.6 to $14.4B. Geological and geotechnical drilling and testing are currently underway for the tunnel which will be up to 1,000 feet below ground through the challenging Franciscan Complex. Don’t forget about the challenges of a seismically active area and at least one major fault crossing. The designers and engineers for that project are going to have their hands full with that one!
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)