How far will Bertha tunnel beneath the viaduct each day?

Tags: 99closure, 99safety

Mining rates will vary throughout the #99closure. The contractor Seattle Tunnel Partners expects to start slowly as crews mine out of the block of concrete near Yesler Way in which the tunneling machine has been stopped for its planned maintenance. The machine must dig through approximately 10 feet of concrete to exit the maintenance stop and enter the soil near the intersection of Yesler and Alaskan Way. Crews intend to proceed deliberately throughout the first weekend and then pick up speed further into the closure. While STP will be working 24/7 during the closure, the machine will not be tunneling constantly. Crews will have to stop tunneling to build tunnel rings and do machine maintenance.