Seattle Tunneling Project Steadily Moving Forward.

The article reports on developments in the replacement of the Alaskan Way Viaduct with bored tunnel in Seattle by the Washington State Department of Transportation. Topics mentioned include the use of the Bertha tunnel-boring machine which puts tunneling on track to be completed in 2017, performance of the machine as the soil becomes dense and firm, and the decision of the construction team to stop and change precutting bits.