It looks like it’s bad news again for the in-progress Alaskan Way Viaduct replacement tunnel in Seattle, and for Bertha, the nickname for the world’s largest tunnel boring machine being used to create the underground highway. Bertha has been idle for much of 2014 due to a broken cutter system. And now the complex process to reach Bertha 60 feet below the surface has been halted. Recently a team of engineers discovered that the soil around Bertha is sinking as much as 1.4 inches in some places.
Rendering of new entrance to the Alaskan Way Viaduct (WSDOT)
The project will be further delayed as engineers get a better reading on the settling of the soil. Originally the viaduct was scheduled to open in December 2015, but now the date has been set to sometime in 2017.
Somewhat ominously, the Seattle Times reported: “The viaduct settlement this fall could mean that some portions of the structure have sunk more than 6 inches since the 2001 Nisqually earthquake—exceeding a safety limit that WSDOT publicized last decade.” Let’s hope the engineers and officials get to the bottom of this soon.