Seattle Tunnel Partners has released a conceptual plan showing what the excavation of the pit will look like to repair the damaged Bertha Tunnel Boring Machine. See below.
A pit 120 feet deep and 83 feet in diameter will be excavated so that the TBM can be driven into the pit and the cutterhead removed. Crews will then repair the seal system around the main bearing. [Source: WSDOT, Image Credit: Seattle Tunnel Partners and Brierly Associates by way of WSDOT]