Construction of the underground walls of the recovery shaft that will be used to gain access to TBM Bertha's bearing seal assembly and main bearing is completed, following the sinking of the 84th and last pile.
Seattle Tunnel Partners (STP), the construction joint venture of Dragados/Tutor Perini, now moves into a dewatering phase by installing wells both inside and outside the 120ft deep x 80ft diameter access shaft, and also around the TBM. This will enable lowering of the groundwater to make it easier to excavate material from the shaft and make it easier for the TBM to drive into when the time comes.
STP confirms that TBM Bertha has advanced 3ft (just under 1m) underground, the first time she has moved since January, to allow machine manufacturer Hitachi Zosen to evaluate various systems to allow further inspections and tests. The small advance has also placed Bertha against the exterior wall of the circular recovery shaft, into which she is scheduled to drive into later in the year (2014). Pieces of the three cranes that will be used to lift the cutterhead and other parts of the TBM out of the shaft are continuing to arrive from around the world.