Explaining progress on TBM Bertha repairs 08 Oct 2015

Work continues at the bottom of the 120ft-deep access shaft where Seattle Tunnel Partners is readying Bertha, the SR99 tunneling machine, for the remainder of her 2.6km tunnel drive beneath downtown Seattle.

With repairs at the surface complete and all major components of the tunneling machine safely in the shaft, STP and TBM manufacturer Hitachi Zosen are focused on completing the reassembly portion of their repair effort.

Crews are currently welding pieces of the machine back together, and reconnecting hundreds of wires and hoses that are integral to the tunneling operation. Although significant work is ongoing, much of it is cannot be seen from the surface.

In the latest video from WSDOT, STP Project Manager Chris Dixon recaps the repair effort to date and explains what is next as they work to get Bertha moving again. The 17.6m diameter world record diameter machine has not made any progress since the failure of the main bearing seals in December 2013. Repairs have included a replacement sealing system, which is designed to be more robust and more accessible in the event of further problems during the tunnel drive; the fitting of a new main bearing; and general strengthening of the machine.