Seattle Tunnel Partners has now installed all 84 underground piles associated with their plan for accessing and repairing Bertha, the SR 99 tunneling machine. Last week, crews installed the final of 11 piles that will support the modular lift tower – the large crane that will hoist pieces of the tunneling machine to the surface from a pit that’s currently under construction in the ground in front of Bertha. The piles that make up the underground walls of the circular pit were completed in late August.
Now that pile work is complete, crews are injecting grout into the ground to fill in gaps between the piles, and installing additional underground monitoring equipment in preparation for the next phase of construction. Crews are nearly ready to drill wells that will lower groundwater in enclosed areas near the machine. This will make it easier to excavate the access pit and move the tunneling machine into the pit later this fall. Drilling of these wells will begin later this week, and crews expect to complete well installation by mid-September so excavation of the pit can begin.
Bertha’s manufacturer, Hitachi Zosen Corp., has begun performing necessary inspections and tests as they prepare to tunnel into the access pit. As part of those tests, the tunneling machine recently mined forward approximately three feet. In addition to giving crews an opportunity to evaluate various systems within the machine, this small move forward positioned Bertha against the exterior wall of the access pit.
STP still expects to resume tunneling in March 2015. For a better view of construction, check out our time-lapse cameras, which include a new view of the pit as of Monday. You can also view photos of recent construction on Flickr.
- NEW Video: View an animation of repairs narrated by STP Project Manager Chris Dixon (view on YouTube or download WMV file)
- Seattle Tunnel Partners repair work plan (pdf 4.8 Mb)
- Graphics showing access pit construction (pdf 2.5 Mb)
- Time-lapse camera of repairs
- Video of crews building the access pit (view on YouTube or download WMV file)
- Video of crews reconfiguring the tunnel launch pit (view on YouTube of download WMV file)
- Brochure of STP's repair plan (pdf 1 Mb)