Areas surrounding the access pit being excavated to rescue the stalled Bertha TBM have experienced settlement as much as 1 to almost 1.5 inches according to a draft figure released by WSDOT on December 11, 2014. The aging and seismically deficient Viaduct itself has experienced 1 inch of settlement as well. Structural engineers have inspected it as well as numerous buildings in the area and have not found structural damage. The settlement is thought to be related to the dewatering associated with the access pit construction. The excavation was within 3 feet of the bottom when the settlement issues were first announced on December 5, and WSDOT has since allowed the contractor to complete the excavation. [Source: Read more information in the update provided by the WSDOT Alaskan Way Viaduct Replacement Project team. Image: WSDOT]
In keeping with our theme of rising costs on tunnel projects, the Brightwater sewage-treatment plant and treated waste pipeline project in King County Washington (Seattle area) is now up to at least $1.84 billion according to the lead consultant on the project. The treated waste pipeline is 13 to 14-miles long and at depths of 40 to 440-ft! It is being constructed nearly entirely by TBM. One source of delay was due to a tunneling subcontractor not being able to get parts (ball bearings?) because they were all being requisitioned by the US War Department for use in military equipment in Iraq and Afghanistan. Click through for information sources and links.