TBM Bertha unstuck and on its way

Last Tuesday in Seattle, the world’s largest TBM started moving again after nearly eight weeks of standing still some 60 feet underground. A 119ft long steel pipe was found to be the mystery object that had forced Bertha to stop on December 6, but WSDOT says it needs some time to define the specifics of the incident. WSDOT announced a two feet progress of the Tunnel Boring Machine and that maintenance work is to be made after its first move where it is required.

This step forward is enough for workers to fasten the next concrete ring at the rear of the machine, while the TBM is moving on, using hydraulic thrusters. According to Matt Preedy, deputy project administrator for the state Department of Transportation (DOT), after 10 days of inspection no significant obstacles were found inside the cutter-head of the machine or the surrounded soil and no mechanical problem was detected. Although Todd Trepanier, the DOT’s Highway 99 administrator believes that the machine might need to be modified due to the saturated soil and the groundwater flow, Preedy argues against. At the same time, Seattle citizens are worried about the cost as well as the project’s progress. According to records obtained by the Seattle Times, half of the project’s budget has been spent and Bertha has completed almost only 10 percent of its total path.

Sources: G13FOX News, The Seattle Times