Testing starts on Big Bertha1 December 2015
USA – Commissioning of the SR 99 TBM continues as Seattle Tunnel Partners prepares to resume mining. STP began testing machine components earlier this month as crews continued welding pieces and reconnecting hoses and cables.
The Washington State Department of Transportation made the announcement on November 24, which marked the first sustained rotation of the cutterhead since the machine broke through the southern wall of the access pit on February 19. STP indicated they will rotate the cutterhead in both directions for about one hour at a time. The contractor had begun rotating the machine's cutterhead a few degrees at a time the week prior, stopping periodically to take measurements before completing a full rotation.
During the next phase of commissioning, STP will backfill the access pit with sand and gravel to prepare the machine for mining. STP's most recent schedule shows that the machine will be ready to resume mining on December 23. The state cannot verify the contractor's schedule.