SR 99 Tunnel Update: TBM Testing Underway

SR 99 Tunnel Update: TBM Testing Underway

The SR 99 tunneling machine’s front end is in position to be reconnected to the rest of the machine in this Aug. 26, 2015, photo. TBM testing has begun with mining anticipated to resume in late December. (Photo from the Washington State Department of Transportation.)

Seattle Tunnel Partners (STP) and manufacturer Hitachi Zosen have begun testing components of the SR 99 tunneling machine as they prepare to resume mining, according to the project owner, Washington State Department of Transportation (WSDOT). A few initial tests were performed the week of Nov. 2, and several others are slated to occur in the coming weeks.

Highlights include tests of various pumps inside the machine, as well as the screw conveyor system that carries excavated material from the cutterhead to the back of the machine and out of the tunnel. All of the tests are being conducted by STP and Hitachi, who are jointly responsible for ensuring the machine is ready to complete the remainder of the tunnel drive. Future tests will include rotation of the machine’s cutterhead, which, according to STP, will occur in late November.

Some reassembly work is ongoing. Major components of the machine are in place, but crews continue to weld pieces together and reconnect wires and hoses. STP’s most recent schedule shows that the machine will be ready to resume mining on Dec. 23. This narrated video ( explains STP’s repair effort in more detail.

Elsewhere on the project, STP crews have finished treating the ground north of the access pit. They began injecting grout into the soil there last month to stabilize the area where the machine will exit the access pit. Crews will soon place a thin layer of sand at the bottom of the pit; the rest of the pit will be filled after initial testing is complete.

STP crews are also preparing to install glass walls at the operations buildings located at each portal. The north building’s glass will be installed first.

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