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SR 99 update: TBM testing underway

Testing has started on the SR 99 tunnel boring machine’s (TBM) components in preparation for tunnelling to resume on the Alaskan Way Viaduct replacement project.

The tests have so far included the 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 contractor Seattle Tunnel Partners (STP) and TBM manufacturer Hitachi Zosen, 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 be undertaken later this month.

In addition, 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.

Tunnelling is expected to resume on 23 December 2015.

Project progress

While the TBM testing is underway, STP crews have finished treating the ground north of the access pit.

In order to stabilise the area where the TBM will exit the pit, grout has been injected into the soil.

A thin layer of sand will be placed at the bottom of the pit, and the rest of the pit will be filled after initial testing is complete.

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