The TBM has moved forward in her access pit wall this week, digging the 2m needed to build 161st concrete ring of the tunnel to replace the Alaskan Way Viaduct in Seattle in the US state of Washington.
Major repairs had to be carried out after the machine broke down more than two years ago while building the tunnel (link opens in new tab),
Contractor Seattle Tunnel Partners (STP) is preparing to mine through the approximately 5m-thick concrete wall in the coming days. Once beyond the wall, crews will begin tunnelling through native soils that will serve as the next stage of STP’s testing process. This section of the tunnel route includes an underground wall that was built to protect the Alaskan Way Viaduct while crews continue to test the machine.
With excavation under way again, STP is resuming its operation for removing excavated material from the tunnel. This is done via a conveyor belt that extends from the tunnel to the edge of the Port of Seattle’s Terminal 46. Material that contains concrete from the access pit wall will be hauled away by truck. Clean material – which crews will encounter once outside the access pit – will be taken by barge across Puget Sound to a reclamation site where it will be used to fill an old quarry.
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