Contractor Seattle Tunnel Partners (STP) has begun installing the SR 99 tunnelling machine’s redesigned seal system.
The tunnel boring machine (TBM), called Bertha, stalled in December 2013, delaying progress on the Alaskan Way Viaduct replacement project.
The new outer seal ring has been lowered into place, marking the first new piece to be installed in the machine as part of STP’s effort to resume tunnelling.
The new outer seal system arrived in October and was stored on-site prior to installation. The new inner seal system arrived last month and is currently being installed.