SEATTLE — Now that the Bertha access pit has been excavated, officials say the next step in reaching the SR 99 tunneling machine is to dig through the concrete wall at the bottom of the pit.
WSDOT tweeted a photo of the 120-foot deep access pit which crews finished excavating on January 30th.
Alaskan Way Viaduct Replacement Program administrator Todd Trepanier says Seattle Tunnel Partners have been building a concrete cradle at the bottom of the pit. This will support the machine after it moves through the pit’s 20-foot thick southern wall.
“The next step is to tunnel through the concrete wall, per STP’s plans. The length of time it takes Bertha to reach the pit will depend largely on her ability to mine through and digest the concrete. If she’s unable to mine through the wall, STP will create an opening from within the pit to give her an unobstructed path forward. Once inside the pit, crews will prepare the machine for disassembly and use the massive red gantry crane to hoist the front end of the machine to the surface for repairs.”
For months the world’s largest tunnel-boring machine has been damaged and sitting idle underneath Seattle. Setbacks have plagued the multibillion-dollar project.
Once contractors reach Bertha, they will replace the machine’s damaged cutter head and try to get it digging again.