Bertha, the tunnel boring machine digging Seattle's new Alaskan Way Viaduct replacement tunnel, has nearly reached the tunnel's halfway point after digging 4,000 feet. The tunnel is now about 43% complete, and crews have already installed 607 concrete rings to form the tunnel walls.
[VIDEO] Drone Flies Through Seattle's SR 99 Tunnel Bertha is Digging
Bertha has to move through 10 zones that make up the entire project and is currently on the border between zones 5 and 6.