When Seattle's Alaskan Way Viaduct was built in the 1950s, we didn't know much about earthquakes. California's Loma Prieta quake in 1989 opened our eyes when their viaduct collapsed and crushed 41 people.
And when the Nisqually quake in 2001 damaged our own viaduct, it sealed the deal for officials: The viaduct had to go.
To replace it, we brought in the world's biggest tunnel boring machine, Bertha. A project that was supposed to take 14 months took more than three times as long.
Reporter Carolyn Adolph gives us a primer on how the tunnel finally got through.
Editor’s note: What caused the Bertha breakdown is still an unsettled legal matter between the contractor and WSDOT. WSDOT disputes Seattle Tunnel Partner’s claim that the pipe caused Bertha’s damage.