The INSANE Machine That Dug Under an Entire City

How can an 8,000-ton machine disappear beneath a city and build a tunnel as it moves? This is the story of Bertha, the enormous tunnel boring machine built for Seattle's SR 99 Tunnel — a machine over 300 feet long with a cutting head nearly 58 feet in diameter. Bertha was designed to excavate through Seattle's complex underground geology while managing groundwater pressure, removing enormous amounts of soil and installing the permanent concrete tunnel structure behind her. But just weeks into the project, Bertha stopped underground. What followed was a massive engineering rescue operation involving a huge recovery shaft, the removal of more than a thousand tons of machinery, a complete repair and a return underground. In this documentary, we explore how Bertha worked, why she failed, how engineers brought her back to life, and why the lessons from her failure continue to influence modern tunnel boring machines. The tunnel is what people see. The machine is what made it possible. Subscribe to Titan Grid for more extreme engineering, megaprojects and the machines building the future. #Engineering #TunnelBoringMachine #Bertha