Approximately 20 percent of the SR 99 tunnel was designed to be built without Bertha, the SR 99 tunneling machine. Seattle Tunnel Partners bored more than 1,000 feet of tunnel before they stopped to repair Bertha. Since then, they have built an additional 1,200 feet of tunnel using cut-and-cover tunnel construction. This video gives a close-up look inside the newest part of the project to learn more about the tunnel built without Bertha.
–wsdot on YouTube