GeekWire » The Washington State Department of Transportation (WSDOT) takes viewers on a behind the scenes construction tour of the new double-deck State Route 99 tunnel. WSDOT’s Deputy Administrator explains how the tunnel boring machine, known as Bertha, works to dig through the ground and place concrete rings to form the tunnel wall as she goes. Watch as the tunnel takes shape and construction crews build the framework and pour concrete for the roadway. It is estimated the new tunnel will use enough concrete to fill nine football stadiums. Click here for the video.