Seattle Tunnel Partners has reported it has now bored more than one-half mile of the SR 99 tunnel on Seattle’s Alaskan Way Viaduct Replacement Program. As of June 13, Bertha, the 57.5ft diameter Hitachi Zosen EPBM SR 99 tunneling machine, had traveled a total of 2,724 feet and installed 411 concrete rings.Crews have tunneled more than 1,100 feet since leaving the machine’s most recent planned maintenance stop near Yesler Way on April 29. The completed bored tunnel will be 9,270 feet.
The top of the machine’s cutterhead is approximately 115 feet below Madison Street, east of Western Avenue. It’s approaching the southern edge of Zone 4, which continues the tunnel’s path toward First Avenue.
STP has begun preparing for its next planned maintenance stop. The details of the stop are still being developed, but it will likely occur sometime in July. During the stop, STP crews will inspect the machine and perform cutterhead maintenance, a process that could take several weeks.