Access pit excavation is underway

Posted on Oct 20 2014 11:19 AM
Seattle Tunnel Partners has started digging the circular pit (pdf 2.5 Mb) crews will use to access and repair Bertha, the SR 99 tunneling machine. On Friday evening, Oct. 17, an excavator rolled into position to the west of the Alaskan Way Viaduct near Pier 48, where STP stopped tunneling last December after Bertha overheated. There, crews began taking the first scoops of soil from what will become a 120-foot-deep, 80-foot-wide pile-supported pit.
 
Approximately 20,000 cubic yards of soil will be removed from the pit over the course of excavation. Because a number of other important construction activities are competing for space near the pit, there will be many days when excavation doesn’t occur. Contaminated soil will be hauled by truck or barge to a disposal facility; STP will store non-contaminated soil and use it to fill in the pit after tunneling resumes. 
 
Meanwhile, crews are continuing to lower groundwater in enclosed areas near the machine and prepare for installation of the massive crane that will be used to hoist pieces of the machine to the surface for repair later this fall (simulated image below).
 
Access pit simulation
 
You can watch the pit take shape on our time-lapse cameras. Taken from our south-facing camera, the shot below shows you STP’s progress as of Monday morning, Oct. 20.
 
Access pit on October 20
 
Additional resources

 

Previous updates

Oct. 10, 2014 update – Seattle Tunnel Partners lowering groundwater near the access pit

Aug. 28, 2014 update – Construction of the access pit's underground walls wraps up, preparation for dewatering begins

July 28, 2014 update – Construction of the access pit's underground walls will continue through August

June 16, 2014 update – Contractor announces details of repair work plan for the SR 99 tunneling machine

May 8, 2014 update - With environmental review complete, access pit construction begins in earnest

Click here to see a full archive of progress updates