Seattle Tunnel Partners resumed mining late Monday following 10 days of hyperbaric maintenance on Bertha, the SR 99 tunnelling machine. 

Crews replaced approximately 300 of the nearly 500 scrapers on Bertha’s cutterhead during the hyperbaric maintenance period. As this post explains in more detail, the scrapers line the sides of the cutterhead spokes. STP also conducted other important inspections and maintenance during this time. 

Completing routine maintenance is an important part of ensuring that the machine continues to operate properly. STP will continue to perform inspections and maintenance as needed over the remainder of the tunnel drive. 

Crews are less than 2,500 feet from the receiving pit near Seattle Center where Bertha will emerge at the end of tunnelling. The top of the cutterhead is located approximately 160 feet below Third Avenue in Belltown.  

Progress updates are posted on Mondays and Thursdays at our Follow Bertha page. You can also follow Bertha on Twitter @BerthaDigsSR99. So for further information and progress please visit http://www.wsdot.wa.gov/projects/viaduct. Also click here and us/69 for the tunnelbuilder archive. 03/17