July 11 project update: New video shows that changing Bertha's cutting tools is no easy task

Posted on Jul 11 2016 4:39 PM
Seattle Tunnel Partners crews are making good progress as they continue performing routine maintenance on Bertha, the SR 99 tunneling machine.
 
The machine has been stopped approximately 120 feet below Spring Street, just west of First Avenue, since June 23. There, crews have been checking and maintaining equipment, and are on schedule to resume mining by the end of the month. 
 
Much of their focus is on inspecting and, when needed, replacing the cutting tools that scrape away the earth in front of the machine. This work must be completed in hyperbaric conditions similar to those found in an underwater dive (this post explains hyperbaric work in greater detail).
 
These conditions require workers to adjust their bodies to greater air pressure than we live and breathe in every day. Crews are only able to spend approximately one hour working in this increased air pressure. As a result, five crews of seven people take turns replacing the tools and performing other work in the space behind the cutterhead.   
 
Bertha’s cutterhead is outfitted with more than 700 tools. So far, STP has replaced only 25 of the more than 400 tools they’ve inspected during this maintenance stop. 
 
New video captured by STP shows that performing maintenance on the cutterhead is no easy task. In addition to working in hyperbaric conditions, crews must complete their work in a confined space. The cutting tools shown in the video weigh approximately 75 pounds.
 
 
We’ll continue to provide additional updates as STP’s work progresses.
 
Recent tunneling updates 
June 28 project update: New videos show crews at work inside the SR 99 tunneling machine
June 23 project update: Tunnel crews arrive at planned maintenance stop
June 20 project update: Tunnel crews nearing planned maintenance stop
June 13 project update: Bertha passes the half-mile mark
May 31 project update: Tunnel boring now 25 percent complete
May 26 project update: Bertha reaches Western Avenue

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