Oct. 14 project update: Preparing Bertha’s future path

Posted on Oct 14 2015 12:57 PM
This week, Seattle Tunnel Partners will begin treating the ground just north of the access pit. This work – known as jet grouting – will inject a mixture of cement and water into the soil, which will stabilize the ground above the tunnel as the machine exits the access pit. 
STP started setting up equipment for this work earlier this week. When the operation begins, crews will use a high-pressure pump to inject grout into the ground adjacent to the access pit’s north wall, creating a set of interlocking columns approximately five feet in diameter. The top of the columns will begin approximately 20 feet below the surface, and will extend down approximately 40 feet, stopping just above the tunnel route. STP expects this work to take approximately six weeks.
Meanwhile, STP and manufacturer Hitachi Zosen are continuing to reconnect machine parts in preparation for mining. That work includes welding pieces together, and reconnecting hoses and wires. STP Project Manager Chris Dixon outlines the steps STP is taking to resume tunneling in this video (links to YouTube). 
You can follow @BerthaDigsSR99 on Twitter for updates. We’ll also continue to post photos and videos as work progresses. 

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