Seattle Tunnel Partners progress update: Construction of the access pit’s underground walls wraps up, preparation for dewatering begins

Posted on Aug 28 2014 12:24 PM

As we head into the last long weekend of the summer, we thought it was time for an update on Seattle Tunnel Partners’ progress to build the circular pit (pdf 2.5 Mb) that crews will use to access and repair the SR 99 tunneling machine. 

The last time we updated you, STP announced that crews would continue to install the underground walls of the access pit through August. STP has notified WSDOT that there is one pile left to install before the circular pit is completed; they expect to finish it by the end of the week. Additional piles will be installed near the pit as part of the support system for the modular lift tower - the large crane that will hoist the machine’s 2,000-ton cutterhead and drive unit out of the ground.

Next up, dewatering wells. STP has notified us that crews will install several dewatering wells both inside the access pit and inside the enclosed area south of the access pit around the tunneling machine. Prep work is beginning now and crews should have them installed by mid-September. These wells will lower the groundwater inside the enclosed areas to make it easier to move the tunneling machine into the access pit, as well as to excavate the pit.

STP has notified us that tunneling machine operators will start Bertha in order to check internal systems in preparation for mining into the circular pit. Also, pieces of the three cranes that will be used to lift tunneling machine pieces out of the access pit are continuing to arrive from around the world. Soon you will see these pieces being assembled next to the access pit.

STP still expects to resume tunneling in March 2015. For a better view of construction, check out our time-lapse camera, or view photos of recent construction on Flickr.

Additional resources


Previous updates 

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

April 29, 2014 update - A summary of change orders on the SR 99 Tunnel Project

April 21, 2014 update - SR 99 tunneling machine to resume digging in March 2015

Click here to see a full archive of progress updates