Dec. 18 project update: Work continues at the access pit

Posted on Dec 18 2015 2:17 PM
Seattle Tunnel Partners has spent much of the week backfilling the SR 99 tunnel access pit. By Friday, only part of the machine’s shield and cutterhead were visible from our time-lapse camera. Crews stopped backfilling on Wednesday afternoon to repair a mixing arm that broke off inside the machine during testing of the cutterhead. Backfilling has since resumed and will continue over the weekend.
 
STP has indicated they may fill the remainder of the pit with a concrete-sand mixture in addition to material removed during excavation. Using the concrete-sand mixture – rather than sand and soil, as STP previously planned – could reduce the time it will take to complete backfilling. Additionally, the deep dewatering wells that have been used to control groundwater in the pit may be turned off sometime in January. STP previously planned to turn them off this month.
 
STP has told us they plan to move the SR 99 tunneling machine forward by Dec. 23, the date shown in their most recent schedule. As part of their testing program, STP intends to tunnel forward a short distance in the pit before taking a break for the holidays. After the holidays, STP plans to mine out of the access pit toward a planned maintenance stop approximately 450 feet to the north. Along the way crews will mine forward and install tunnel rings while continuing to run tests.
 
The state cannot verify the contractor's schedule, but we will continue to provide updates as STP's work progresses.
 
To learn more about STP's repair effort, watch this narrated video (links to YouTube).
 
STP backfills the access pit
Crews backfill the SR 99 tunnel access pit on Tuesday.
 
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