Dec. 16 project update
Posted on Dec 16 2014 12:17 PM
On Tuesday, Dec. 16, we informed Seattle Tunnel Partners that crews will be allowed to resume excavation at the SR 99 tunnel access pit. STP expects to resume digging this evening.
On Dec. 5, we shared information with the public that approximately one inch of settlement had occurred near the access pit. While we have not yet confirmed that STP’s dewatering efforts are the only contributing factor to this settlement, we are confident that excavation is not a factor. Public safety is our top priority as our contractor moves forward with their work.
Excavation was stopped at WSDOT’s direction on Dec. 12. While no significant ground settlement had been observed since Dec. 5, we suspended excavation to give our team time to gather more survey data and review STP’s contingency plan for turning off the dewatering wells, should that become necessary. We have now reviewed STP’s plan and gathered additional data from the weekend that shows the recently measured settlement has stabilized.
We will continue to conduct frequent surveys and analysis, including determining the cause of the observed settlement, and provide updates to the public.