Dec. 23 project update: Bertha builds another ring
Posted on Dec 23 2015 2:07 PM
Seattle Tunnel Partners built the SR 99 tunnel’s 160th concrete ring on Tuesday before securing the worksite for the holidays. Crews pushed the tunneling machine slowly forward in the access pit over the course of the day, testing its performance as they mined the 6.5 feet needed to install the next ring. A video of the ring-build is below.
In all, Bertha has excavated 8 feet of tunnel since STP restarted the machine early Tuesday. STP crews – which have been working long hours in the weeks leading up to the machine’s restart – will take a break over the holidays before resuming tunneling in the first week of January.
When work resumes, crews will mine through the concrete wall of the access pit and into the native soils that will serve as the next stage of STP’s testing process. This section of the tunnel route – like the 1,091 feet that came before it – is protected by underground walls that were built to hold the ground in place while crews continue to test the machine.
Bertha will mine toward an underground block of concrete approximately 450 feet north of the access pit. This area is the third and final protected maintenance stop, or safe haven, that STP built prior to the start of tunneling. According the STP’s most recent schedule, the machine will spend up to one month at the safe haven while crews perform maintenance and make final adjustments before tunneling beneath the Alaskan Way Viaduct.
WSDOT will fully close SR 99 through downtown for approximately two weeks while the machine passes beneath the viaduct. STP’s latest projections show that the closure will occur in March, but the actual closure date will depend on Bertha’s progress and the state cannot verify the contractor's schedule. Check our #99closure page as the closure approaches for additional details.
Look for our next update in early 2016. Happy holidays from the Alaskan Way Viaduct Replacement Program.