Dec. 22 project update

Posted on Dec 22 2014 1:38 PM

As crews wrap up work ahead of a brief holiday break, we wanted to provide updates on a few topics that have been of interest to the public in recent days.

Ground settlement levels remain stable

We are pleased to report that settlement levels near the SR 99 tunnel access pit have remained stable since Nov. 24. Seattle Tunnel Partners continues work on the pit with the dewatering wells on while our survey crews analyze data, and inspect nearby buildings and infrastructure. While some ground settlement was predicted due to dewatering, the settlement measured is greater and farther reaching than anticipated. Engineers are still evaluating whether other factors are involved that could explain the discrepancy. We will continue to conduct daily inspections of the viaduct and watch the survey data closely as STP moves forward with their work.

Three survey teams are collecting and analyzing data: WSDOT, STP and the City of Seattle. These teams have determined that some of the survey control point readings were not accurate and need to be corrected. We anticipate the adjustment will decrease the previously reported amount of settlement. Concurrence by all teams, as well as updated survey materials, is anticipated in early January.

We have conducted 50 building surveys since Dec. 7, and our survey efforts are ongoing. Survey crews have found some minor cosmetic damage in a handful of buildings, but no structural damage has been discovered.

Access pit construction

Excavation at the access pit resumed on Dec. 16, following a brief stoppage. The pit, which will be 120 feet deep upon completion, is now 90 feet deep.

STP has taken a break from excavation to remove five piles from inside the pit. These 3-foot diameter piles do not provide structural support. They were installed as plugs to hold grout in place. To access these grouted areas and complete the grouting process, STP must now remove these plugs, as shown in the drawing below.

Removing the piles and adding more grout will take approximately two weeks. After this work is done, excavation of the access pit can resume.

Updates on the long-term schedule

We continue to receive questions about the long-term schedule for this repair effort and the tunnel project in general. Back in June, STP’s newly released repair plan showed that tunneling would resume in March. We knew the work would be difficult and there was a risk it would take longer than predicted.

Each month, STP provides WSDOT with an updated schedule. This schedule includes all of the extra work days STP believes they are entitled to as a result of the tunneling stoppage and other delays. The schedule submitted for October, for example, now shows that tunneling will resume in late April 2015, and the project will be open to traffic in August 2017 – long after the original December 2015 open to traffic date and also later than the November 2016 date STP has been targeting since the tunneling stoppage.

While STP provides us with a schedule each month, we cannot endorse a project completion date until the work is further along. This is very difficult work and certain construction activities have and will continue to take longer than anticipated. While we are confident the project will be completed, a schedule we can endorse will likely come into greater focus only after the access pit is complete and the tunneling machine has demonstrated it can successfully mine.

As we’ve said before, any disagreements over who is responsible for delays will be dealt with in accordance with the design-build tunnel contract. It’s an issue that is of great importance to both WSDOT and STP, and we will address it in due course. In the meantime, we’re not letting it get in the way of the important work that needs to be completed.