Unless you have been living in a tunnel (in which case you probably wouldn’t be reading this) you have no doubt heard about the problems facing the SR 99 tunnel in Seattle.
To recap, the project is being delayed due to issues with seals on the TBM’s main bearing. The machine was initially stopped on Dec. 6 and STP spent much of December reducing water pressure in the ground around the machine in order to inspect the excavation chamber and look for objects that might be blocking the machine’s path.
On Jan. 2, contractor crews successfully reduced water pressure enough to visually inspect a portion of the excavation chamber. A piece of an 8-in. diameter steel pipe could be seen protruding through an opening in the machine’s cutterhead. The steel pipe is a well casing installed in 2002 following the 2001 Nisqually earthquake to help geologists characterize groundwater behavior in the area.
Following completion of inspections, crews re-started the machine on Jan. 28, pushing 2 ft to complete the tunnel ring that was in progress on Dec. 6. At that time, high temperature readings were encountered again, and the machine was shut down again for further evaluation. On Feb. 7, it was reported that damage to the seals protecting the main bearing were discovered.
On March 13, STP submitted its preliminary plan for accessing the machine to make repairs. The design for a circular access pit was under review by the Washington State Department of Transportation (WSDOT) at presstime. The 120-ft-deep pit would be constructed in the closed portion of Alaskan Way South between South Jackson and South Main streets.
According to a report by an expert review panel released Feb. 27, WSDOT still expects the Alaskan Way Viaduct Replacement Program to be successfully completed within current budget, although likely with a delay in the schedule.
The interesting part of this is the attention that the SR 99 project is receiving in the mainstream media. TV, radio, print, social media – all have been captivated by this project, even before the trouble started. It became really apparent how big of story this was when friends and family started asking me about the status of the project. I hadn’t fielded questions like that since the Big Dig was in the headlines.
The funny thing is, it’s not just the world recording-setting project in Seattle that is garnering attention. It seems like every other day that I see on tunnel-related link about projects in Washington, D.C., San Francisco, New York, Los Angeles. (Does every TBM have a Twitter handle now?) Here in Northeast Ohio, there is plenty of local coverage about the NEORSD’s Euclid Creek Tunnel and Lorain’s Black River Tunnel. Recently, there was a series of reports about green infrastructure and its viability in combating CSOs vs. tunneling.
The good news is that news coverage increases the visibility and viability of tunneling projects, especially so when they are completed without hiccups. The downside is some owners have been extremely cautious about discussing their plans, perhaps fearful that revisions to the plan may indicate incompetence or wastefulness with resources – so mum is the word.
For the most part it seems that public outreach and information by agencies has increased. Many projects have dedicated websites and community meetings are a must. The attention to tunneling projects is here to stay, another challenge and opportunity for the industry as it continues to evolve.