Wednesday, December 17, 2014

The Saga of Seattle's Deep Bore Tunnel

In 2001 the Nisqually Earthquake hit Seattle.  Our house in West Seattle sustained some damage.  There was enough movement to slosh the water out of the upstairs toilet and send a couple of dressers to the floor.  The brick chimney did not fall down so we were very happy about that.
The worst part of the earthquake was the traffic.  The Alaskan Way Viaduct is a double decker elevated highway built in the 1950s.  It settled ONE QUARTER OF AN INCH and was closed for observation and stabilization.  While the Viaduct was closed, we could not leave West Seattle.  Traffic was totally gridlocked.  The 100,000 cars a day that used the viaduct were shunted to I5, thus making it impossible for traffic to exit the West Seattle Bridge, thus backing traffic up into the neighborhoods.
Politicians and business leaders decided that SOMETHING MUST BE DONE.  There were several options on the table; rebuild the viaduct, tear down the viaduct and build surface streets, or dig a tunnel for a new highway.  As I recall, the tunnel was voted down twice, but that was the option that was chosen.  This is a state highway, yet the citizens of Seattle were voting on it.  Eventually the state chose the tunnel.  The question of who will pay for the inevitable cost over runs is unanswered, they may be billed to the citizens of Seattle.
The project requires the use of the largest deep bore tunneling machine ever built in the history of the world to dig a two mile tunnel.  This would be a tunnel in a geologically unstable area, through fill.

What could go wrong?
  • The boring machine traveled 1,000 feet and seized.  
  • A "rescue" pit had to be dug to get to the drill.
  • Mass quantities of water have to be pumped from the pit being dug to rescue the drill. 
  • Removal of that much water is causing surrounding brick buildings to sink; foundations and walls are cracking.
  • The "de-watering" has caused the Alaskan Way Viaduct to settle TWO INCHES.  TWO!!!!  And yet, the the contractor, the Washington State Department of Transportation, and the Seattle City Council assure us that all is well.
As former Seattle citizens we follow the trials of Bertha (the affectionate name for the drilling machine) with keen interest.  There are several good articles in the independent press on the subject.  This article hits the high points of how we got to the crash site. It's worth reading if you're interested in civic dumbness.  This article is also interesting.


  1. Very interesting...I hope someone wakes up and decides on the surface/transit option.
    I just read Travels With Emma blog about the scopes containing simple binoculars. Can't believe how much I've learned this morning and it's only 8am!

  2. Interesting. Seems they've decided that's what they're doing no matter how many things happen to show that it's not such a good idea after all. Typical.