Seattle Seawall Replacement Could Be Back To Square One
Doug MacDonald says technically, the project would not be dead, but the gas tax increase challenged by Initiative 912 provided the majority of funding for the project.
MacDonald's comments came during a KOMO-TV interview about the Seattle seawall and the damage that could be caused by a major earthquake on the Seattle Fault.
Seattle city officials say this area does not face the threat of flooding from the same causes as New Orleans, or the threat posed by Hurricane Rita, but there is a significant water threat from an earthquake -- particularly given the level of deterioration in the Seattle seawall, which was built in the early 1930's.
The Colman ferry terminal, the waterfront fire station, and the Alaskan Way Viaduct were all built on fill.
Pictures from 1932 through 1934 show construction of the wooden sea wall. The area behind the wall was filled with sawdust, earth fill, and whatever materials were available at the time.
The soil is unstable when agitated and liquefies under sustained shaking.
If the soil liquefies, it would exert severe pressure on the seawall.
"That's going to cause the seawall to bulge out, to move outward toward the bay," said Dr. Steve Kramer of the U.W. Civil Engineering Department. "The soil behind it will follow and the foundations of the viaduct at least in some locations are going to fail."
The Capital Project Director for the Seattle Department of Transportation, Richard Miller, says a breach in the seawall is becoming more likely: "There are some marine worms called gribbles that are eating the timber that supports the seawall and the viaduct."
Miller says some emergency repairs have been made, but the city has lacked the money for a substantial fix. The estimated cost of seawall replacement is $800 million.
Gribbles caused substantial damage. The 70-year wood flakes under minor pressure and several blocks are believed to be in seriously deteriorated condition.
Seattle has upgraded the viaduct by strengthening its ability to withstand earthquakes. But engineers say if the seawall fails, that strengthening would make little difference.
Miller says it would create enormous problems: '"A lot of the downtown power comes through this corridor, so it's a transportation corridor as well as utilities. So it is very important to the lifeblood of Seattle."
Seattle has a rebuilding plan. But the state warns that plan will die if voters reject a gas tax increase.
"It is the cornerstone of the financial plan for fixing the viaduct," MacDonald said. "So, if the initiative passes, the implication for the project is we are almost back to square one."
In New Orleans, they hoped levies would hold and were wrong.
We'd be betting against an earthquake, the UW's Kramer says: "Well, you can always roll the dice. We all do that every day. But in situations like this, you have the potential for the loss of many lives."
Seattle Mayor Greg Nickels says the viaduct and seawall replacement are a key priority. The federal government did provide $200 million and the city believes it will be able to find matching money whatever happens with the "gas tax increase repeal" initiative.
But the total project is expected to cost between $2-$11 billion, depending on the plan selection, which include elimination of the viaduct with improvements to surface streets, rebuilding a viaduct, or building a tunnel to replace the viaduct. All three plans include the $800 million cost of sea wall replacement.