http://www.seattle.gov/Transportation/docs/Seawall%20FAQ_Final.pdf
http://courses.washington.edu/ess202/ESS_202_kramer.pdf

But don’t take my word for it, listen to what the Army Corps of Engineers have to say:

“At this time, additional information was collected regarding the condition of the Alaskan Way Seawall. The information showed that the Seawall was also seismically vulnerable and in a state of disrepair. The information also showed that the structural integrity of the Viaduct is dependent on the Seawall.”

http://www.nws.usace.army.mil/PublicMenu/DOCUMENTS/ELLIOTTBAY/Alternative_Screening_Memo.pdf

But the Nisqually earthquake still doesn’t represent the most serious seismic threat to the Seattle area. The Seattle fault, which lies approximately under I-90, last moved ~1100 years ago. If this fault moves again, it could potentially kill 1,600 people and cost $33 billion in damage and economic losses (EERI), as well as pancaking the Viaduct. This kind of earthquake has a non-trivial chance of occurring in the next 10 years.

http://earthquake.usgs.gov/regional/pacnw/activefaults/sfz/
http://www.eeri.org/site/projects/eq-scenarios/seattle-fault

The Deep-bore would most likely finish the seawall first.

Which is what Mallahan has championed as not just the “arrived” solution but the best solution. Yet you have no “advantage Mallahan”.

As Zed pointed out, McGinn is anti tunnel and doesn’t support a cut and cover option. In fact he’s expressed more support for the DB alternative if there is a tunnel at all.

And, absent an EIS how is it you know the seawall is the dominant factor in public safety. I’ve only ever heard it described as essential for preserving an artificial waterfront and for the most part no longer relevant in terms of shipping commerce. I’ve heard no claims that the demise of the seawall would result in catastrophic failure and loss of human life in the event of an earthquake.

Amen to that. There’s no sense of urgency with the McGinn crowd, just that they get their way no matter what the costs.

I’m not against the tunnel because it promotes automobile use. I see the lack of exits to downtown as a feature, not a problem. But I don’t buy into this “sunny beaches” idea of what the waterfront will look like. I see six to eight lanes of traffic, no parking, less ability to bike and much harder for pedestrians to cross. It’ll be gorgeous only for those that have views from upper story windows.

If the funding is found for a tunnel, from what little we’ve been told so far I strongly prefer the 6th avenue Seattle Tube idea that was given the bums rush. If the costs are comparable you get a lot more bang for the buck.

And for the record I don’t believe tearing it down and doing nothing or just adding transit is a viable option.

I wasn’t meaning to be trite. I imagine the concrete would fall to the ground accelerating at 9.8 m/s squared. =) I just wondered how long it will take for planning, staging, take down, cleanup, etc… once they decided to move with haste to take it down, how long would it be before those surface parking lots under the viaduct look up and see nothing but sky?

Additionally, there is certainly an active fault in the Seattle Fault, which is right around like if you drew Royal Brougham all the way from Bainbridge to Sammamish.

Seismology has in the last twenty years gone away from statistical predctions of earthquakes; i.e., based on past ones. We can now understand individual faults a lot better than just the number and magnitudes of earthquakes they have historically produced.

Seattle is at risk of a number of quakes far more destructive than Nisqually. This includes an enormous, infrequent, but possibly overdue quake from the Cascadia subduction zone ( http://en.wikipedia.org/wiki/1700_Cascadia_earthquake ). The Seattle Fault in Elliot bay could also produce quakes similar in magnitude to Nisqually, but would be devastating due to the closer proximity ( http://en.wikipedia.org/wiki/Seattle_Fault ). There are many other faults in the region which, depending on the combination of magnitude, distance and type also put Seattle at risk.

The viaduct is not the only problem. Like in California, rapid urbanization during quiet periods between quakes has created a sense of complacency. But the older areas of Seattle are full of unreinforced masonry and other building types that are particularly vulnerable. California has had a succession of medium-sized quakes in the last forty years, the combination of which has led them to retrofit similarly dangerous housing and transportation infrastructure beyond what we’ve done here. Certainly retrofits are subject to cost-benefit analysis and should preserve the feel of the neighborhood, improving it where possible. But we are way behind, and the viaduct is just the start.