Monday, May 04, 2009

Another Cable Stay Bridge Proposal

Another cable stay bridge proposal for the SR-99 viaduct replacement. This time though it's not offshore oil derrik like floatation assisted piers spanning Eliott bay. In fact it's a proposal to build it above the existing viaduct while that structure remains in use. Supposedly this idea was vetted by WSDOT and "concealed" from the public. A well respected bridge building and mega project builder did submit a proposal to WSDOT. If true this would provide 6 lanes instead of four for a quarter of the cost. I'd note though that the proposed bridge sections only span a half mile while the proposed tunnel is two miles. On a cost per foot basis this make the two about even. It's not clear how much of the additional length is taken up with the supporting "approach" bridges and how much, if any is a surface alternative.

Although the roadway would be higher it's also much wider so I'm not sure that does much to open up the waterfront. The additional width appears in the proposal to extend inland. That may end up being a bumbershoot for the surface route (a feature of any viaduct option) and for part of a large waterfront park. There's a switch, build a freeway to put a roof over a park!

I'd love to see and hear more about this option. I fear though that any such proposal would be torpedoed by wealthy condo owners downtown who's views would be impacted.

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