Read a Pacific Northwest, liberal perspective on world, national, and local politics. From majestic Redmond, Washington - the Northwest Progressive Institute Advocate.

Tuesday, January 13, 2009

Tunnel to replace viaduct after all?

After years of wrangling over the Alaskan Way Viaduct, our elected leaders have finally reached an accord on what to replace it with:
Gov. Chris Gregoire, King County Executive Ron Sims, Seattle Mayor Greg Nickels, and Port of Seattle Chief Executive Officer Tay Yoshitani Tuesday formally announced their agreement to replace the highway along Seattle's central waterfront with a deep bored tunnel under downtown Seattle.

The pact stems from a year-long study of solutions for replacing the central section of the Alaskan Way Viaduct. Officials said thousands of hours of technical analysis, public meetings, and letters and e-mails from the public, interest groups and local jurisdictions were considered in the decision.
The idea of a tunnel has been declared dead so many times (and then revived) that this morning's announcement is comical, in a way. Given how controversial the project is, we can hardly consider this deal to be final (hence the question mark in this post's title), but it certainly is remarkable to see such a consensus between the state, city, county, and port on this project.

To be fair, this is not the same cut and cover tunnel that had originally been proposed under Alaskan Way, which was overwhelmingly rejected by Seattle voters in a March 2007 "advisory" vote. This proposal calls for a deep bored tunnel dug under downtown, running under 1st Avenue for 1.7 miles. We're happy with this proposal if - and this is a big if - we can find the money to pay for it.

Otherwise, we need to be looking at surface+transit.

$4.2 billion is a hefty price tag. But a tunnel would be a good investment.

It would preserve arterial speed on Highway 99, open up Seattle's waterfront, and move traffic underground, significantly reducing noise and pollution.

A tunnel would also be very safe.
Contary to what you might think, structural engineers agree that tunnels are one of the safest places to be during an earthquake because the tunnel moves with the earth. Tunnels are inherently strong – for example, no Seattle area tunnels were damaged during the 2001 Nisqually earthquake. These include the I-90 tunnels (Mt. Baker and Mercer Island), Battery Street Tunnel, 3rd Avenue Bus Tunnel and the Burlington Northern Tunnel.
It's bridges and viaducts that are unsafe places to be during an earthquake. Not tunnels. Tunnels are engineered to be safe.

The likelihood of a strong earthquake shaking Seattle sometime over the next few decades is very good. It makes sense to construct a structure that's going to be able to withstand that quake and remain intact.

Tunnels in San Francisco and Los Angeles served as vital lifelines in the aftermath of the Loma Prieta and Northridge earthquakes years ago. A tunnel under 1st Avenue South in Seattle could be a vital emergency arterial through the city in case of disaster. We have the Downtown Transit Tunnel but it's not as long and it would be harder for emergency vehicles to access.

The deal that our elected leaders have worked out now likely hinges on the state's ability to get federal money for the project. If Congress will agree to provide, say, a billion dollars or so for the tunnel, then the project could move forward. If federal money isn't forthcoming, this deal may have to be scrapped.

In that case, the city, state, county, and port will simply have to figure out how to make a surface only option work, because we can't have an aerial structure along the waterfront. There are obvious advantages to having a tunnel for thru traffic, but we can't bankrupt ourselves trying to fund the construction of one megaproject. We already have a serious revenue shortfall problem.


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