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Seattle's Great Viaduct Debate

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Posted by Eric de Place

02/15/2008 12:15 PM

Smart Growth America on Seattle's viaduct.

Over at Smart Growth America's blog, Cary Moon -- one of my all-time favorite gadflies -- is doing some writing about Seattle's ongoing viaduct saga. Go check it out.

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The issue is one of growth, flows, and the shape and layout of Seattle. There are but seven streets that run the length of downtown. That is why we spent a half-billion to create an eighth one, underground, for our transit system.

100 years ago our city engineer faced the basicly the same issues. Overlooked in the hard and fast stands taken by many parties involved, I think the most pragmatic potential solution has been overlooked.

Rather than replicate the current route, I would implore that all parties review R.H. Thompson's solution used by the Great Northern railroad, still used by it's successor today.

The idea starts at the north end of the current Battery Street Tunnel.

Where SR 99 turns west to enter the Battery Street Tunnel, begin digging a tunnel due SOUTH from that point. The incline would begin at the current highway level, and drill down to the level of the BNSF tunnel, as this new tunnel followed directly under the exsisting surface streets SOUTH under 6th to Westlake, then deeper still south under about 5th. You keep digging down as you go to get under the current Metro bus/light rail tunnel, then level out and pop out EAST of the existing BNSF Rail Tunnel near Main Street, between 4th and 6th Avenue.

You would build two main tunnels, 3 lanes wide each with a third service tunnel between... by following under the streets, there is no domain issues.

Exit out on the Metro Bus only lane... or east of it... and parallel with sixth avenue.
Then build exit on ramps:

-One funnels back on to I-5 south,

-One funnels east to join I-90 eastbound

-One continues on to Spokane Street or angles across the industrial area to East Marginal Way

-One last ramp that funnels into the parking for the stadium area.

When tunnel and ramps are done, then break through the wall at the Battery Street Tunnel and connect the existing 99 to the new tunnel under Seattle.

The remaining Battery Street tunnel is converted into an on and off ramp that feeds back around to the waterfront, or betteryeat, a direct ramp for Piers 90 and 91 access via Western and Elliott to get to the new ship piers, and expidite interbay traffic.

ONLY THEN do you and tear down the viaduct.

• You loose the Seneca ramp, and Western Northbound, and the 1st Ave ramp southbound... but you gain faster and direct access to I-5, and you don't have to shut down the existing viaduct for a long period of time in order to build it.
• The port gets the land adjacent to the piers from 36 south... BNSF and the port can now load ships direct to rail. Old 99 could be moved parallel to First Avenue, and reconnect with the new diversion between Lander and Spokane Street.
• The viaduct can be carefully removed, parts retained for viewing and concert platforms... and the sea wall can be replaced a block at a time to keep the waterfront working and functional...
• Best of all, Seattle gains the waterfront for parks, parking, street cars, etc, as well as a much faster second north south arterial, whose clogs bypass the city, the port gets a very efficient way to move containers.

Posted by JoshMahar 02/19/2008 12:04 PM

gicoe, I believe we already had this possibility (or something like it) and it failed. Miserably. This is a terrible idea because it totally obscures the whole point of destroying the viaduct in the first place.

Demolishing a major highway is a way of a making a statement. It is a pledge to reduce our personal vehicle use and start being smarter about our travel throughout the city.

Plus, your idea is INSANELY expensive. Build a SECOND tunnel through downtown. Hmmm, here's a concept, why dont we just start USING the one thats already there. Take the bus. Take light rail (in a few years). If we get people to do that I think we can save the money from the tunnel and pump it into making that waterfront beautiful.

"The viaduct can be carefully removed, parts retained for viewing and concert platforms"

THAT is a great idea though. I would love for them to keep sections of the Viaduct intact, for example, the off-ramp at 1st and Spring. How awesome of a viewing spot would that be.

Posted by glcoe 02/21/2008 02:53 PM

Hey Josh,

With all due respect, of course less is best. However, my understanding was the first tunnel idea was to replicate the route the viaduct currently takes... A HUGE expense given that the entire area has major business and transportation impacts, plus the entire waterfront is built on unstable fill dirt, with bedrock more 40 to 70 feet below the surface. Lastly, the viaduct traverses 7 earthquake faults.

Tunnels are expensive, but so is the lack of flow. Including Metro, Rail, Sewer overflow and utility tunnels, there are currently more than 85 tunnels in, around and under Seattle.

Any Surface option requires the 100,000 plus daily users to find alternates, and not all can bicycle or take a bus (Seattle is the 5th busiest port in the USA for Containers, and numbers continue to rise).

Basicly there are three choices.

1) Rebuild the present on (ugly, impacts locals for 3 years, and keeps the waterfront shut off from downtown)
2) Go Surface with better syncronized lights, and a major arterial. Again, challenges to access to the waterfront. Increases traffic in town, and access for pedestrians remain
3) Tunnel under... Hugely expensive if done as initally proposed. The point of my post is that the idea presented here would cost about the same as rebuilding, would give the city a solid route, and keeps the impact on waterfront business and movement of bulk cargo at the most minimum.

And yes, basic trip reduction, etc is still the best, BUT we are talking about infrastructure that hopefully would last 50 to 75 years... Temporary diversions such as what we did during the I-5 lane closures are just that. Numbers crept up as the project went on, as did the back ups.