Seattle Urbanists Should Be Rooting for the 99 Tunnel’s Success


Let’s talk about Bertha.

I didn’t live here when we debated how to replace the viaduct (SR-99). I didn’t even live here when Bertha first broke down. So perhaps I don’t have the appropriate nightmares when I hear “deep-bore tunnel.”

So when I read articles talking about how the tunnel is such a terrible investment, I wonder why people are so eager to declare the project dead on arrival. I read comments on publications like The Urbanist and Seattle Transit Blog and see people rooting for the tunnel to fail, just to prove that it was a bad idea.

But I’m looking forward to the tunnel opening because I see the tunnel as our best hope for fixing the other, bigger urban freeway in Seattle: I-5.

Simply removing I-5 with no replacement is a political nonstarter. I agree that with a fully built out rail and bus network, Seattle doesn’t need a freeway to move people in and out of Downtown. But I-5 is much more than just a way to get Downtown. It is too important, regionally and statewide, to remove the freeway for Seattle’s benefit and leave the rest of the region to just figure it out. One often cited solution is that high-speed rail (HSR) could help, but a good HSR line simply isn’t relevant for most trips on I-5 within King County, particularly for commercial and freight traffic.

Removing I-5 means we can use the broad freeway footprint for many uses, such as public buildings, green space, and rail generally, or simply developable land for a booming city that desperately needs more space for dense residential and commercial development. We can’t put all that high-value real estate to more productive use by just capping the freeway. If we are going to remove I-5 and rebuild Seattle’s urban core, something will need to replace I-5 and provide that critical connection for regional and statewide travel. That’s right–another tunnel, this time to replace I-5. Call me crazy. (I’m definitely crazy.)

I’m thinking a three-mile tunnel, between I-90 and SR-520. Maybe even tunnel under the Ship Canal if the I-5 bridge is at the end of its life and needs to be replace anyways. Will this be crazy expensive? Yes. Replacing I-5 as-is is also crazy expensive, and we can built this new tunnel while the state transportation deparment holds the current freeway together with duct tape and rubber bands.

The SR-99 tunnel can work if it has enough traffic to prove it’s useful infrastructure but not too much traffic that it’s just another part of the problem. If it can be proven as an effective bypass for people trying to get somewhere other than Downtown, then maybe we can point to the tunnel as way to convince key stakeholders–the Port of Seattle, a Legislature filled with representatives who neither live or work in Seattle but use I-5 everyday–that yes, we can remove I-5 and do without all those Downtown exits.

Get ready Seattle. I’m rooting for Bertha to make a comeback, and so should you.

Title image courtesy of Washington State Department of Transportation via Flickr.

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AJ McGauley was a temporary transplant in the Seattle area, living in East King with his lovely wife for five years before returning to the great Midwest. Having lived in nine very different cities in the six years prior to moving to Washington, he discovered the wonky side of urbanism after reading The Urbanist and is interested in why cities grow (or don’t grow) in different ways. He worked for Sound Transit and can still be found riding transit for fun.

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The main issue is that the tunnel plus surface streets planned increase the cancer of cars in Seattle streets for another generation. Seattle had a chance to be bold with a method to reduce cars to only those that were necessary. Istead, they continue to encourage superfluous traffic. Plus, they didn’t roll the tunnel.




At least the hideous viaduct will be no longer roaring through Seattle. Of course. They would have left it up for people and bikes to some degree. A people highway! Nope. Ditch that too.



You do realize that 99 via the tunnel will be able to host less traffic than the Viaduct it replaced?!

And, it cost almost twice as much to build than it would have cost to rebuild/retrofit the existing structure?

Oh. You’re new here. You probably don’t know any of that.


It’s my understanding that the tunnel acts as the new bypass while surface streets will replace the viaduct itself with their off ramps to downtown. Both together offer more capacity.


I understand. You restrict flow on the two north/south corridors. You restrict flow in the downtown core. The result is you have traffic congestion wherever you go. This doesn’t help alleviate stress for travelers or visitors/customers to the downtown area. It only builds on the poor decisions we’ve made previously.


No… There WAS a Surface+Transit option that was proposed — and it was shot down by people in power who benefit from the tunnel. The state money for the Tunnel only pays for the tunnel and the street below, which will be an 8-lane highway at the southern end. The street was already there, so it’s not any more capacity than was in the corridor before, except now much of that traffic is at pedestrian level instead of grade-separated. And any additional improvements to City streets or (County) buses will have to be borne by those government entities. That’s why it was a dumb investment.


However, the city leaders have decided Downtown needs a road diet, stifling traffic in the core. So, your plan of support for more restricted roadways only leads to more and more congested traffic. You can’t have it both ways. If you tighten all the major traffic corridors you exacerbate the problem, You don’t relieve congestion in any way.


Nothing indicates I-5 is structurally unsound and needs to be rebuilt. With good maintenance and preservation funding the existing freeway structures in Seattle should last a long time and only require occasional spot improvements.

Cristofer Horbelt

Actually, the columns supporting much of the elevated portion of I5 are of the same design as the AWV – not enough steel to resist the tension induced forces from rapid ground acceleration (shaking) that happens in larger magnitude earthquake. Although its at less risk of failure since they are founded on better soils that the fill that the viaduct was constructed on, they are still very susceptible to failure in a event that is unique to this region.
One more comment as well – Yes, we should all root for tunnels success, since we’ve already “bought” it, rooting for it’s failure is sort of a “cut off your nose to spite your face” approach. Hopefully the Urbanist will starting rooting for Donald Trumps success as well.


Fascinating! As a non-engineer I haven’t considered that. Is there a good resource specific to I-5 for further reading you can suggest? Thanks!

Cristofer Horbelt

Sorry, nothing specific. The advances in earthquake engineering and understanding, though, in just the past 25 yrs or so have led to dramatic safety improvements for new structures. In this respect, the same safety concerns apply to many of the more rigid buildings and structures constructed in the 50’s and 60’s.


A KUOW story from March 23, 2016, “Hollow Columns Holding Up I-5, I-405 Bridges Could Implode In Major Quake

Nearly 2 dozen bridges along the I-5, 405 and 520 corridor are susceptible to collapse, even in a moderate earthquake – due to being hollow.
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Michael Schuler

The premise that 99 will be beneficial “if it can be proven as an effective bypass for people trying to get somewhere other than Downtown” is interesting.

I once saw someone on Ebay selling a teak “desk organizer”: it was a napkin-holder/salt-and-pepper set missing the shakers. I’m sure that someone with a surplus of money was eventually the owner of that kludge. Maybe they even looked around for a couple more: one for holding soap in the shower, another to use as an iPad stand.

It is unfortunate that more of the R.H. Thompson expressway doesn’t still exist to serve as a visual reminder that a serious cost-benefit analysis needs to be done before money is spent.

By the way, if anyone is in the market, I’ve got a lead on teak hoverboard stand that would look great in your SLU efficiency.