Will the deep-bore tunnel — the current choice by the city and state to replace Seattle’s Alaskan Way Viaduct — go over budget?
One way to answer that question is to look at what’s happened with other tunneling projects in the Seattle area. In a new report—Cost Overruns For Seattle-area Tunnel Projects—Sightline examines the cost history of four recent tunneling projects: the Mt Baker I-90 expansion tunnel; the downtown Seattle bus tunnel; Sound Transit’s Beacon Hill tunnel; and the Brightwater sewage tunnels.
Opinions about the likelihood of a cost overrun for the deep-bore tunnel tend to fall in a pattern. Those in favor of the deep-bore project downplay the chance of going over-budget, and point to a 22 percent cushion in current budget that is set aside for unforeseen problems. Those opposed to the tunnel tend to less sanguine, pointing to international research suggesting that major infrastructure projects rarely stay within budget, even when they include such line items.
There’s a lot riding on the current cost estimates. If the project goes over budget, Seattle taxpayers foot the bill—a curious result, considering that Seattle voters rejected a tunnel replacement option by a 39 point margin. A cost overrun as small as $100 million (just 2.4 percent of a $4.2 billion project) works out to about $167 per Seattle resident—or almost $700 for a family of four. For a city struggling to avoid deep cuts to basic services, even a relatively small cost overrun could be challenging.
Of course, it is impossible to know in advance whether any project will stay on budget. And that’s especially true for a project as complex, daunting, and unknown as this one. It would be among the widest-diameter bored tunnels ever built, through a seismic fault, directly underneath some of the densest and most valuable urban real estate on the West Coast. Besides, when engineers first made the $4.2 billion cost estimate for the entire Alaska Way Viaduct replacement project—with $1.9 billion price tag for the deep-bore tunnel—they had finished only 1 percent of the design. So the current cost estimate is little more than a placeholder.
It goes without saying that no two tunnels are alike. The deep-bore tunnel will be unlike any other tunnel that has been constructed locally. Nonetheless, we can learn something by examining recent local projects, each of which grappled with specific geographic and historical issues. It is only reasonable to believe that the deep-bore tunnel will face its own unique problems. But, speaking personally, the fact that the deep-bore tunnel is something new and different makes me more pessimistic than optimistic.
Importantly, the cost estimates I’ve included here are very conservative—that is, they tend to paint the projects in a favorable light—because they use initial cost estimates that were relatively well thought-out, usually when the contracts were ready to be sent out for bidding. In some cases, the earlier and less-planned-out cost estimates were much lower; using those rougher estimates could have resulted in a much worse accounting for the cost overruns.
Will the deep-bore tunnel prove to be as inexpensive as the Mount Baker tunnel? Or will it look more like the downtown Seattle bus tunnel? Only time will tell. In the meantime, Sightline’s report, “Cost Overruns For Seattle-area Tunnel Projects,” can help inform public understanding about the actual costs of similar projects nearby.
Chris
Very timely information. I have to think that the I-90/Mount Baker tunnel benefitted from the fact that it was the second (technically third) tunnel through that soil, and that the tunneling technology was decidedly low tech.Cary Moon has reported that the tunnel plan is changing—it will be cut and cover south of Yesler, for example. I wonder if the Governor will remain so stubborn about building this thing if the more detailed engineering shows an extra billion in cost?
Jim
Eric, by your logic we should scrap plans to extend light rail as well. History tells us that it will cost more, we’ll get less and it will take longer to build than originally planned. Is that what you are suggesting? For the record, I support light rail. The initial segment and Phase Two.
bill b
…and bus tunnels and sewage projects seem like a bad idea too.My understanding is that the overrun assignment to Seattle is a red herring. The lawyers I’ve spoken to have said there is no way that would stand up in court – how could Seattle, which is not involved in the design, funding or building of the tunnel be liable for cost overruns.As this city grows to the Metro-Monstrosity that Bruce Katz, David Owen and others push towards, massive infrastructure investments will be required. Look what Seattle today is already facing: – $500M in deferred roads and bridges maintenance – a couple of $B for north end sewer capacity – Replacement of the Cedar River water supply pipeline – cost = ?And the region: – I-5 upgrades through downtown – Lake Washington bridge replacementsLarge engineering projects in the midst of a functioning city are expensive and subject to a variety of variables.Rather than slamming the tunnel project, mechanisms such as fixed price contracting or longterm profit sharing from tolls should be pursued.Note also that McGinn’s “largest tax increase in the city’s history” is really infrastructure projects the city will need to do as well.
Eric de Place
Jim and Bill B –I’m not sure I follow your reasoning.In no sense am I suggesting that we scrap sewage, rail, roads, whatever. All I’m doing is pointing out that local tunneling projects have exceeding their initial cost estimates. I think that’s valuable information to the public. What I am suggesting is that we take a a more realistic view of cost projections, particularly when a small slice of the population (Seattle property owners, in this case) is on the hook for overruns that could potentially be onerous. I’m unclear why anyone would rush to firm up funding agreements when the available cost estimates are based on 1% design—far, far sketchier than the engineering information we’ll need to put the projects out to bid. Chris—yes, the I-90 expansion through Mt Baker had a big advantage: a large adjacent tunnel, for the original I-90, had already been dug through the ridge. Also, the bored portion of the Mout Baker tunnel is about 1/6th as long as the planned deep-bore tunnel.
bill b
Note also commentary from Publicola on the cost overruns and Seattle’s liability:http://publicola.net/?p=16368
Don
Don’t forget the huge tunnel that was completed 4 years ago. They drilled a mile long 14′ tunnel underneath Mercer Street between Lake Union and Elliott Bay. The tunnel is designed to store rainwater during storms and send the water to the West Point sewage treatment plant.King County dedicates new Seattle facilities
MulliBass
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