The West Seattle Bridge was just 36-years-young when it cracked, sagged, and threatened to collapse, adding another layer of pollution to the already highly polluted Duwamish River. The city grappled with what to do: repair or replace. Yesterday the Seattle Department of Transportation (SDOT) released its cost-benefit analysis revealing a replacement option scored highest: “Alternative 4 (superstructure replacement) was the overall best performer.”

Normally 36-year-old bridges don’t need replacing, but these are unique circumstances. Although messaging has varied since the bridge closed for emergency shoring in March, SDOT has highlighted how expensive and uncertain repair could be. A repair bridge could last 15 years or a lot less or more. It’s hard to gauge. One the thing the agency does know is that a repaired bridge would need constant tending and expensive maintenance on a yearly basis to keep it from deteriorating once more. In fact SDOT’s consultant WSP put the price tag at approximately $916 million to quantify the lifecycle costs of repairs over 79 years.

Alternative 2 (repair) and Alternative 4 (superstructure replacement)both costs around $1 billion, but more of that is upfront for 4.
The cost-benefit analysis eliminated Alternative 3: partial replacement for feasibility concerns. (SDOT)

Publications like The Seattle Times and West Seattle Blog highlighted that repair would cost “only” $47 million upfront in their headlines and coverage. But that overlooks how expensive it will be maintain the repaired bridge; the millions in annual maintenance clarify the city’s decision. Better pull off a leaky band-aid and get stitches than slowly be bled dry.

SDOT finances are it too sorry of a shape to throw good money after bad trying to put an ailing bridge on life support. Bridge maintenance costs could end up swallowing up the rest of the SDOT budget–and rarely are there grants for maintenance–which jeopardizes investment in infrastructure for people walking, rolling, biking, and riding transit.

Replacement isn’t cheap either and requires more money upfront, but it offers more certainty. WSP puts superstructure replacement at $1 billion total with $383.1 million upfront. The other replacement options–full replacement and the immersed tube tunnel are even spendier with the immersed tube requiring almost $2 billion upfront. The immersed tube is complicated by environmental factors–the Duwamish River is a superfund site and disturbing the riverbed could release more pollution.

A newly designed replacement bridge opens up the possibility for multimodal improvements, which could allow the City to make major progress on its long-term transit and climate goals. That means fewer car lanes, as we’ve already argued as a citywide bridge policy, and adding space for light rail. This could save a ton of money on Sound Transit 3 and open the door to accelerating West Seattle Link even as the recession eats into Sound Transit revenue.

SDOT has suggested it may be able to replace the bridge in just three years using an accelerated planning process and bridge span partially constructed off site. This would require bypassing the environmental impact statement (EIS) process, a privilege basically never bestowed upon biking and transit infrastructure. In this case, since there are cars to move, the City appears ready to move mountains. That’s too bad since car emissions make up the biggest chunk of Seattle’s carbon footprint by far.

We’re doubtful three years is actually doable, but replacement is still the best option. Light rail adds another layer of complexity in planning, but SDOT doesn’t need to wait for the whole light rail extension to be planned to move ahead with a light rail compatible bridge. It needs only confirm the bridge could link with the two adjoining stations and fit the alignment. The cost-benefit analysis confirmed that SDOT has already started those conversations with Sound Transit.

Sound Transit’s alternatives all branch off south of the West Seattle Bridge’s to serve Delridge Way and Avalon. (Sound Transit)

But what about a West Seattle light rail tunnel you ask? Well that ship has sailed unless Seattle is prepared to raise hundreds of million of additional dollars on top of a similarly large amount of money needed to fund the West Seattle Bridge replacement.

Mayor Jenny Durkan’s decision around the West Seattle Bridge had been expected this week. She has delayed that decision, but the choice is clear. Let’s build the bridge of the future instead of pouring money into the freeway of the past.

The Editorial Board consists of Natalie Bicknell, Ryan Packer, and Doug Trumm.

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The Urbanist was founded in 2014 to examine and influence urban policies. We believe cities provide unique opportunities for addressing many of the most challenging social, environmental, and economic problems. We serve as a resource for promoting and disseminating ideas, creating community, increasing political participation, and improving the places we live.

18 COMMENTS

  1. Has anyone asked West Seattle residents and their advocates whether they would accept a bridge alternative — repair or replace — that reduces car capacity? My guess is the residents would say no, although Urbanists and transit advocates might think that is a good idea.

    I would start with the W. Seattle community and what they want in a bridge, considering they live there and know what is the best mobility for them despite ideology. If reducing car capacity is not an option then repairing the current bridge is the best solution, and really only affordable option at this time anyway.

  2. You assume that it would save money to run light rail on the West Seattle Bridge, despite any evidence. The new West Seattle Bridge would make up only a tiny piece of the overall route of light rail to West Seattle. It is highly unlikely that using this one segment would save Sound Transit any money.

    While the West Seattle Bridge benefits everyone, it benefits single occupancy vehicles the most. Transit can still make that crossing using the lower bridge, as can freight. It is slower than using the high bridge, so the high bridge would benefit transit right now. However, in 20 years, no buses will go over the West Seattle Bridge. Thus the only people who benefit from a longer lasting bridge are drivers. Not transit riders, not bikers, not pedestrians, not even freight — only drivers of passenger cars.

    Your support of the replacement option is bizarre. You are asking for a far more expensive solution that will only benefit passenger cars. It will cost a lot more and take longer — which means that transit riders would actually be hurt more (not as much as drivers, but still more than the cheaper option).

    The obvious solution is to repair the bridge. It won’t last as long, but it isn’t clear whether it will be essential forty years from now. By then Link will provide for *all* the transit to the peninsula (whether it makes the most sense or not). The lower bridge could be reserved for freight, while regular drivers just go around. Even if the bridge is replaced 40 years from now, that might still be cheaper in the long run. The bridge should be repaired (and tolled).

  3. If the bridge can be repaired, it would allow for reopening quickly. If not, we need to rebuild quickly, but adding Link will not be trivial as the approaches need to be reconfigured. That would slow down the rebuilding effort. SDOT made it very clear during the meeting on Wednesday, that they would like to focus on replacement and not add any complexity such as Link to the project.

  4. West Seattle is not suitable for light rail. The gradient is too steep for trains and it’s location is a dead end. The proposed tunnel is an expensive solution for a steep slope. Yet the fact would remainthat there is no way to continue this line beyond the Junction limiting its income.
    Delridge way is a natural rail corridorf. It also has the potential extend to Burien, the airport or Tacoma.
    An aerial tramway is the consensus design for steep lopes and short routes. A route from 35th, along the side of the golf course to Delridge would connect West Seattle to a light rail line that would link to downtown or south to the airport without going through town.
    Adding a roller coaster ride over .a high bridge and up the Avalon slope with the added cost for the increased structure is not the way to get light rail to West Seattle.

  5. In alternative 4 the only way for light rail to run up to the replaced high bridge is on top of the 40 year old approaches running at 6% grade that SDOT doesn’t have any idea if they can handle rail. And those approaches would need to be completely reconfigured to maintain the 99 and Delridge ramps. You’ve just made the project twice as complicated. And supporting rail in alternative 4 reduces traffic lanes by roughly 40-50%.

    An entirely new bridge (option 5) is the only realistic way to allow light rail to connect to the high bridge by having the south side jettison out from the existing approaches and the separate light rail approaches could “plug in” there.

    Even if alternative 4 can physically support rail over the 1300 foot replaced high bridge, it practically doesn’t work because of the approaches.

    • I’m confused where the idea that light rail can’t handle 6% grade is coming from? That’s not all that steep and rail systems around the region and world handle such grades routinely.

      Our point is that we shouldn’t assume we need 7 car lanes. We’ll increase the capacity of the bridge overall by dedicating a couple lanes to light rail.

  6. Each alternative costs out what it would take to provide a bridge until the year 2100. In the scenario of alternative 2 the initial repair cost is 47 million then there is slightly higher maintenance costs but the big cost is the eventual replacement of the bridge in the year 2062. That’s what causes the price tag for alternative to to be 916 million. It also includes a credit for bridge life beyond 2100.

    This eventual replacement is noted in their timeline and a large expense is highlighted in the repair and rehabilitation cost. The footnote at the bottom of page 4 states “alternatives one and two each assume two phases of construction. One for the initial storing or rehabilitation; one for the eventual replacement.”

    In this analysis all costs are in 2020 dollars. It does not account for inflation nor discount future spend.

  7. Regarding your statement: “ In fact SDOT’s consultant WSP put the price tag at approximately $916 million to quantity the lifecycle costs of repairs over 79 years.”

    That 916M cost includes the cost of building a new bridge in 2062. To characterize it as just the cost to repair is wrong.

    Alternative 4 is just a replacement of the superstructure. It reuses the existing piers and foundations. There’s no way to add light rail to that design given the approaches. To add light rail (and there’s no data suggesting that would be cheaper) you need to go with a full replacement which is far more expensive. Adding light rail would be even more so. And you’d need to likely rebuild the East and West high rise approaches.

    This editorial is making a completely unsupported argument that building a entirely new bridge with room for light rail would be a more cost effective solution. There’s just no data to support that and ignores that this concept greatly enlarges the scope, risk, and timeline of the project for both cars and transit. SDOT and their consultants know this too and are only talking with Sound Transit to keep the urbanist crowd from throwing a fit (similar reasons for exploring the quite obviously bad tunnel concept).

    • I see no indication the 416 million includes the cost of a new bridge in 2060. Just think about it for a minute a new bridge right now is costed at 564 million up front in todays money. If we assume a new bridge must be built 40 years from now with an average inflation of 1.75% it would cost $1,128,900,901.56 upfront in 2060. Unless this study believes the cost of bridge construction costs will drop so dramatically that it can somehow wipe out 40 years of inflationionary growth.

      I think what’s happening is someone appears to be playing math games with the “Salvage Cost” computations on page 54. They’re apply a “discount” based on how many years of service life an option will have by the year 2100. The full replacement is rated to last 75 years so it has a near zero value in 2100. Option 2 repair and then replace in 2060, however would have 35 years left on its new bridge (75yr rated) which nets it a deduction of 637 million. Which appears to be the missing inflationary gain I talked about above.

      This math trick gives option two the appearance of a lower total cost because apparently time ends in 2100 and we all be refunded the remaining balance of our infrastructures lifespan. It’s total BS.

      So really the real lifetime costs of the options without this mythical “salvage value”

      1. 1,683 billion
      2. 1,554 billion
      4. 1,006 billion
      5. 1,558 billion
      6 3,038 billion

    • You are also mistaken about light rail compatibility. The cost-benefit analysis states “The Forward Compatibility attribute assumes that the existing 6 percent approach grades can accommodate future Sound Transit light rail.” Furthermore on page 10, the CBA states “Alternative 4 would require a retrofit concurrent with superstructure replacement. Alternative 4 would be future compatible with light rail and restore traffic to its original capacity.”

      • You are still assuming that running light rail on the bridge would actually save money. There is no reason to believe that. Even if it did, the light rail plans would be much worse. The Delridge stop would literally be part of the freeway. That would eliminate any hope of walk-up riders, and would make it that much more annoying for those on Delridge. There you are, on the bus, very close to the freeway, but instead of having the bus quickly and easily get you to downtown, it deviates, and lets you off underneath the freeway, where you then take an elevator up to wait for the train.

        Meanwhile, what about the rest of the line? The freeway ends at 35th. Are you saying that the light rail should just run on the surface? That would save money, but it would mean it would stop for traffic lights. Even if you run elevated, the stops won’t be as good as what ST proposed. So even if you saved money (and it isn’t clear you would) the stops would be worse (with the exception of the one at the Junction, which would be the same).

  8. The chance of failure in the next 40 years is listed as 5% or less in the CBA by the WSB (the engineering firm that authored the CBA) and confirmed by the TAP (the Technical Advisory Panel – basically every expert in the state). Do you really think we should throw away a bridge that should last another 40 years and leave West Seattleites and businesses isolated for extra years unnecessarily? It seems unconscionable to me that you waste upwards of a billion dollars today, when clearly we have a budget shortfall and lots of real needs for our tax dollars, when we’re supposed to have light rail connected to West Seattle in 10 (probably 15) years. Let’s not treat this bridge like another thing American’s just throw away for a shiny new thing. This is not an opportunity for urban experimentation, it’s an opportunity for people to act like grown ups and face their responsibility.

    • No matter what course is chosen, we will need to develop a comprehensive transportation and economic development plan for West Seattle in the interim. We should take this opportunity to plan the transportation system we need for the next 75 years, and implement it today.

      Instead of rebuilding car infrastructure in the middle of a climate crisis, we should accelerate the West Seattle light rail and invest massively in small businesses, social housing, and non-motorized transportation. West Seattle residents should be able to meet most of their needs on the peninsula, with efficient transit for connections throughout the region.

      • Yes, we need a comprehensive solution, the bridge failure has elevated the urgency for a public transport alternative. But light rail would be quite disruptive for an established, dense neighborhood like WS. Gondola technology can handle hills much better at much lower disruption.

        • Wait, what?? West Seattle a dense neighborhood? Sorry, but West Seattle is not densely populated — quite the opposite. This — along with other issues — make it a bad choice for light rail. It also makes it a poor choice for a gondola. Only a tiny portion of those who live in Seattle could use the gondola stop (or stops). So everyone else would just ride a bus, and transfer. It would be much faster for those riders to just stay on the bus, even if they took the lower bridge (let alone the upper one).

          It takes 15 minutes for a bus to get from The Junction to downtown (using the lower bridge). It serves three stops along the way in West Seattle, and several stops in West Seattle. As the crow flies, it is over 6 kilometers from the Junction to downtown. The fastest gondolas are about 6 meters a second, or 21.6 kmh. That works out to over 16 minutes. You haven’t saved any time, and this from one place in West Seattle to one place in downtown Seattle. You could go to SoDo, but that means a 14 minute trip. By the time a rider gets on the train to go downtown, the bus would already be there. Again, this is assuming just a lower bridge (the bus is faster on the upper bridge).

          No, sorry, what makes the most sense is BRT. Add a new bus tunnel, changes to the bridge to avoid the bottlenecks, along with a direct connection to the SoDo busway. A bus would leave West Seattle and not encounter a traffic light until Elliot. It would not encounter congestion until Ballard (it would run in bus lanes from West Seattle to Ballard). This would provide better transit for the vast majority of West Seattle riders. Of course, it would require fixing the West Seattle Bridge.

          • Anyway, that won’t happen. We won’t have a gondola, and we won’t have a new bus tunnel. We will have light rail, even though it doesn’t make sense there. That is just the way Sound Transit rolls. They love light rail, even in areas where it clearly makes no sense (e. g. Issaquah to Bellevue, Fife or Ash Way). Freeway stations in suburbs are always a bad value, and these will be no exception. In contrast, West Seattle Link — as bad as it is — will seem like a brilliant idea.

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