35 Replies to “From the Archives: SR 520 vs I-90”

  1. I can’t say as I see any problem with that analysis. Perhaps some time in the future rail transit across 520 will be a possibility, but not in any time frame that would be useful for East Link. The schedule and funding of the 520 replacement project is far too uncertain to plan a rail line around it.

    Those opposing the I-90 alignment of East Link need to realize stopping East Link from using I-90 means killing East Link as part of ST2. Now some may be happy with that, but some like Rep. Deb Eddy who seem to support building light rail on the Eastside and the redevelopment of the Bel-Red corridor need to educated as to this harsh fact.

    A stand-alone light rail line on the Eastside is simply not in the cards. Even with far more generous criteria for Federal grants I doubt the East Link would qualify without the connection to Seattle.

    1. No, Eddy is well aware that her actions will kill eastside light rail. I think what she doesn’t realize is that she’ll be run out of town when U Link opens and people are begging for more, when it becomes clear that she, Judy Clibborn, Fred Jarrett, and a few others are why East Link will be stalled.

      My goal is to make sure their names are written in fifty foot high letters next to any failure of East Link. Sound Transit has done their job – if certain legislators want to handle the anger of their constituents, it’s their funeral.

      1. You really do think that everyone sees light rail as a good thing that they want to have near them. This is not the case. There are many people who simply do not want to ride transit, even light rail, no matter what. There are people who drive in Manhattan, a larger percentage than you might imagine.

        To anyone who hates sound transit, and there is no shortage of them, killing east link is a good thing, and these voters will reward, not punish legislators who kill the east link project.

        Now, we know from the ballot results in 2008 that a majority on the east side (slim majority) voted in favor of ST2, as such, we can expect that legislators who kill east link would suffer a political loss (albeit a narrow one) IF east link were the ONLY voting issue for east side residents. It is simply not. You may be a single issue voter, but the vast, vast, vast majority of people in this region are not. Furthermore, people who hate certain projects are generally more likely to vote on the basis of that issue than people who support those projects, unless they personally stand to make millions off of a particular project, which simply does not apply to a big enough number of people to matter.

        While there may be more people who like ST than hate it, of the people for whom this is a voting issue, anti-ST voters probably outnumber pro-ST voters. But even that doesn’t really matter because both of these groups are completely dwarfed by the people for whom ST is not the deciding factor in their vote.

  2. As a somewhat frequent traveler on the UW-Bellevue corridor, I would have to say a line over 520 would be amazing. However, is this really an issue? Do people really think that a UW-Bellevue line would be more populated than a Downtown Seattle-Mercer Island-Belleve route?

  3. I think eventually you need both, but I-90 LRT is the only one that makes any sense right now.

  4. There’s nothing wrong with the I90 alignment. COB suggested alternate picks up all the good things along that route. See how good things happen when you don’t buy into the ST multiple choice test paradigm. My concern is that at best the bridge will be 37 years old when the link opens. Reality tells us the date will slide since the DIES has already slide a year from the projections in 2006. None of the floating bridges has of yet lasted 50 years. In a few years SR520 will be sailing into those uncharted waters.

    One of the primary rules when designing critical networks is to avoid single point failure. ST has built in multiple single points of failure. Start with everything getting routed through the downtown bus tunnel. Add on a aging pontoon bridge. I’m not a fan of the ferocement sailboat approach to bridges to begin with but one that’s over half way to Davey Jone’s locker and land locked between two others is sort of like a Dave Eyman initiative; built in failure to assure job security.

    If you want another single point of failure look to the Hiram Chittenden Locks. A breach like say; earthquake, structural failure of a century old Army Corp of Engineers project, navigational accident ala West Seattle Bridge, sabatoge… will severe all east west Lake Washington routes. I know the mantra about single seat rides (which assumes that where you want to go is on that single route) but all major transit systems that have proven successful (NY subway, London Tube, Paris Metro) have cross connectivity.

    1. No, all rail lines have single points of failure. London Tube fails just the same as Paris Metro just the same as Link if the line is severed.

      Or are you trying to pull out the ridiculous ‘because we’re only building one line right now, we won’t have redundancy’ argument? That’s an argument for building it and then building five more, not an argument for *not* building.

      [deleted, ad-hominem] This technique is also called ‘fear, uncertainty and doubt’ – and I think most of the readers of this blog recognize it for what it is.

      [deleted, ad-hominem]

      The Circle Line in London has four other lines sharing track with it. If part of the Circle goes down, the Bakerloo AND the Hammersmith & City lines can go down, or the District line can. For you to claim that Link is somehow different than this is simply bonkers.

      [deleted, ad-hominem]

      1. No, Ben, this is not an argument for building one giant line than building 5 more lines later. It is an argument for spending some extra money up front to reduce the points of failure on the line we are currently building.

        NYC quad-tracks every one of their subway lines. That not only increases capacity, allows for express service and local service to use the same right of way and allows them to run trains 24-7, it also significantly increases the resiliency of the system. While a subway line can still fail if a disaster collapses an entire tunnel, that kind of disaster is much less common than a technical hiccup that disables a single set of tracks.

        A second way of increasing resiliency would be to build a second tunnel through downtown Seattle, reducing that point of failure. We need to do this anyway for Ballard to West Seattle light rail, conservative resilient planning would opt to build this portion of the line first before extending the single line to Snohomish County. In fact, we’d build the entire west side line and reconnect to the main line at Northgate and Sea-Tac, creating full redundancy of the entire central system BEFORE we extended the system to Shohomish county and Federal Way.

        Now, of course there is a political reason not to do it this way. That reason has to do with sub-area equity and a general feeling among politicians from outlying areas that they would rather have a fragile system now than a robust system later. This is a reasonable tradeoff, but it is also completely reasonable for Bernie to point out the inherent risk that comes with taking such an approach.

        While I doubt that Bernie was advocating the position that we would be better off building nothing than building a fragile system, such a position is not completely unreasonable. So long as we don’t build Link, we are not dependent on Link. The plan has always been to build incredible amounts of density around the light rail stations and to provide much less parking. These communities (and eventually even downtown Seattle as well) will be completely dependent on Link for their transportation needs. If Link were to suddenly break down, they would be cut off. They would not reasonably be able to use cars instead because many of these residents would not even own cars and even if they did, there would not be enough parking to accommodate them. The only possible solution would be to deploy hundreds of buses to serve the demand, but we don’t have hundreds of buses sitting at a giant bus barn somewhere ready to deploy. These buses would likely have to be diverted from other routes, creating a cascade of difficulties.

        Remember, given how fragile our system is (built with virtually no redundancy), the entire system could be shut down by something as simple as a severed wire or a medical emergency on one of the trains. It would not require anything as calamitous as a tunnel or bridge collapse.

        This fragility also makes upgrading the system extremely difficult. Imagine someday we want to switch technologies, say to heavy rail, or we decide to bury the Rainier valley segment, or we decided we want to connect a new line to an existing line. There would be at least a short period of time in which we would have to shut down a particular segment, “unplug” it and then plug in the replacement segment. This cannot be done safely in a matter of days. It would take at a minimum a matter of weeks and probably months. Since the region will be completely dependent on this light rail system, shutting the system down will not be an option and thus certain upgrades will likely be off the table even if the money and the political will is found.

        You are free to argue that these are acceptable risks in order to get the system built quicker, but pointing out these risks and arguing that they should be considered is not in any way dishonest fear-mongering and you suggest that it is.

    2. Bernie,
      AFAIK the I-90 span has a projected lifespan well in excess of 50 years. The old span next to it was being renovated to carry the Eastbound lanes of I-90 before it was sunk due to a combination of ineptitude, bad decisions, and bad luck. I doubt renovation would have been part of the plan if the pontoons had been expected to wear out soon. In any case I don’t remember it having the problems needing almost constant maintenance that 520 has had for the past 20 years.

      If it wasn’t for the linked concrete barges across the lake we wouldn’t have any direct link other than ferries. Unfortunately Lake Washington is a tad too deep and too wide for somewhat more conventional bridge building methods.

      Do remember that NYC, London, and Paris all started with a single line, then two, then more. The cross connectivity wasn’t there from day 1. Similarly with Link the cross connectivity will come as the system is expanded.

      1. > Unfortunately Lake Washington is a tad too deep and too wide
        > for somewhat more conventional bridge building methods.

        That’s just plain wrong. BTW WSDOT has corrected their nonsense about the Lake being 400′ deep. It’s ~200′ where the ideal tower location would be which is exactly the same as the Tacoma Narrows without the problems of tides and current. It comes down to a matter of cost, not even cost effectiveness. The most expensive single suspension bridge to replace SR520 (replaces both the floating portion and the approach causeways) would run around $7B. It was thought the money couldn’t be raised for that although now we’re looking at an excess of $6B for the corridor; about double what it started out with on the cheap. But instead of a better bridge we’re getting lids and extra connections to dump more cars into the U dist.

        The reason I90 isn’t seeing the maintenance issues with 520 is that it’s 26 years newer. A decade after light rail opens it will be just as sorry as SR520 is today and the public will be left with trying to figure out how to replace it. Since SR520 won’t have room for rail or any capability to connect on the Seattle side (not to mention the ROW fights on the eastside) that option is wiped out leaving no connection during replacement and the same single link when reconstructed.

      2. Wasn’t the Tacoma Narrows bridge built around $700 million dollars? How much longer is I-90 and 520 vs. the Narrows that it would make the price so excessive?

      3. And here is the data on Lake Washington if you trust the data on Wikipedia =)


        The new Narrows bridge was listed at $849 million dollars but the project came in $114 million dollars under budget for a actual price of $735 million dollars. The depth at the towers is 150 feet with a 7 knot reversible current and the towers can support a second roadway or light rail. The overall bridge length is 5,413 feet long.



        The I-90 bridge is slightly longer at 6,620 feet for the Eastbound bridge and 5,811 feet for the Westbound bridge.

        The SR-520 bridge is the longest at 7,578 ft long.

        The current longest suspension bridge in the world is the Akashi-Kaikyō Bridge

      4. The floating portion of 520 would be about 2000′ longer than the Narrows (7000′ vs 5000′) which would place in on par with Golden Gate. However, to span shore to shore would be more like 12,000′ which places it along side the Akashi Kaikyo Bridge in Japan which is the longest in the world (also built across open ocean). There are engineering solutions they’ve just never been seriously looked at by WSDOT. An island in the middle of the lake would require something on the order of 8 million cubic feet of fill, the concrete in the existing bridge is ~7 million cubic feet. Two Narrows bridges = $1.5B. Two islands could likely be built with less fill and a single suspension span combined with cable stay or causeway approaches.

        It’s a finance and engineering problem, not an impossibility which is how WSDOT likes to dismiss hard work like… finance and engineering.

      5. Bernie, Akashi Kaikyo was $5 billion in construction costs for the bridge alone. We have a significantly different environmental situation, so anything like that here would be much more expensive. We also have a Montlake connection – as the state and region aren’t particularly interested in losing that connection, that adds even more.

        It doesn’t pencil compared to the options on the table – and that’s without islands an order of magnitude larger than the concrete fill on Akashi Kaikyo’s piers.

      6. The $6B for the corridor also includes HOV work on the eastside and the Portage Bay expansions.

        That $7B for a bridge came at a lower level of design completion than even the $3B estimates for 520. It would, too, balloon.

      7. Bernie,
        When I said “I don’t remember it having the problems needing almost constant maintenance that 520 has had for the past 20 years” I was referring to the old Lacey V. Murrow which at the time it was shut down for renovation was nearly 50 years old.

        I do not believe the Homer Hadley bridge (the one that will carry East Link) is going to need replacement in 27 years. There are a huge number of factors in bridge design lifetimes, the particular basic form of bridge construction being only one of many.

      8. The old Lacey Murrow bridge was undergoing a major refit when it sank. Cashing in on the insurance money and getting a new bridge out of the deal was the best thing that could have happened for Washington. 27 years from now the Homer Hadley bridge will be in the same position as 520 is today; it will be approaching end of life and the clock will be ticking on replacement before failure.

        One factor that’s rarely brought up is that increasingly strict standards for highways and bridges shorten the effective life of existing bridges. So yes the bridges of today are better than yesteryear but the additional stress of trains and ever increasing safety standards make it doubtful the Homer Hadley will ever meet the stated 70 year design life.

      9. Bernie,
        I don’t buy the “WADOT sunk the Lacey V. Murrow on purpose” conspiracy theory. In any case despite the age the old span never had the problems the 520 bridge started having in the 80’s. I suspect the problem of the 520 bridge is more one of building it on the cheap, shoddy construction, and inadequate maintenance.

        WADOT has an expected 100 design life on the Homer Hadley bridge. In any case there likely will be a maintenance base (probably MF1 or MF5) along East Link by the time bridge replacement becomes an issue.

        Frankly this really isn’t even a topic that needs to be discussed. The options at the moment are build East Link over the I-90 bridge or serve the Eastside with BRT and express buses. An I-405/BNSF alignment South via Renton and Tukwilla isn’t on the table. A SR 520 alignment isn’t on the table. Perhaps at some point in the future those will be options under consideration, but we’re likely to all be in the retirement home or dead by the time they would open.

        If you want East Link replaced with BRT and Express Bus service, fine then say so. If you really want rail on the East side then fine, but realize the initial segment is going to need to cross I-90 if it is going to be built at any time in the next 15 years.

      10. I don’t buy the conspiracy theory either. It just happened to work out to the advantage of Washington State. Sometimes insurance does pay off.

        If there was a will to really explore rail over SR520 then now is the time. You’re right that the next opportunity will be long after we’re gone. I also agree that the most likely scenario is for light rail on I90. But it’s not a given as it’s no where near the point of actual construction or even final planning. If it becomes apparent soon that I90 isn’t going to work (funding, physics, politics) then we still have the opportunity to look at actually designing a 520 bridge from the outset to include light rail. If East Link starts to look like the schedule will drift 5 or more years behind a 2020 opening then investment in any rail to the eastside becomes dubious.

        I can’t find the WSDOT info on design life for the floating bridges. I’ve gotten different answers from saying it was a 50 to a 70 year design life for the new SR520. WSDOT standard is 75 years but that doesn’t apply to special projects like the Narrows. Suspension bridges typically have a 100 year design life. I do remember seeing something about a 100 year design life for I90 but I think it was confusing design for a 100 year storm with design life.

        Here’s an article that shows retro fitting for light rail is not a slam dunk:


        Some points that should give pause:

        …it is not economical with current knowledge to build for extreme conditions

        I think they’re specifically referencing the Hood Canal bridge here which unfortunately is positioned to receive maximum exposure from prevailing storm tracts (winds from 210 degrees SW ).

        Floating bridges should be treated as a marine vessel.

        The analysis showed that LRT loading combined with the 1-year storm loads produced stresses that were 97% of the allowable stresses

        Does that mean closures to rail during wind storms to prevent exceeding allowable stresses? Cutting it mighty fine here at 97% using average storm loads. I think there’s ample data to suggest storms are going to become more frequent and severe due to climate change. But hey, Rush Limbaugh says global warming is a myth so what do I know.

      11. There are two things here that I think you misunderstand.

        97% doesn’t refer to what the bridge can take. It refers to what the bridge can take before we decide to close it. We’ll be closing the bridge due to high winds more than once a year whether Link is on it or not.

        Yes, storms will get worse. And when they do, we’ll build a better bridge, just like everyone does when bridges need to be replaced. But that will happen whether Link is on it or not.

        We already figured out we can build on I-90. We did two studies. Judy Clibborn pulled it out during a hearing trying to claim there were problems, but the IRT rebuffed her and said there were no blocking issues.

        I know you *want* rail on 520. That doesn’t mean it’s going to happen. I really suggest you just quit worrying about it.

      12. Interesting. Might be worth investigating somewhat more conventional bridge building methods (cable stay, suspension, etc.) for the 520 replacement. If nothing else it might give the Seattle area a nice signature bridge. ;-)

        Also makes me wonder if a floating bridge was the right choice for the Hood Canal Bridge replacement.

      13. If they did they also did a pretty thorough job of hiding it. There was some lip service from WSDOT to the idea of a cable stay bridge for the portage bay portion but it was never actually formalized.

      14. A suspension bridge for 520 would have been very difficult.

        • The water is so deep that the suspension span would have to be basically the same length as the current floating span, ie, the suspension supports would have to be on either side of the floating portion. This would mean the suspensions span would be about 15% longer than the longest suspenion span on earth today.
        • In order hold that bridge in place, the suspension supports would have to be more than 600′ out of the water. That’s 33% taller than the tallest building in bellevue and nearly as tall as the space needle.
        • The soil is so sandy and weak at the bottom of the lake, that the supports would have to go more than 100 feet into the ground, and the ground there is already 200′ under the water. So the entire support would be more than 900 feet tall, or as tall as the columbia center.
      15. That is what I thought. Floating bridges are the only practical way of crossing Lake Washington. Well except for flying cars, but I haven’t got mine yet, how about you?

      16. A deep-bored tunnel is another idea, and would be cheaper (and deeper) than a suspension bridge.

      17. I’ve seen that quote from the WSDOT website. It’s the same old can’t be done attitude. The “distruption of views” arguement is my favorite. I guess we should start an initiative to tear down the Space Needle because tall structures really make Seattle look bad. Floating highways are much better.

        It comes down to capital cost. Floating bridges are half the cost. They last half as long and since they aren’t built with a lower level deck capability like both of the Narrows bridges they are limited to half the capacity. The cost of the additional incurred debt is less than replacement costs down the road. The money’s never there to do it right but it’s always there to do it over.

      18. A tunnel under Lake Washington would have to be mighty deep and would still be incredibly expensive compared to a floating bridge.

        I guess one advantage is you could start the tunnel right at the foot of Lake Union and avoid the shuffle between 520 and the Mercer mess.

      19. What ever happened to the idea of a floating tunnel, submerged about 50′ under the surface? Heres a link to a Norwegian site that is a proponent of this technology.

      20. I think ten billion dollars probably happened to it. This stuff is expensive.

        Everybody thinks they have a magical solution.

      21. NSFT was established in 1998… At the time, an SFT crossing of Høgsfjord on the west coast of Norway looked likely to the first of a kind…

        No SFT has yet been built,

        While I think we should keep an open mind and encourage them to provide a proposal to me this looks like it would have all of the problems inherent with a floating bridge and be much harder to maintain. It would open up the lake but there would be no pedestrian/bike crossing. I can see an advantage in extreme climates (freezing/high wind/snow… kinda like Norway ;-) but not a lot to recommend it here.

  5. I seem to remember the vote by the ST board on whether to put ST2 on the ballot last Fall, came down to last minute maneuvering by the Director of WSDOT (can’t remember her name) to extract guarantees from ST about WSDOT’s I-90 bridge. IIRC, she was successful, ST made the guarantees on bridge maintenance, and she voted yes to get ST2 on the ballot. Given ST’s good faith then, and the outcome of the ballot measure, this wrangling now strikes me, a mere observer, as either stupid or bad faith by the State.

    1. It’s extremely bad faith by the state. I’ll be writing more about it, I’m trying to find a few choice bits of information first.

  6. I don’t understand why this debate was framed as 520 instead of I-90. In time, rail transit should be provided across both corridors. There is significant traffic between UW and destinations north of the ship canal and Bellevue/Redmond/Kirkland for whom a route across I-90 is not efficient.

    Given that a brand new bridge is being designed today – no construction has been started – light rail should be engineered into this bridge. There is no question that fossil fuels are going to be scarcer and the region should built less energy dependent transit.

    The question of how it links to downtown can even be answered later – but the bridge and alignment should be designed for light rail – even with I-90 as the main corridor to Bellevue.

    1. Excellent point, Carl. It is much cheaper to design it with the ultimate goal in mind than it is to fix it later. In fact, one of the best arguments for I-90 is that it was designed with high capacity transit in mind, and that was 30 years ago. As we are redesigning 520, the same care should be taken, even if light rail across 520 is 30 years out.

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