Why 4-year-old West Seattle Reservoir needs a multimillion-dollar retrofit – and Myrtle Reservoir is expected to, too

(SPU photo inside West Seattle Reservoir in May 2010, not long before it was filled)
By Tracy Record
West Seattle Blog editor

Only four years after it went into service, the underground West Seattle Reservoir in Highland Park needs a $7.6 million earthquake-resistance retrofit.

Work will start this summer, while the city and its consultants determine the scope of retrofitting that is also expected for our area’s other underground water facility, Myrtle Reservoir in Gatewood, as well as for two others in the city, Beacon and Maple Leaf.

We talked today with Seattle Public Utilities and its consultants about the problem, the solution, and the work ahead.

This was foreshadowed a year and a half ago; we made note of it here in November 2012, following up after The Seattle Times (WSB partner) broke the news that the reservoirs’ designer, MWH, had told the city about what SPU calls “possible seismic deficiencies in their work.” SPU subsequently announced that testing would be done to find out about those potential deficiencies and what would be needed to remedy them.

They didn’t expect the testing would take as long as it did. West Seattle Reservoir is the first one for which a seismic review has been finished and a retrofit plan laid out.

We found out about it when a public notice seeking bids on the West Seattle Reservoir work appeared online last week. Our subsequent inquiries with SPU led up to today, when we and a Times journalist met at the Municipal Tower downtown with SPU’s supervising civil engineer Aziz Alfi and media liaison Andy Ryan as well as two managers from the consulting firm CH2M Hill, which has led the seismic review, Wally Bennett and John Spencer.

First thing you should know is: SPU says the reservoirs “are in no danger of catastrophic failure,” even without the retrofits. But the testing showed that a massive quake – one that would make the 2001 Nisqually quake look like a gentle shake – would likely render them unusable, and that is not acceptable to the utility.

It was stressed that none of the reservoirs will have to be dug back open for these retrofits – the work will be done inside, with crews and equipment accessing through existing maintenance hatches. The work will take the reservoirs out of service for months – not concurrently (the timeline is explained later) – but that won’t lead to any water restrictions or shortages; SPU says it will simply route water service other ways.

Spencer explained the backstory: Once the designer (MHW) disclosed the reservoirs were not likely able to meet seismic expectations, the discussion, as well as a review by outside experts, led to a plan for 3-D modeling.

This led to what was in essence the invention of a type of computer analysis that so far has been completed only on West Seattle Reservoir, with the other three to follow. The central square below correspond with the square outlined in red in the aerial photo above.

The computer modeling looked at the reservoir structure piece by piece (see the squares in the renderings above and below) and analyzed how each of those pieces would react in an earthquake of the type that might happen only every 2,500 years.

We’re told there is no magnitude that can be assigned to that hypothetical quake – just, much stronger than Nisqually, and of a different type. Each reservoir was analyzed in the prism of the type of quake most likely to be the strongest potential quake in its geographic area; for the West Seattle Reservoir, that’s a Seattle Fault quake.

Other firms were brought in for the computer analysis, including SC Solutions of Sunnyvale, California, which has experience in “high-end finite-element computer models, and specific experience with buried structures.” The analysis was so complicated, using “supercomputer”-type functionality, that just “one run” resulted in a terabyte of data.

What they had to test, explained Spencer, was whether a catastrophic earthquake would still leave the 30-million-gallon West Seattle Reservoir functional – would it hold water so that drinking and fire-fighting water would still come from it? The initial test runs revealed: No, it wouldn’t. The consultants say it would not burst “like a dam” – but it wouldn’t hold its water, so to speak. It would drain out, mostly into the earth, within hours/days.

Once they got the problem sorted out, they started testing possible solutions. A conclusion: This catastrophic quake would lead to the West Seattle Reservoir’s floor slipping – almost an inch, seconds into the quake, Bennett said – and its north wall cracking. So a “joint” in the reservoir’s floor has to be covered in an additional 8-inch-thick slab of concrete to make sure it doesn’t slip much if this kind of quake happens, since the testing determined that retrofit would help the structure “gain a lot more resistance to movement,” resulting in fewer stresses to other parts of the reservoir. Two other areas of the floor will get an added slab, too. And the north wall will be covered in a polyurea liner that will keep water from getting out even in the event of major cracking of the wall.

So this work is what has gone out to bid, with bids due to be opened on July 2nd, and work to begin by fall, lasting about five months. It’s not affecting the park-building project on the West Seattle Reservoir lid, SPU says.

Meantime, the Maple Leaf reservoir is being analyzed now, and whatever retrofit work it needs is expected to be done next year. Myrtle Reservoir in Gatewood – by far the smallest undergrounded reservoir, at 5 million gallons – is also expected to have a 2015 start for whatever retrofitting is needed, possibly by the end of next year. Beacon Hill Reservoir would follow in 2016.

The full price tag could be up to $30 million for all four reservoirs, according to SPU, which says it has been “working collaboratively with the reservoirs’ designer to recover the costs of the repairs.”

You might recall another reservoir problem first reported here back in 2009 – waterproofing leaks at Myrtle (where the undergrounding was completed in 2008) and Beacon Reservoirs. That wasn’t related to this, but Ryan reiterated today that the costs were covered by the contractor, and that cost recovery is being pursued just as intensely in this case. Alfi says MHW already has made “some payments.” SPU says that “to date, the overall cost of building and repairing the four reservoirs is about $133.5 million – $15.5 million under the original budget.”

The retrofitting would not prevent all reservoir damage in case of a catastrophic quake, but it would leave the reservoir in “repairable” condition, not losing a lot of water, because, as Bennett said, “our expectation is that the structure and the soil (would) move together.”

We asked how much of the technology and methodology would be reusable for the studies of Myrtle, Beacon, and Maple Leaf reservoirs. Each is unique, the consultants explained; each will behave differently, and each faces a different kind of potential quake threat. But, Spencer said, “We have learned a lot in the course of doing this work, so we’ll be able to (move) more quickly on each one of (the remaining three).”

The order chosen for studies and repairs is in part because of “water supply considerations,” Alfi said. While the retrofitting work is under way, the reservoir will have to be drained and kept out of the system. That requires planning and rerouting comparable to “traffic controllers,” he added. “Instead of detouring cars, we’re detouring water.” They’re also coordinating the water “detours” with other SPU projects.

But all the work will be done inside the reservoir, said Bennett. “No new holes in the surface – no excavation. It will go inside through three existing hatches. The contractor will mobilize the site so you’ll see trailers and typical construction (crews/equipment).”

The mobilization for West Seattle Reservoir is expected to start in August; it would be completely empty from September through January. The draining, said Alfi, will mostly happen through regular usage, with the water level allowed to continue falling as people use the water, and whatever finally remains at the end would be routed to some other system. (If the reservoir ever had to have its contents drained to the storm-drain system, it feeds into the Duwamish River, we were told.)

At that same time, the contractor for Seattle Parks is expected to be doing landscaping atop the reservoir.

So why did the safety analysis take so much longer than first anticipated? The piece-by-piece review was something that had never been done before, for one, but a breakthrough finally happened when a new staff member at SC Solutions applied a model used in analyzing car crashes. And it might not have been so complex if not for the fact the city had four reservoirs with potential seismic deficiencies; if it had only been one, the project team said, they might have taken a different approach.

Will the lessons learned here be applicable to any future SPU projects? Ryan noted that Volunteer and Roosevelt reservoirs remain offline as SPU continues to evaluate whether the system is OK without them ever going back into service, and that evaluation has another year or so remaining, so currently there is no anticipation of additional undergrounding.

Ryan says the City Council has been updated on all this, particularly the Public Utilities and Neighborhoods Committee. A Council decision in 2004 led to the undergrounding of six reservoirs including the four involved in this review, with health and security concerns in mind.

29 Replies to "Why 4-year-old West Seattle Reservoir needs a multimillion-dollar retrofit - and Myrtle Reservoir is expected to, too"

  • Ray June 18, 2014 (11:58 pm)

    Construction work has been underway for over a week now.

    They fenced off the entire reservoir (the big green area where everyone would let there dogs run free right next to the dog park).

    As of this week they have already laid down a lot of gravel drive paths for the heavy vehicles and removed a lot of top soil/grass.

    Seems strange this is just now a story in the Times when it has been underway almost two weeks.

    • WSB June 19, 2014 (12:10 am)

      No, this work is not under way. As I reported in the story, the bids have not even been received, let alone opened – the request for bids just went out last week (which is why we contacted SPU – we and the Times were the only organizations working on this and that’s why we were the only ones interviewing the four people today). Parks is continuing to work at the site – the “big grassy area” is part of the park project that’s been in the works ever since the reservoir was covered. – TR

  • clark5080 June 19, 2014 (12:11 am)

    So they didn’t consider this issue when they were designing the cover’s a while back? Seems like a major mistake now we the taxpayers pay again for shoddy design work.

  • dsa June 19, 2014 (1:06 am)

    Really? It’s interesting that the Alaskan Way tunnel people have had a casual take on what happens to underground structures during earthquakes.

  • Ray June 19, 2014 (1:09 am)

    Then I stand corrected as to the purpose of the current construction. There is no signage anywhere around the site indicating what is going on and the significant turf removal and temporary roadwork that is in place indicates a significant project (as does the numerous pieces of heavy equipment).

    • WSB June 19, 2014 (1:16 am)

      Here’s more info on what the Parks project entails. It has been so long in the works now, I’ve pretty much forgotten myself … we covered it extensively in the early stages. The coordination with SDOT regarding road components (mentioned on this page) caused some delays. http://www.seattle.gov/parks/projects/west_seattle_reservoir (The page does have confusing time info … the spring/May 2014 mention at top is correct, the lower dates about 2013 etc. are not.)

  • Mike June 19, 2014 (6:15 am)

    dsa, there’s a major difference in how a box with pillars can withstand a quake vs. a cylinder. You’re safer in a cylindrical tunnel during a quake than any viaduct ever built. The tunnel project had many many cases studied to consider earthquakes and the potential damage, especially since it’ll be near water.

  • anonyme June 19, 2014 (6:31 am)

    The taxpayers of Seattle have repeatedly been on placed on the hook for millions of dollars due to negligence by City agencies. There has got to be a way to make government accountable. Many of us are squeezing pennies to survive while these bozos squander our hard-earned cash. Despicable. I’m so sick of hearing these stories.

  • miws June 19, 2014 (7:52 am)

    I may have misinterpreted what was in the article regarding the costs of this retrofit, but isn’t SPU negotiating this with the designer, so that the cost in borne by the designer?


    That was my concern as well; tax/ratepayers bearing the cost for what appears to be negligence by a private company. If my understanding is correct, I would only hope that the designer indeed pays ALL related costs, including any that might be incurred in these negotiations.


    Otherwise, I wonder if the water that normally runs through the areas of the “detours”, will complain about the added “traffic”? ;-)



    • WSB June 19, 2014 (9:06 am)

      Sorry, I was responding to the previous comments and got interrupted. The various parties are “collaborating” on the financial discussion, though whether that will result in litigation at any point, too soon to say. The designer also was one of the parties that covered about two-thirds of the costs of the waterproofing problem in 2009 (mentioned here). The consultants/SPU managers in the conversation yesterday stressed that what was done was seismically sound – but not up to this super-mega-quake standard – I guess maybe as if you delivered a car that ran but didn’t have all the safety features that new cars now have (rear-view camera, etc.) – simplifying it wildly. And since even with the city obviously fronting the cost of the retrofit, it is all still within the original budget because the project was under budget, SPU says, so this is NOT resulting in rate hikes. As always, I’ll watch comments here because there may be a followup question I didn’t ask … the four people quoted stayed until the Times writer and I ran out of questions but recognized there might be followups. – TR

  • CanDo June 19, 2014 (8:36 am)

    Yup… cause when they were built 4 years ago, no one thought there could be earthquakes here… sigh. On and on it goes.

  • blockedpunt June 19, 2014 (8:40 am)

    Well before we go hanging the government out to dry, it sounds like the design errors came from the A-E firm that was retained to design the reservoir in the first place. True, the gov should have been performing quality assurance on the product they were getting, but professional responsibility rests with the designers. The firm should pay to fix it. I would imagine some engineers are sweating bullets about their licenses…

  • Joe Szilagyi June 19, 2014 (9:53 am)

    Have we asked SPU and the City why the original design didn’t include this work?

    • WSB June 19, 2014 (10:04 am)

      Sorry if that’s not clear. The designer delivered the design and said it was up to code. They later discovered that they’d made a mistake – as originally reported in 2012 (linked above but here’s the link again), their calculations were based on above-ground reservoirs, not underground reservoirs – and brought it to the city’s attention, SPU says, rather than just sit and hope nobody would notice. The type of work done to test and see if indeed there would be a problem was basically invented from almost-scratch – we were provided with lots of geeky tech detail (this story already was long enough) about how they created the type of testing that resulted in the recommended retrofit. (After testing the reservoir in a piece-by-piece 3D computer model, they then had to run through possible solutions to see what would achieve the desired results.) – TR

  • No, No, No. June 19, 2014 (10:18 am)

    What utter incompetence on behalf of the designer. Big difference between above ground and underground. Once again, we tax payers get stuck with the city’s (yes, the city should have caught this egregious blunder) mistake. Must be the same people overseeing the digging of the 99 tunnel. Unreal how poorly this city manages construction.

  • trickycoolj June 19, 2014 (10:55 am)

    It really worries me that when selecting contractors for major projects we’re spending more time making sure to award the projects to companies owned by specific demographics rather than capability and experience at actually doing the work. How many more recent projects are going to be plagued by rework?

  • Gatewooder June 19, 2014 (11:37 am)

    I suppose that the real news would be that the work had been done correctly. What is it with public procurement and engineering in this region? The Spokane Street viaduct is having to get patched after being open for less than two years, Bertha is stuck on the waterfront, and Sound Transit is still trying to finish a light rail system almost twenty years after being approved by voters.

  • wetone June 19, 2014 (11:56 am)

    Same old story, just add it to the list of projects in this city and state that for some reason can’t get built right the first time. Whether it’s built under budget or not is no excuse for this oversight except showing the incompetency of our city and state engineering groups and officials for not doing their proper job and homework once again. Wow if this is really true [their calculations were based on above-ground reservoirs, not underground reservoirs – and brought it to the city’s attention, SPU says] no one caught that before build really ? Curious to how much $$ they have spent testing, reviewing and planning the fix, still under budget ? Just goes to show you how good all the old school engineers were, no computers and they could build it right the first time and it would last. Once again tax payers will pay one way or another and the people involved will get a pay raise.

    • WSB June 19, 2014 (12:10 pm)

      The $7.3 million includes the cost of reviewing, planning, etc. The bid request (linked in the story) estimates the actual work will cost just under half that sum.

  • Rick June 19, 2014 (12:08 pm)

    Nothing more than business as usual. And nothing less. I used to like the saying “Ignorance is bliss”. In my later years I’ve added “Because the more I know, the more pissed off I get”.

  • BT June 19, 2014 (2:07 pm)

    To be sure, a City reviewer should have caught that the below ground analysis would be different than above ground. But I disagree with wetone’s comment about how good all the old school engineers are, we haven’t experienced the kind of subduction zone quake that this fix is addressing so we don’t know yet (outside of computer models) if the old designs will stand up or not – the Nisqually showed that some “old school designs” (ie Pioneer Square) didn’t stand up very well, with some classic old structures(Phoenix Underground, Seattle Chocolate) damaged beyond repair, and we all know the deal with the viaduct.

  • WestSeattlite June 19, 2014 (2:39 pm)

    The article does not make clear (at least to me)whether this was a design specification in the original request for proposal. THAT is the critical piece which will determine who is on the hook for correction. If SPU did not properly specify the performance required, which, by all the careful wording from them, I suspect is the case, then once more taxpayers are responsible for poor project management by our government agencies. I see that “cost recovery is being pursued just as intensely in this case” but if they got what they asked for, there isn’t much recourse.

  • me June 19, 2014 (4:14 pm)

    People are so quick to jump on the government agency bashing bandwagon. The private consultant botched this. The city hires consultants when they do not have capacity or expertise. When they do, they transfer the risk to the private firm. Of course there are gray areas and many lawyers involved, but city representatives are doing everything they can to place financial burden where it belongs.

  • dsa June 19, 2014 (4:31 pm)

    “…We’re told there is no magnitude that can be assigned to that hypothetical quake – just, much stronger than Nisqually, and of a different type. …”
    That statement seems outrageous to me. I think they need a design standard.

  • TBone June 19, 2014 (8:13 pm)

    As an architect, I find this thread fascinating for a number of reasons. First is that earthquakes are all different. Much depends on the frequency of the wave, the depth of it, the soils, rather than the magnitude alone. You could have one that is very low frequency (think of a low bass note) and rolling with a high magnitude that causes much less damage then one that is a high frequency (treble note) wave with less magnitude.

    In terms of design and criteria; I would be astounded if no one reviewed the plans and approved them. That said, it doesn’t matter. The city, the state, whoever reviews drawings and approves them takes no liability whatsoever for anything approved by them. They make that clear on every set of drawings and permit they issue. Ultimately, it is the architect or engineer who bears responsibility for ensuring that the design is in accordance with the code.

    It is a pretty stunning error, nonetheless…

  • Rick June 19, 2014 (9:19 pm)

    Yes, stunning.

  • EasierToRead June 19, 2014 (9:38 pm)

    >>and Myrtle Reservoir is expected to, too<>West Seattle Reservoir is the first one for which…<<

    West Seattle Reservoir is the first for which…


  • Born on Alki June 20, 2014 (10:18 am)

    Yet another example of some stunning project management by City of Seattle “experts”. How could this have possibly been overlooked? Heads should roll but ultimately the citizens will pay for this blunder too.

  • Robert June 23, 2014 (7:21 am)

    I kind of wonder ,we have one of the best engineering schools in the western world here in seattle with connections to many other schools of higher learning with the brightest minds in the engineering world why don’t they get to review the plans before we spend so much of the taxpayers money on turkey-designed junk??????? it would be a chance for the best and brightest to show their mettle,of corse that would show the good-ole boys up….

Sorry, comment time is over.