City putting $2.3 million lid on massive reservoir

Reservoir 4.
Reservoir 4 from above.

It may be the most expensive lid you’ve ever heard of. Concerns over cracks in the plastic cover of an 11 million gallon water reservoir spurred city public works officials to recommend replacing it with an aluminum or steel one.

The cost: $2.3 million.

It’s worth noting that this is a very big lid. Reservoir 4, as it is known, spans 1.25 acres. Only the nearby Union River reservoir, a billion gallons above the Casad Dam, holds more water in the city.

The past two lids on reservoir 4, both plastic ones, have “failed,” according to Bremerton civil engineer Bill Davis. The first cover, installed in 1981, had to be replaced in 2002. The second cover has been degrading for some time, Davis said. The city made the decision to forgo another “soft” cover that could cost around $500,000 and instead get a “hard” cover that should last 50 years, albeit at a higher price.

It may be an expensive fix, but this is drinking water we’re talking about. Exposure to the elements could lead to bacteria growth inside the reservoir, he said. Because the new cover will likely be made of aluminum, it will require columns to support the structure.

The end result is a permanent fix and is good for the utility and its users, Davis said.

“Our water supply will be more secure and it will improve water quality,” he said.

The Bremerton City Council approved a contract to design the project at its Nov. 4 meeting. Construction is slated to begin in June and wrap up in February 2017. The reservoir will have to be fully drained for the work.

How will the city forgo an 11 million gallon reservoir in a city which consumes around six millions every day? They’re still working on that, Davis said, but they’ve done it before on a previous project. It will likely involve using other water sources the city has, including its many wells.

The current work will be funded by the city’s ratepayers. A low-interest loan — one percent if the project is completed within two years — provided by the state’s Department of Health will spread out the cost.

UPDATE: Will it be recycled? 

Pat Watson had asked me whether the old lid could be recycled. So I asked Davis if the city was considering it.

He said the city reached out to Waste Management and found that the polypropylene material could be recycled there.

The contractor awarded to do the project will have the choice as to whether to recycle it, but Davis said the city would “encourage” the idea in its contract. As the project is designed, Davis said they’ll find out what other agencies have been doing with old polypropylene lids.

A "hard" cover lid on a reservoir in Laguna, California.
A “hard” cover lid on a reservoir in Laguna, California.

5 thoughts on “City putting $2.3 million lid on massive reservoir

  1. I’m not an engineer, and I’m not an accountant, but I can add.

    If the original plastic lid cost $500,000 and lasted from ’81 to ’02 then it cost $24k a year. If the new lid only lasted 14 years, it cost $35k per year. If you added the two together the cost per year was $29k? Considering the current lid hasn’t failed, I’d tend to lean towards the original $24k per year figure.

    But $2.3 million for a hard top divided by 50 years is $46k per year. It would need to last almost a 100 years just to break even.

    1. I did ask the question “why is it costing so much?” And the answer was that this one will improve water quality and last 50 years, though it costs more.

      1. How/how much will it improve water quality? What impact will that have on users? Will this have any net positive economic impact? Does having better water quality (meaning improving our quality from our current level to this new level) translate into fewer emergency room visits or less money on other services?

        The crux of my questions is: Is this a problem that needs solving?

        1. Hey Arthur,

          I talked with Davis some more after Robin raised the cost concerns too. Here’s what he said:

          “We performed a life cycle cost analysis and determined that an aluminum cover would be more cost-effective than ongoing replacement with soft covers. Our analysis indicated that over the 50 year life-span of a hard cover, soft cover replacement would cost approximately $2.8M, compared to $2.3M for the hard cover. Additionally, we are much more confident about the protection of our water supply with a hard cover compared to a soft cover that could be more easily compromised by degradation or vandalism. But even if the hard cover was more expensive, it has significant advantages, including minimal maintenance requirements, durability, longevity, and security. Also note that the new cover is being funded by a low interest (1%) 20-year loan.”

          1. Thanks Josh. Any chance those analysis are available to the public? Not trying to micromanage someone doing their job, nor am I an expert, but it would be an interesting insight into what factors they take under advisement and how they calculate overall costs.

            As Robin pointed out, on a straight cost per year of the physical purchase, the soft cover is definitely more cost effective, but I’m sure draining the reservoir every 15yrs costs significant amounts of money, as does the planning cycle, procurement, etc.

            I’m interested to see the total cost of ownership of the hard cover vs the soft cover. We have initial procurement costs of each, but only the TCO of the soft cover (unless the $2.3m for the hard cover includes the TCO).

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