Water Towers

[TheNiche]

This is an abnormally technical question for HAIF, but I'm coming up short on answers without going to an engineering firm and actually having to explain the underlying purpose of the question, which I'm not willing to do at this time.

For a water tower capable of sustaining intense hurricane force winds and/or storm surge in a coastal area, how do the costs of construction typically break down? What are the big cost drivers? Is it capacity, height, construction technique, site work, mechanical, etc.? Anybody out there with answers?

[bachanon]

good luck with this question! thought i'd bump it up for ya, niche. it will be interesting to see if we have anyone with insight on this matter.

[Original Timmy Chan's]

This is an abnormally technical question for HAIF, but I'm coming up short on answers without going to an engineering firm and actually having to explain the underlying purpose of the question, which I'm not willing to do at this time.

For a water tower capable of sustaining intense hurricane force winds and/or storm surge in a coastal area, how do the costs of construction typically break down? What are the big cost drivers? Is it capacity, height, construction technique, site work, mechanical, etc.? Anybody out there with answers?

I'm not very knowledgeable in that area, but from what I do know, and you'll probably be surprised to learn this, usually about 1/2 the cost of a water plant is the cost of drilling the well.

I'm not certain on this, but I believe that elevated storage tanks are always designed for hurricane force winds.

An elevated storage tank costs more than a ground storage tank for the same amount of storage. An elevated tank requires more steel and is more difficult to maintain (paint).

Elevated:

Ground Storage Tank:

[TheNiche]

I'm not very knowledgeable in that area, but from what I do know, and you'll probably be surprised to learn this, usually about 1/2 the cost of a water plant is the cost of drilling the well.

I'm not certain on this, but I believe that elevated storage tanks are always designed for hurricane force winds.

An elevated storage tank costs more than a ground storage tank for the same amount of storage. An elevated tank requires more steel and is more difficult to maintain (paint).

Elevated:

Yes, I should've been clear that I'm talking about an elevated water tower. It does not necessarily have to be steel; slip-form concrete construction would be preferable to jump-form.

Examples to draw from (and note that the bulbous tower above would be unacceptable for my purposes):

[Original Timmy Chan's]

Well, Niche, you get nothing more from me. That was the extent of my knowledge.

[jgs1419]

This information may be outdated (15 years or so?) but it might provide some guidance. You have identified four tank styles in your photos:

A legged tank: So called because it has.........legs. Very clever. This style of tank dates back to the railroad days of the late 1800s with some of the original riveted tanks still in service. Cheapest to build; most expensive to maintain due to the extensive mechanical connections that hold the cross bars together, myriad of welded connections, etc. Back in the day, a large (1MM gallon) legged tank might cost $0.65/gallon for the foundation, tank and painting.

Fluted Column Tank: That's the one with the large steel pillar in the center and tank on top. One advantage that municipalities sometimes like is that it has a place to store stuff in the base of the column. Disadvantage, sometimes these things look like a behemoth on the horizon. A 1MM gallon tank back in the day might cost $.85/gallon but the paint/maintenance were alot better due to the limited connections. Paint area is still quite large so repaints cost money but less than a legged tank.

Waterspheroid: The golf ball on a tee tank. Minimal weld connections, smooth surfaces, etc. minimize paint area and make long term painting costs lower due to minimal connections. More expensive to fabricate/construct but competitive with fluted tanks in large capacities. Probably $.90/gallon but lower paint costs long term due to lower surface area.

Composite Tank: Concrete shaft and steel tank. Some think they are ugly. I've seen some decent ones, some ugly ones. Typically in the same cost ball park as a fluted tank but routinely cheaper in the south where labor costs are low (we have a lot of them in Houston). Steel is typically cheaper up north but not always so. Selling point was always you don't have to paint the concrete shaft thus having lower capital cost and lower maintenance but most of the decent ones I've seen they paint the shaft to eliminate the pour lines in concrete.

There are gillions of these things in coastal areas around the country. From what I remember, designing for 120mph wind speed using ASCE-7 is relatively common. High seismic loads can be costly for the foundation and for the legged tanks.

Steel costs are probably 5 times what they were 15 years ago so my cost data is probably out of whack. Cost drivers are capacity (relatively linear unless you go below 300M gallons of capacity), height (80' to 100' to the top water line is common; taller costs more especially in wind/seismic areas). Beyond that, steel and fabrication will be well over 60% of the total cost so construction technique and methodology don't have a huge impact. It's alot of welding and alot of painting - pretty straight forward.

Hope that helps.