Water Tower Inspection

[dbill74]

In the very near future I am going to be going to a unique location with limited access to survey a job site. While at this location I have been asked to look at a secondary project. This secondary project is a water tower that was taken out of service almost a decade ago due to "seismic damage". The client now wants to put this water tower back in service.

My job while on site is to visually inspect the tower and provide a preliminary assessment and recommend the next course of action. Ideally, a strctural engineer would be better qualified to do this, but we do not have one available. (Without question, structural engineers will have to be engaged at some point.)

What I am asking from the community at this point are things to be looking for (beyond the obvious buckled beams/columns) that would indicate a compromise to the integrity of the water tower or other reason it may have been labeled "seismic damage" and taken out of service. Pictures or other examples would be great.

Thanks.

 

[MotorCity]

What type of construction is it? I would like to see some sort of documentation as to why it was taken out of service, perhaps field records or inspection report. "Seismic damage" is not very descriptive. Connections usually fail before the structural members, so I would pay close attention to bolts and welds. Look for corrosion. Seems like a good application for inspection using a drone or Go-Pro.

 

[SlideRuleEra]

Agree with MotorCity, look at and adjacent to connections - bolts and welds. You are looking for cracks or distortion in those areas. If a drone is not available, take a pair of binoculars with you, since I assume you will not be climbing the tank... at least not all over it.

Pay special attention to visible concrete foundations including anchor bolts. Damage to either the concrete or the bolts is probably easily observed... if you look for it.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[ATSE]

Water tank is a fairly broad category.
Steel? Welded or bolted?
Elevated?
Concrete ring foundation (type 1)? Self anchoring?
Cast-in-place concrete or prestressed concrete?
These different tanks have very different limit states and failure modes

 

[nackra]

https://www.awwa.org/store/productdetail.aspx?productid=29319

another reference to consider

 

[dbill74]

Thanks for the quick responses. You have some good questions, unfortunately I don't have much in the way of answers; yes I'm going into this kind of blind, yes I wish I had more information.

Managed to find what I believe is the tank on google earth and it appears to be ground mounted (so yea "tower" is looking to be wrong terminaology). I'm told the capacity is 200,000 gallons. I am assuming it is steel. Purpose is/was fire protection water for adjacent air terminal.

A drone is not going to be permitted.

I agree ther term "seismic damage" is broad, again that is what I was told. One of my objectives is to determine the nature of the "seismic damage".

I would like to see some sort of documentation as to why it was taken out of service, perhaps field records or inspection report.

Me too.

 

[WARose]

In addition to what the others have said.....it may also be worthwhile to get some data on this event itself. (I.e. from the USGS.) Having an idea as to the magnitude of the load may help you (or the structural engineer you hire) possibly locate other damage that should have been induced.

 

[LittleInch]

Take a spirit level and check horizontal or vertical misalignment.

Was there any chance of liquefaction and settlement of the tower? Difficult to see, but any evidence of voids under any concrete slabs or supports



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[dbill74]

I'll be sure to pack a level, thaks LittleInch.
As for luiqifaction, I don't know, haven't seen it yet. I won't rule it out, what should I look for that would be a tell-tale sign of liquifaction?
Leaning Tower of Pisa?

 

[SlideRuleEra]

To get a general idea of tank failure modes, may be helpful to review the 102 page (free) book "A Study of the Performance of Petroleum Storage Tanks During Earthquakes, 1933 - 1995". It was published by the U. S. National Institute of Standards and Technology (NIST).

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[chicopee]

In addition to the suggestions mentioned above, an internal inspection of the tank is in order.

 

[dbill74]

SlideRuleEra,
That looks like an interesting read, thanks.

chicopee,
Good idea, I hope I can get a good view of the insides, we will see.

 

[dik]

Any drawings available? I've encountered watertanks that were riveted and used wrought iron...

Dik

 

[JStephen]

Does the tank have to meet current seismic requirements when work is completed? (may be impractical) Or requirements in place at time of construction?
Is the tank per NFPA 22? Is it an FM tank?
Look for damaged roof plates, top angle, or upper shell due to sloshing, if roof plates are damaged, looking for damaged structure inside.
Look for stretched/elongated anchor bolts or damaged shell around anchor bolt areas.
Look for "elephant's food bulge" around the tank.
Look for damaged piping or nozzles due to tank movement.
Check for general corrosion damage.
Prior to doing anything on any old tank, check for lead based paint; that will affect the economics considerably.

 

[JoelTXCive]

If possible. Please post any good photos from your inspection. We are all interested!

 

[dbill74]

Thanks for all the tips and questions guys. I will be heading out tomorrow. I'll check back in when I'm back and let you know what I find.

 

[dbill74]

Alright, been there and seen the tank. And it is a tank not a tower.
The attached PDF includes a portion of my final field report with photos and observations.
Thanks for all the responses and input.

 

[LittleInch]

Not much extremal signs of seismic damage then? Pity you couldn't see into the tank via the manway.

What next?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[dbill74]

I agree, no obvious signs of seismic damage on the outside. Foudation looked to be in excellent condition, a few hair line cracks.

Given the location of a lot of the rust spots being at joints, the roof/wall interface and the base; I'm not sure I would trust that it could be adequately patched. There's a bunch of spots. If anyone thinks differently, please speak up.

Then there's the vegetation growing up under the tank where it meets the foundation.

Finally there's teh gulley on the north side where a drain is located. No signs of recent erosion; I'm thinking this gulley is more a result of a leak at one point that was patched. Would explain the buildup under the drain and the metal frame holding the drain pipe (no picture of the frame).

Erring on the conservative side, my recommendation to the powers that be is to replace it.