underground storage tank

If you can dig out a small part, I think you can try an ultrasound.. it might work.. if the reading comes back and says it .5" thick or less, then it might be double walled, if it can get a reading because the thickness exceeds the capability it could be reading the fluid inside... single walled..

(thinking out loud) that would only work if you knew you were below the liquid level when you did the test....

If there is a way to uncover the original architectural drawings and the call outs for equipment, you may find the manufacturer specified and the model and specs.

Failing that, a call to the local code enforcement agency will perhaps tell you what local ordinances there were in place at the time the building plans were approved by the municipality. You'll need to know the dates during which the project evolved. If it's a very old building, say over 40 years, it's not likely a double wall ordinance was in place. If after digging some all you can see on the tank is the name plate with model and manufacturer clearly visible, then it's a cinch to answer the question. That's assuming, of course, that the guys who made it are still around!

Good Luck!

L. J.

PJL,

Some additional information may help in determining the answer to your inquiry...

How large a tank do you have ?

Is it equipped with a manway ?

What kind of "oil" do you store in it ?

Any idea how old the tank is ?

Where geographically is the tank ? (i.e., what country/state/city)

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Just my $0.02...

Listen with a stethoscope while you tap it with a hammer.

You may be able to detect an "echo" from the second surface if it is double walled while the single wall would give a simple sound. You can "calibrate" by checking against the sound from a manhole casing or cover where you know it will be single walled.

At best this will be indicative only, but it can help you decide if you need to check further.

If you think it may be double walled, an ultrasound with an experienced operator will be able to sort out the question. A double wall will give an echo on the trace and quite clearly show the interface.

It should be able to be done on the upper part where there is no oil (in the ullage space), and this should be accessible through a manhole, making excavation unnecessary.

Good luck

When double wall tanks were mandated, interstitial leak monitoring equipment was also made a requirement in most jurisdictions. Whether you have or do not have leak monitoring connected to the tank will give you a good clue.

The manufacturer's plate should be accessible from the manhole. This will have the construction details on it.

Cheers,

Steamer

If it is a double-walled tank, the interstital space will have a separate vent pipe. If you have only one vent pipe, it is probably a single-walled tank. I've never seen them both vented by one pipe. All UST's in the US were mandated to be replaced or upgraded by 1998, so you should be able to tell something from the age as well, if you know it.

mostely under ground tanks is made of a fiber glass

depending the capacity of the tank , and thickness

it can single, or double wall .most dangurous chemicals

will store in double wall. other wiseit is single wall.

cherian

I used to work as a welder of tanks, food grade and underground fuel storage tanks.

Underground tanks were indeed double walled and in our facility we would draw a vacuum between the inner wall and outer double wall. On either end at the top of the 50,000L tanks there were fittings with a vacuum gauge on them. If the tank ever lost vacuum it was pulled from service for inspection.

If it is a double walled tank there is a good chance you will find such a vacuum guage on it.

Also on these tanks there were re-pads placed around all fittings as the outer skins were only 1/8" and I do believe the inners were 3/16" thick. The fittings were welded to the primary thick walled tank and the re-pads would seal the outer skin.