Why are some tank sweeps better than others?

aka, why metal detectors are not worth the money for tank sweeps.

You are looking at about $8000.00 worth of metal detectors and yes many people will charge you $200.00 to $250.00 to use one to scan for an oil tank.  

Well metal detectors cost between $800 and $1,000.00 so they can’t charge too much because you don't get much.  Buy a metal detector and go to the beach, you will surely find some metal, coins, bottle caps, maybe a lost ring or a watch, fishing hook, etc, because that is what is buried in the sand.  You should not expect to find much else because its the beach and a metal detector makes perfect sense.

Now go to a residential or commercial property and look for a buried tank and you will find buried utilities, pipes, metal containing soil, buried debris, rebar and wire mesh in concrete and of course metal signatures of aboveground metal features such as the house, fences, grills, parked cars, etc.   in short the metal detector will beep a lot. 

Common scenario, we get hired to remove a tank that was found during a home inspection or metal detour scan.   We apply for and obtain permits, (takes a couple weeks).  Buyers and seller are present on day or removal, all to often we find no tank.   Just buried metallic geology (soil) or debris.

That is soil that has metal in it. Note the color differential of the soil?  Well the darker soils have iron sand in them, which confused the metal detector.

This tank never would have been found by a metal detector as it is not metal, but it was made in New Jersey.

Metal detector missed this tank because it was too close to the ac unit, which is metal and gave a misleading metal signature.

This metal detector scan we really confident that a tank was there, turns out it was just soil with a magnetic signature.

That is buried debris. Round piece of metal, why was it buried, no idea, but it was flat so a GPR would have noted a no round object so likely no tank.

Not sure what this is

Ok you get the point, metal detectors detect metal regardless of what the metal is. Commercial sites have geophysical investigations performed which at a minimum is Ground Penetrating radar.

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