Can I convert a large fuel storage tank to an irrigation tank?

I hope someone can give me some really useful information on this.

I was given an approximately 5000 gallon steel fuel tank that has apparently been "professionally" cleaned. It has also been sitting for some time, and has had a fair amount of water flow through it... when I went to pick it up, it was accidentally rolled into a pond and had to be fished out, and where it sits upright on my farm it has been filling with water through the top with a hose from my well for several months, and draining out one of the holes in the side.

Nevertheless, when I stick my head in the access hole on the side, I can still smell a faint odour of some sort of fuel... very faint.

My great desire would be to use this tank for an irrigation cistern... fill it with water in the wet season and irrigate with it in the dry season when my well isn't producing much.

Does anyone know if the metal tank absorbs the fuel, and if so, how could I go about fixing that?

Any suggestions for making this tank safe for irrigation water?

Hey Austin- my reply is my opinion, it is based in 14 years experience working in the oil and gas industry. I would strongly discourage you from using this tank for irrigation purposes. Even if you identify the type of fuel previously stored in the tank that is just the tip of iceberg of potential issues. Most industry tanks and vessels are treated in their service life with an array of highly toxic chemicals in addition to the product stored. Biocide is a particularly nasty one, I won't get in to it too deep, but consider the the Latin root is roughly transliterated as 'death to life'. Biocide is used because a surprising amount of unwanted growth can occur in process systems. Fuel stabilizers, conditioners and other additives add another realm of chemical possibilities. An unexpectedly deadly amount of hydrogen sulfide (H2S) can be entrapped within internal sidewall corrosion via anaerobic digestion that lies latent until disturbed. For perspective the OSHA allowed exposure to a worker is only 10 parts per million weighted over an 8 hour shift. This stuff is so insidious that crews I worked with would stop work if any amount of H2S was detected with our meters. H2S can be smelled (similar to rotten eggs) at low levels, higher levels kill the sense of smell and people die because they think they can always smell it. It takes metering to be sure. This is a large tank, please don't ever allow anyone to go inside or put their face in it or allow pets/animals to access just in case.

I'm not trying to be a downer in this situation, you have an otherwise substantial piece of infrastructure that I personally would not feel comfortable using for anything other than fuel storage, but I would never need that much fuel. If it could safely be stripped to bare shiny 'see your reflection in it' metal via mechanical means or sandblasting internally then I may be in the conversation to think otherwise. But that would be another effort fraught with expensive controls to ensure it was done safely, properly and ethically. In the current state I would consider at most using it to contain a bladder for my irrigation water that kept the water from contacting the internal surface of the tank and set it up that any bladder failure would leak out a low point so I would have indication that it was leaking. Or sell it to someone who needed a huge fuel storage tank.

-Josh

Austin, I'd apply the principles of permaculture. Sounds like before doing something, you observed the tank and know it's recent history. Good start!

Then we'd need to think about the energy that could be saved or lost by not using or using it (It took a LOT of energy to make a flat steel plate!).

Then, what's best for reversing the destruction of our planet? (Such as: The only real way to dispose of nuclear waste is to divide it into grains of uranium & plutonium and add them to the overburden of the mined mountains they came from. To form new mountains with flowers and other natural plants and grasses on their skins!).

I think the best use of a steel tank (Caution!!! Could explode!!!*) is to safely cut it into patches for used farm equipment (mower decks etc.)
* Milwaukee makes (and others) makes a 'skill saw' that will cut metal like plywood. If in doubt about the chance of a explosion for existing fumes fill with water to top and tip tank slightly to create a very small air pocket.

Then back to the first principle. Observed!

Jon