Hatchet and sledge. No sparks no blowing up.
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That is a much thicker fuel oil tank, but I cut it out with the same method. 55 gallon ends are much easier.
I've cut dozens of 275 oil tanks with acetylene torch. Liquid doesn't burn. fuel oil isn't very volatile. Sparks get quenched by the liquid.
One night I was cutting one laid flat on forks. My son & his buddy asked me to move they wanted to get to that bay of the garage, I was blocking the door.
In moving, I sloshed a bit of fuel oil on the gravel driveway.
When I resumed cutting, the ground immediately burst into hot flame.
On another occasion I was removing a 20,000 gallon tank a friend in a bit of insanity had had hauled in. I'll guess it contained 25 gallons of oil & water in a mix. I didn't know what to do with the filthy mess. I decided to try to burn it off down to water. I sloshed some up on the wall of the tank, ignited it with an acetylene cutting torch. It took off in a roar! Horizontal flame shot from the end of the tank, before turning vertical! It sounded like a jet. People came to watch! I was sure I'd end up arrested for this, but police never came.