Underground tank regulations only apply to, um, underground tanks. We had a 100 gallon above ground tank at an old house I lived in once, which wouldn't be affected by UST regulations (of course maybe there were other applicable regulations), that was used for fueling farm equipment. And of course it's very common to have home heating oil tanks of 500 gallons or more. You can run a diesel engine on heating oil if you have to.

underground is highly regulated, but many people have 100 gallon tanks above ground. My grandfather had two, my father stores 50gal in gas and 50gal Diesel. If you have enough property buy an old farm tractor and a brush hog to "mow" your land and then fill a 50gallon drum, if you truly farm you can get a farm discount (just don't use any on public roads) or some of the small stations will still give a bulk discount. They are much less picky about above ground though it seems to me gas leaking from either would cause just the same mess, however you could have a leaky underground tank and never notice until its empty where a leaky above ground tank you will notice the smell and puddle on the floor/ground.

I think the reason they get more upset about below ground is that it's a lot less obvious if it leaks. You can pretty much tell right away if above ground is leaking- you see a wet spot on the ground.

nothing really to add to the discussion but im curious how long it would take to fill said 100 or 500 gal tank of gal, oil etc.

We have two diesel tanks, an oil tank for heat in our shop, and one gas because we do commercial construction. We used to have below ground tanks with pumps, but they have become difficult to have with all the enviromental stuff, so we took them out and now use above ground. In fact we are waiting on an ok from the town to build on land that was contaminated by an underground diesel tank. Best bet now is to go above ground if you have the room. For the average person who doesn't plan on using a lot frequently maybe a steel drum with a pump might be a better solution? Fill it once with gas cans and then make sure you keep it topped off. A drum is a bit easier to move around when needed then a big tank.

Well, since ki4buc mentioned burying a tank, I thought the UST regulations would be relevant. Of course, if the tank is above-ground, it might be more susceptible to storm damage or pilfering, but (as the posters above note) it would be easier to spot any leaks.

Not real long, I went with my father a few times to fill his 50gal, its just liek filling a truck with a big tank, some full size trucks can be bought with dual tanks that hold 25 gals each so its just like filling one of those.
Grandfather would have a big tanker truck drive down to the farm and fill his, same truck that fills the gas stations IIRC so it has a bigger hose and bigger pump would fill real quick.

A few years ago I used to work for a large supermarket chain, who also sold thier own brand Gas in pumps next to thier stores.
When a gas truck crashed or rolled, the concern wasn't for the cost of the gas, it was for the cost of the cleanup operation. If the gasoline ended up in a farmers field than then entered the water table the cost rose dramatically. Compensation doesn't come cheap.
I have no knowledge of US law, but the cost of a leak will probably outweigh the benefits of storing such large quantities.
Just my 2 cents worth