Been there, done that...
1. If there was gas, diesel or heating oil in it before, forget it! You will never get them clean enough to get the odor out without spending a fortune. Believe me, you can steam clean them thoroughly with the toughest detergents and still suffer.
2. Check your ground water level, if it is below the tank you are burying, OK... if not, the tank will float right up out of the ground and you will have a mess, even if there is 3-4 feet of dirt on top. If you have drainage possibilities, rely only on gravity - pumps can and will fail.
3. Steel tanks will rust inside and out. Coat the outside with foundation tar, paint the inside with something that's waterproof and will not peel. The tanks will sweat on the inside (collect condensate from breath, etc.) - this will run down and pool in the bottom, so you will have to mop a bit.
4. If it is 10' in diameter you will need a lowboy to transport it, as well as an oversize permit. If it is a long way to transport that can add up to a lot of money.
5. The advantage of steel is that you can torchcut and weld a hatch and ladder to it, as well as ventillation pipes, etc-- the disadvantage as I said are sweating and rust. It will also be as cold as the surrounding earth it is buried in, unless you in$ulate it $omehow.
I have 2 like that 8 x 20 now, but I am going to fill one with heating oil for tractor / generator fuel and as a barter commodity. The other I am now slowly filling with filtered reclaimed fry-oil from restaurants (griesel). I only use solar and wood to heat with.
- Basey