I have a 500-gallon fuel oil (diesel) tank that I put in a few years ago. Poured a concrete slab with heavy rebar with containment area. Placed the tank on cinder blocks that I cemented to the pad, which raised the tank 6 feet. This allowed for gravity fed 1 inch copper line to the house furnace and supply line for the tractor. One thing to keep in mind when picking a location is how to get the supply truck to your tank. In my case it is in back of the house and we have underground sprinkler system and I did not want the delivery truck on the lawn. I put the pad in a location that the delivery guy could run the hose through the garage and out the back door to the tank.
PJ