Calculate Concrete Slab for 30,000 gallon stainless steel tank

We need to determine what size of a concrete slab for a 30,000 gallon stainless tank. I have attached pictures and have calculated that the area that the tank touches the ground at 33 square feet. We need to know how thick to pour the slab and if any other treatments are necessary (Rebar, fiberglass, etc) and what PSI for the concrete. These would need to meet American Engineering standards so that if the entire project gets engineered the calculations already meet what is necessary for a permit. Total width of the tank is 13 feet. The estimated weight is 20,000 lbs of the tank.