an improved fire - resistant above - ground storage tank for flammable and combustible materials is fabricated from steel plates of at least 10 gauge , the sheets being made from a ferrous alloy having a maximum of approximately 0 . 15 % carbon and a maximum of approximately 0 . 8 % manganese and the steel plates welded in a specific way resulting in a tank that can withstand a 2000 ° f . environment for a minimum of two hours .