Good morning forum, I'm currently in the middle of a project where I'm installing a new chemical storage tank outside. I need to lay a new concrete slab for the tank to lay on. My question is how thick should the concrete slab be? The tank will be stationary, when filled it will weigh approximately 4600 lbs, plus some piping and other equipment attached to it. The tank will be stationary and the pad will be approx. 5 ft x 5 ft. Is there some kind of formula or ratio I can find, or is 4-6 inches just a standard?