I’ve filled in an 18′ x 36′ pool and am going to build a steel storage building over the site. I’ve left approx 6″ from the top of the pool sides and am wondering how long I should let the dirt settle and what grade cement to use and if I should use rebar or other strengthener? Also, is a 4″ base over the steel sides of the pool enough for a footing for a steel building?