rsch1,
Some clues - BUT YOU NEED to REVIEW THE PERTINANT CODES FOR YOUR DESIGN. I am well satisfied you've been pointed in the appropriate direction.
I think, "not saying for certain", YOU need to verify tanks of the material you discuss "may be acceptable underground only, based on certain conditions."
Aboveground indoors - sounds very illegal.
All materials in the diked area would be considered as the most flammable after you get the MOC correct.
These are only a couple of items that come to mind - obtain the Codes recommended previously and become very versed on what you intend to provide.