Walrus
The separation is dictated by Fire Code....The NEC is dictated by Fire Code.

I was installing power to Propane Pump Station for the pump and a Night Light at a local Mini-Mart and could not find the code in the NEC book. I found it in the local County Code. Its been so long since I've seen it I cant recall the the artilce, but itwas "cut and paste" from Fire Code. There is a 10'-00" envelope that follows the contour of the tank, anything inside or passes through that area is Class 1 Div 1.

Rob