Bob is right: you're going to get speculative ideas on what is meant. Here are mine, though I'm not a chemical safety engineer in any way.
I'd just design the fuel depot area much in the same manner as an evap pond. Mount the "tarp" (see what I mean below) inside a frame of 2x4s so the edges are elevated the edges (the "berm"), and place the fuel barrels, etc. in the middle, maybe on a pallet placed over a small tarp (so it doesn't damage the berm plastic) to keep it off the surface. Designate a pouring/siphoning area so you don't walk over the "tarp" and possibly damage it, and put a pile of "kitty litter" there to reduce splashes.
Most of that is merely to ensure that whatever small amounts spill out of the fuel container during siphoning/pouring, as well as small leaks, will not reach the playa. Containment for a major spill will be impossible, so it's mostly just small spill/drip-mitigation. How much of whatever is needed will depend on the amount, geometry, etc. of the fuel storage. Exact quantities--I have no idea. It's like exact instructions for evap ponds. The fire extinguishers--I don't know how effective those would be for something major, but still good to have around just in case.
For a tarp, I think neoprene tarps are gasoline inert, but they're pretty damn expensive ($120 for 6'x8'). You can probably do fine using a polyethylene tarp or sheeting as a barrier to contain the drips, etc. as polyethylene has decent chemical resistance to gasoline and other chemicals; it's also cheap, and you can deploy lots of it as needed. I don't think vinyl tarps are up to the task of chemical containment, but putting some sort of plastic tarp below the entire containment area might be a good idea just to keep the depot separated from the playa surface directly.
It'd also be a good idea to keep the fuel shaded so that it doesn't vent too much.
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