I made the sand bags out a material called paper clay and used the back of a piece of hardboard to give it some texture. The floor is a tiled plastic sheet that I bought at a local hobby shop, you might be able to find it at a craft store too. I want to add rubble in between the pieces of the floor, and do something for the outer base.
The railing and ladders are made from 1/2" wire mesh that I bought at a Hardware store for 10 bucks, and I still have more than I think I will ever need.
more pics of the Power generator with my models for scale.