Hi Mike, when I designed my layout, I was concerned about using sand since it might get onto the tracks and into the mechanisms that run on them. That may not be valid but it was a concern for me. However, since I was building my display using art foam, I found some that was green at "Michaels art supply". It works well where I want it to be green and I painted the rest a soil color using latex paint. It's a very fine dense foam, not like those found at home improvement stores which is lighter and more porous. You can also make ponds, rivers, etc when using foam. I used the 2" think version. Then bridges can be used realistically. Take a look at some of my pics from "Equity Junction" and look for the "green. Good luck, sounds like you're having fun. Bob