I have seen a whole track built from astro-turf(like the green carpet mentioned above) with a thin bit of sand mixed into it on a video, I think the vid was made in England or something but as gay as it sounds the guy's were hooking up very well and the poster said it was easy on tires AND it drained water EXTREMELY well, and it had plenty of cush for the big jumps.. It was a very cool looking track andvery easy to maintain..I was very impressed, the guy who posted it said that he lived in very rainy area and he said an hour after any rain they could run on it, which is a great point--hardly any cancelled races..