I have been on this thread before and I am now considering putting some Class I sand down in the run as it packs down nicely and then some finer sand over it. I think it will be a good drain base and I am not worried about freezing as the soil base feezes also and I know it would be much easier to clean up from frozen sand than frozen dirt. The ground gets pretty hard when it freezes. I am currently using dried pine needles and leaves that I stockpiled last fall and when it breaks down, I put another batch down which they love picking through. I don't like the idea that they will be deprived of that fun but it would really mess up the sand. Any ideas on my plans??