Hi, I'm getting two hens soon and I'm preparing a part of my yard for the coop, their run and a small, secure enclosure when they're not roaming in the yard. Storey's Guide to Raising Chickens suggests 2" of sand as a good base for the pen. I looked online and Quikcrete, a manufacturer of sand for masonry and children's sandboxes, warns that it's toxic. They recommend keeping it wet to avoid inhaling too much dust. I can't think that's good for chickens. I live in Sunny San Diego so there's not much rain. However neighbors who use mulch seem to have a tough time keeping it clean and dry. Right now I have pea gravel over blackout paper over the Earth. Other options are compost or mulch from the City Greenery or DG from the local Building Supply. Any suggestions? Thanks!