Thanks. Mold on animal dropping makes sense.
It's been flooded down there during the winter for years. I finally saw water recently flowing from the center of the crawlspace. I dug down about five inches and there was standing water, seeping in from somewhere I couldn't tell. I put a sump pump right there, and it alleviates the situation - a little. I'm not sure if putting poly down there would do any good. Possibly an underground spring and high water table during heavy rains. The place is a real mess...uneven ground, tree roots,