One of my geology professors was doing his dissertation for his doctorate a while ago (years, I don't know how many... he's old) on the San Juan. He spent weeks on the river doing field work. When he floated past Clay Hills, few people if any, knew about it. He ended up running it when it was only a 6 or 7 foot drop, but it continued to get bigger. I think he said something about someone dying on it later that year. Now there's a sign at Clay Hills that says not to go any further. I guess it's around a 30' falls now, maybe more. Oh, and it's Reservoir Powell.