Bill,I'm not quite sure what your mean about ''keyway'' unless you mean like scraping the top soil to blend with the soil i used to build the dam? I just dug down about 3 foot until I got to a little clay and piled it on. The clay was holding puddles of water before it filled and it kinda like holding water just enough to make it hard mess with without draining but not enough for desired depth which is 3 - 5 foot. I hope I can figure something out. Also I have a spring in the other half of the pond, so it's gonna keep on having water in it, so i'm concerned even if I break the dam and drain it I would be able to get it dry enough to make a good blanket. But your right that water sure did find a way out. I knew something would go wrong. doesn't it always! lol