Thanks everyone. Lately I've contacted Seepage Control, Inc. about lining the lake area with ESS-13. They have agreed it will work in my lake and would guarantee it. That's very promising, but the process is not cheap by any means, especially in a 15-20 acre pond. Has anyone had an experience where the lake bottom, dam, and one side was impervious to water, but then lost water to a weak side??? I guess I am going to try and move forward with contacting a contractor and get ready to build the dam. If it comes down to it, I will have to get Seepage Control involved. Anyone have any experience with them? I guess I am happy that I can do the project, although at a price. I think I might do some more holes throughout the area and check the results. I have looked at topos of my area and there are plenty of lakes and ponds. Why me???