Thanks BC and Brian for the reply.
The leak is under and through the dam. Yes he put a keyway in (about 4 ft. deep) but I have alot of rock and evidently my clay is very pourous. I drained it myself 2 yrs ago and dug out the bottom. Removed about 3 ft. of rock and replaced with clay and 20 tons of bentonite and sheepsfooted it in. I thought that might fix it but no cigar. Anyway it leaks at the base of the dam from one end to the other and also right through the dam up about 1/3 of the height. It's quite a mess back there but I'm trying to deal with it. No erosion just very wet.
I'm not willing to spend much more on it. Already in for about 22K. If I have to drain it I'll push it in.

Houston Turner