If you decide to use clay on the pond bottom I would ask M.Otto about also using or mixing bentonite (as insurance) with the clay for lining the bottom. Otto is one of the best for assessing leaks and repairs. I trust his highly experienced opinion. Bentonite tends to work best long term when water always covers the bentonite compacted area. Once the original soil crack with bentonite dries out (evaporation) in upper near surface areas the leak often returns. I would use the compacted bentonite-clay mixture on the bottom as a much more likely way for a good long term fix compared to just adding bentonite to a pond containing water and hoping bentonite will find its way into the cracks in the limestone bottom.
If the pond does not receive water, how far will the water recede before the level stops going down?. If the leak is in the limestome pond bottom, the pond should eventually completely drain dry. If the leak is mostly in the upper soil layers the water level decrease tends to stabilize at some level or depth.
Last edited by Bill Cody; 11/18/13 12:09 PM.
