f1sh - did you build a keyway into the middle core of the dam's base?. Water has a tremendous ability to find a path of least resistance even around or between layers of a 12" thick packed clay patch. Remember that this area is under hydrolic head pressure from the overlying water. Amount of pressure is dependent of the water's depth.


aka Pond Doctor & Dr. Perca Read Pond Boss Magazine -
America's Journal of Pond Management