We are in a siut against a contractor that biult a 3 acre pit. I wish I'd found this site BEFORE our first attempt. Get the lacal USDA/NRCS pond expert out there and let him supervise the repair(if he's willing) If the dozer guy dug down to the water table or underground stream then stopped and since your dam is built you will have to either dig a trench in front of the dam till you find good clay from end to end and line the eintire pool are with 6-18' laryers of compacted clay. Been there-done that-Now have a 4acre pond SEALED! other option is to line the pond--WAY too expensive. Third and last is probably to take down the dam. Call the NRCS.