You would be better off to sell the property and find one more suitable for a pond. In this thread the owners of a 35 acre lake spent several hundred thousand dollars to seal their lake. It took 4200 loads of clay and they were very lucky to find it only two miles away.


http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=20;t=002438;p=1#000002


Please no more rain for a month! :|