Bob, you will need to mix that Bentonite with the clay, and compact it in at least two feet deep on the bottom of your pond, to be fairly sure of it working. I tried lots of bentonite poured on the banks at the waterline and on the dam below the waterline, and it did not work for me. I have a leak from the full pool level, extending to about 30" below, and haven't been able to fix it. I am thinking of either a vibratory roller or a cutoff trench in the dam.