PondsForFun,
My take: Cover the small spot(all around it as well)with 2 feet of well packed clay...your operator should have done so initially. Bentonite has mixed results, but if you want an insurance policy and since it is nearby, you might be able to get it cheap. The shallow places should be okay, just be sure you have good thick clay everywhere there will be pressure from water to escape.
How are ponds in your local area as far as tendencies to leaking?
