Pond was built november 2002 don't have big water shed. Took almost 1 year to fill and was the best thing for low area in my yard.contractor used excuvator to dig keyway then used tractor to pull scraper to build dam, plus dozer.Now after it filled last winter, starting in about june noticed some damp spots on back side of dam,and now i took a measurment and pond is lossing 1 and 1/2 inches every 3 days but not alot of standing water on back of dam, but can tell it is coming from pond. pond and dam are all clay. called contractor and he said he will get some bentonite and sprinkle in pond to seal. My question is, has anyone done this with success,i don't want to end up with a mud puddle but this 1/2 acrer pond cost me some good money,and want it fixed right. please help