Pond Boss Forums POND CONSTRUCTION Building a dam Always Core the dam?

We finished our pond at Thanksgiving last year. Our soil is deep sand, but we built our pond in a draw where the sides of the ravine had clay just below the surface and we had the dam span these two sides of this wide draw. The dam is nearly 600 feet. My contractor planned on coring the base of the dam, but decided against it when he determined that the trench depth required was not reasonable: at the lowest point of the ravine he would have had to dig down 15 feet or more to reach the clay. Further complicating it was the fact that there were active springs above that clay. Instead he pushed as much sand as possible to the back of the dam site and dug as deep as he could with the bulldozer. (actually he got his D8 stuck for 2 days in it) He then started working from the sides and back pushing the sand/clay mixture towards the dam and kept building it up higher and higher. With this method the dam actually extends halfway into the center of the pond and is at about a 40 degree angle. At that center point he was deep enough to now be at clay level. All told, he dug about 12 feet down and the dam was 10 feet above original soil level for a total of 22 feet of depth at the midpoint of the pond. Overall the pond is about 2 1/2 acres. The dam is probably as wide as 100 feet at the base. Steep on the back, very slight angle on the inside of the pond. I was concerned about the lack of coring, but I must say, we are half way full now and we are losing maybe a half inch a week in depth, if that. Based on Eddie's post about the weight of the dam creating the seal, the logic of this design could be the increased downward pressure on the dam because of a more gradual slope. The dam surface has no less than 3 feet of clay on the top of it. I'll try and figure out how to put the construction pictures on this site to illustrate the concept. Hopefully this will continue to work. Our depth is about 10 feet at the deepest point - I now hope we have enough rain to fill it another 10!