My property line is in the middle of the creek, so it wasn't possible for my pond to go there. I dug mine out next to the creek with a long dam around two sides of my pond. The creek flows year round, but the height changes quite a bit from the amount of rain we get. I put a drain into the bottom of my pond that goes into the creek. and is just a few inches above the water level of the creek. My pond is 12 feet deep when full, so my water level is 12 feet above the water level of the creek.
I had some concerns that the water would seep through the bottom of my pond and into the creek. While digging my pond, I was in clay the entire time except for one area that was sand. In that area, I dug out the sand extra deep and packed it with clay.
It might be that I was over every inch of my pond so many times with my dozer that I compacted it and sealed it from leaking, or it could be that the clay was already there and is working perfectly at holding water. I'm not knowledgeable enough to know for sure, just that my pond doesn't leak into the creek.
I have a yardstick stuck into the spillway that is covered up when my pond is full. I can look at it to see exactly how low it is when it's not full. I have a steady drop during the heat of summer, but when it's cooler out, there is no noticeably drop in the water level. This tells me that I'm losing water to evaporation, but not to a leak.
If there is clay, you can move it around to seal your pond. If you have to truck it in, then it gets very expensive. As for the layers, that should be easy enough to overcome with a good layer of clay to create a bowl inside of your hole in the ground.
Good luck,
Eddie
