Pond Boss Forums INTRO Questions & Observations Looking for input, PLEASE HELP!

Anytime you deal with soils that have some difficulties (like your sand/gravel sides) you have the possibility of a big swing in cost dealing with them. On a bigger pond, I don't see how the potential cost swing wouldn't be equally big.

If you have sufficient clay to line the whole pond a couple of feet thick, figure that approach for the cost. Hopefully it will be the worst case estimate IF the leaky sandy soils are such that clay can be packed on them easily. Like DD points out, lining clay onto the sides of a pile of pure sand or gravel would be virtually impossible.

You're planning a big pond (or a small lake); a large number of test holes are also called for, to try and determine the extent of the clay, extent and nature of the leaky soils, etc.