pondsea,
Beautiful area for a pond! I can just imagine it when the grass and trees are green.
Ponds that go downhill with the deepest part right at the dam have special concerns. This is especially so if the water will be in excess of ~10 feet at the dam. The water pressure is so high the dam must be keyed very deeply and the base very wide. If that hollow has a great flow of water after a moderate rain, even more extrordinary precautions will be in order.
Good luck, and keep us posted on the progress. The more pictures, the better!
