Just as another point, make sure and get a pond building expert to your site to be sure it is even reasonably realizable. If you have a lot of sand in your soil, it may be more economical to use a liner than trying to bring in clay, and a liner is pretty much a perfect seal. With a liner, you may want a smaller pond, and if your water table is high, you can have a shallow well to pump cold water into the pond for trout.
Get the book offered on this site, "Perfect Pond, Want One?" it is a fun read, and tells a lot of stories of projects good and bad and gives some great info on how to choose a contractor or a primer on how to build a pond.
