Bruce,
Now I have a question. In one of your small ponds you had problems with air bubbles under the liner -- or was it water under the liner that made you liner do funny things? I talked this over with a local liner supplier and he thought you may not have allowed the liner to freely get pulled in as the water filled it. He said one should not trench the outside edge of the liner until the pond is entiredly full.
Was this case or were there other reasons? I know I get water under my well pit liner every spring that seeps in underground which can't be helped. I have a sand vein underneath it.
Good question. I believe the name usually given to that is "whaleback" or "whalebacking". The number one way to avoid it is to have the liner be one perfect piece. I was getting water through the seam immediately. The other way to avoid the dreaded whaleback is to do exactly as you described and get the pond at least partially full before you begin the process of trenching in the liner. One good thing though, is that those liners are seriously tough. Almost untearable.
