Well, I sure appreciate all the replies, there is a lot of food for thought. I hadn't really figured out how to start a siphon with this kind of pipe, but Bing has done it - see his reply:
http://www.pondboss.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=3;t=000165;p=1 As for our pond, we've talked to our "bulldozer guy" who made the dam in the first place and he agrees our clay is very good. With his help we are probably just going to cut the dam to let this water out, then seal it back up.
Thanks -
