Thanks to everyone for your suggestions. I was going to try include some pictures to show the problem in case that would be helpful, but so far no luck.
I used some epoxy putty and some FiberFix Tape to hold it in place. The leak isn't stopped, but it now is about 8 fl oz per minute instead of a gallon or two per minute.
If the pond is 30 feet deep, the drain pipe may be another 5 to 10 feet lower than that, and it is not a straight shot, since the drain line with the valve points in a direction that doesn't intersect the lake.
Unscrewing the valve from the pipe end may be difficult since it is close enough to the stream bed that the valve handle would hit the mud. Also in looking at the valve I have doubt whether the handle would turn to open the valve.
If I can get the pictures to post they might help.
Thanks again.
