Not a professional but have worked with ponds a good bit, probably need a little more info, mostly as to what kind of soils do you have above that clay line at -25' theory would believe that if water table is at -11', in other words, if water runs in to maintain that level I would assume water would also run out to that level, with out a clay or restrictive liner.
Hopefully some of the professionals on this site will chime in and answer your question. Good Luck!
