New 1 acre impound pond leaking (more than a seep) at the toe along approx 90' section. Has wide and deep key, did 2' foot lifts. Compacted slopes and lifts with commercial large CAT vibratory compactor. We have a 15' dug deep section, but most of pond base is 10', have small island with "underwater" bridge. Lots, many, a lot of springs on the upside bank, the impound is approx 10'. Been through 2 thaw cycles.

Wondering if I should try bentonite sprinkled/dumped on the surface, especially around the island and underwater bridge as those are virgin ground. We used a bentonite mat in the deep section only as that base was boney.

Would appreciate ideas on how to solve and if you folks have good luck with the "sprinkle" method of Bentonite. thank you