Update on multiple leaks along toe and dam. I used 15 containers of a pond selaer called DAMIT sprinkled over the entire pond surface, approx 1 acre and extra heavy along the 15' deep end and impound dam area. I've waited over a year to give this update. Their product worked, very effective thus far. Last year we had approx 4gpm loss (we measured along a 100' trench we dug with a trencher) and at that time pond was down 28", after being full over the winter and spring. It took about 2 weeks to plug multiple leaks, and loss was down to less than 1/4GPM. Its a messy process using a hand broadcast spreader and Jon boat. I also used a backpack blower for the shoreline along dam, blowing their sealer 30' from the shoreline.

Now, 15 months later, the rate of loss remains at less than 1/4 of GMP, and all but 2 seeps are bone dry. Pond is full and water is spilling over the manhole drain, most I was down was 2" in early June.

That was my experience, yours might be different or maybe you've tried another product mentioned on this site.