Posting an update.

I ended up using a pail of Damit I was given by a neighbor on the dam, and so far have had excellent results. I was pretty sure I knew the area that was leaking, as I found a a wet spot on the backside. I applied heavily over a 20-30 foot area along the shore. By the time I did this we were losing around an inch a day due to the smaller surface area of the pond. The leak slowed over the course of the past week, and as of today our loss overnight appears to be essentially zero.

I know people have had bad experiences with damit and it’s longevity, so I’m going to keep an eye out for more dropping, but for now I’m starting to refill our lost 14ish inches with the well.