Esshup,
Interesting suggestion on the epoxy injection. After looking at the fractured natural rock outcrop that used to form a natural dam, I'd rather leave it alone and just place a large gabion at its upstream base. "Repairing" it and adding a concrete dam would take too much away from its natural character. I think I'll be quite happy with just the series of sediment dams and the one larger pond way downstream. That larger pond will be easier to build, more likely to last, and be considerably larger and deeper.
Focusing on just the one pond, instead of stretching my resources to build two, seems to be the wiser play.
