I'm guessing that the dam wasn't compacted in 6"-8" lifts with a sheepsfoot roller? When you say "The soil used in the dam is all clay and rocks that were dug out." does that mean that the rocks that were dug out of the pond were put in the dam along with the soil?

If so, I'd recommend draining the pond, removing all the riprap from the back side of the dam, removing the dam, cutting in a core trench and properly constructing the dam (including properly compacting the dam) without the rocks in the soil.

Better to bite the bullet and do it now vs. having the dam wash out on you further down the road when you have fish in it.

I know that's not what you wanted to hear, but if the dam was not properly compacted when it was built there is no way to "fix" it that I know of.

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