Bullhead...
From your pictures, I see good rich black farmland in your dam, but no clay. Even with an overflow pipe and a spillway, I wonder if the water won't eventually work its way through the black dirt and cause a failure. The guy that build my dam went to great lengths to cut a "key" deep below the waterline and pack it with clay. That clay seam carried through all the way to the top of the dam. Your pond is a lot smaller, but there should be some guys on the forum who could give you an idea of how much clay should be in a dam your size.
