The way this pond was built, was solid. The rock in the dam I have seen is not porous or sand stone, so it was good substrate fill with sheepsfoot compaction. How the drain pipe was added later, and having personally seen a large void under the pipe where no clay had been makes me positive the leak runs the full length of the pipe, and around the 2 seep collars installed. I have no doubt the "fix" will be digging up and proper reinstallation of an overflow....Not the cheapest fix, but way less than most redo's.

Sparky, in this area, no permission or pond permits required at all, unless at a federal level due to acre/feet of water retained, or toe height of the dam exceeding 32 feet.