I'd siphon the pond down below the inlet. After you do that there should be zero water flow. If there is any at all the pipe is leaking.
If you stop flow then you stop erosion. Since the water is not leaking out around the outside of the pipe that end is still sealed. I'd consider trimming off that bottom end and welding on a cap.
Then I might mix up loose concrete and fill that pipe.
Then run a pipe at water level through the dam, and run it down the face to the bottom. A 12 inch pipe will move one heck of a lot of water. On the pond end put on a tee followed by an elbow, both pointed up.
Last edited by garryc; 04/23/14 10:37 PM.
