Dave,
The original spillway eroded, this was my solution. the discharge/drain pipe will maintain water level and handle moderate rain fall. The spillway would handle excess water during heavy rains. I don't know the original design of the spillway or much else about the pond other than it was built in the 60's and then forgotten/neglected until now. I'm a novice where it concerns ponds and thought if one is good then both would be better also this design would hopefully eliminate future problems. I'm open for suggestions I am by no means a authority. Paul