When we moved onto our farm one of the ponds didn't hold water. We discovered that the drainage pipe had rusted severely and allows water to leak through the dam wall.
The pipe is about 4 feet wide when it is vertical (where the height of the pipe determines the max water level of the pond), and then it is about 2 feet wide when it runs horizontal across the bottom of the dam wall.
According to my research metal drainage pipes often rust, and eventually need to be replaced. There are 3 common solutions.
1) Dig out pipe and replace it with a new one. In the process you have to excavate a large portion of your dam wall
2) put a new pipe inside your degrading pipe and then seal the space in between with concrete or something.
3)Take out as much of the pipe as possible, without digging out much of the dam wall, preserving the dam wall. Then cover back up with packed clay. Then use an alternative means of drainage.
This sort of system seems quite common. If this problem occurs and goes untreated, eventually the erosion can become major enough to blow out the dam. I now detest such a technique, I want my ponds to last generations, not the lifespan of a metal drainage pipe.
I'm choosing option 3.
So far we took out the vertical piece of pipe. Now we are left with the rusted horizontal pipe that goes bellow the dam wall. We are considering building forms and capping the end of this pipe with concrete, and then backfilling with our best clay.
Anyone have experience with such an issue? Any thoughts to add? Is capping with concrete over kill? What should be done? THANKS A BUNCH!