I have a small forage pond that is unfortunately leaking. The small pond is at the bottom of a ravine. The leak itself is on the side of the steepest hill that drains into the pond. I believe that the cause of the leak is an underground system that initially fills the pond after a big rain but also drains the pond in the few days that follow. I have attached a few pictures of the hole (both up close and from a distance).

I have tried to plug the hole using a concrete slurry. This seemed to work for a while but it wasn't long before the force of the underground water flowing down the side of the hillside pushed around the concrete and formed another area for draining the pond. Given the steep side and the force of the water after a big rain I am not sure how to plug the leak. At this point I am contemplating buying a large section of pond liner (20 x 30 feet?) and securing it to the top of the bank that has the hole and having it drape over the hole and surrounding area. I think that this 'drape' would allow water to come in through the hole after a big rain but, once the pond fills, the force of the water in the pond would push the liner up against the hole keeping the water from escaping out the hole once the water table drops. In effect, I would be using the pond liner as a check valve of sorts. I'm not really sure what to do at this point. Any advice would be GREATLY appreciated.

I like that idea. The only way that I think it could be improved upon is to smooth out the dirt surrounding the hole so the liner has a flat spot to seal against. What you are planning on doing is making a super large flapper valve.

Other than getting some heavy equipment in there to dig out the hold and plug it, I think that's the only option.

Please let us know how it works. I bought some liner off of e-bay cheaper than I could find it from any supplier.

Thank you for the reply. I'll definitely do all of the smoothing that I can before I install a liner. A couple of follow-up questions concerning the liner option:

1) What would be the best way to secure it at the top? Should I bury the top part, place heavy rocks on it, or secure with staples?

2) How should I secure the bottom section of the liner? If I don't weigh it down some way at the bottom won't it have a tendency to float up?

3) I believe that some liners are toxic to fish. Is there any type of liner I should avoid? How thick of a liner should I get?

Thanks again for the help!

Do you think that the bottom needs to be secured (to keep it from floating up) or is this a non-issue?

I would. Overkill is better if you don't want the possibility of having to mess around in the sloppy part of the pond at some future date. I'm unsure whether the liner will float or sink. I'm leaning towards sinking - that's some heavy stuff!

Sounds like a plan. I appreciate all of the help!