Pond Boss Forums POND CONSTRUCTION Soil questions How to fix a leaky watershed?

My half acre pond is down probably 3 ft since the time I bought the property last summer. The locals tell me the problem is the pond "leaks" and after hours of searching for seepage around the hillsides (pond is on top of a hill) I never found any seepage. So, as luck would have it, I camped out on the property last week during deer season and got to see what was happening during a heavy rainstorm. The pond isn't leaking, but the watershed is!

The pond is built at the tail end of what was a small strip coal mine. The effective watershed is a little over six acres and looks like a amphitheater (sloped on three sides and then flattening out by the pond). What I saw during the rainstorm was water running down hill toward the pond and then disappearing into holes in the ground. The draining of water into these holes was noticeably loud, like the sound of someone emptying a bathtub. One hole was about two inches in diameter and the other was about twice the size. The area around the holes is a weedy field and the surface soil is a heavy clay.

Obviously the water has found its way down into unconsolidated subsurface soil and rock structures that are backfill for the mine. I have no idea where the water is going, but I do know that it isn't making its way to the pond. I found other holes too and all are at an elevation above the pond water level. What's really strange is not all the holes are at the same elevation!

I feel if I can plug these holes, the pond will recharge and even increase in size. I'm looking for any input about how to solve the problem. In the short term, I took a shovel out there and manually tamped heavy clay into the holes. Long term I am considering using a dozer to move soil out of the area with the drain holes, line with Bentonite, and then cap. But that is the costly solution. Anyone have ideas about how to fix the watershed leaks or had similar experiences?

Thanks!

I wouldn't use bentonite. Pack those holes with native soils, or with rocks packed with soils, or try to divert flowing water. Consider building small diversion terraces, guiding water away from areas where the holes are, more directly into your pond.

Bob,

Thanks for the advice. I noticed my pond rose about 6 inches during a week when we got far less than 6 inches of rain, so I'm thinking that plugging those holes may have helped. I'll plug the rest and see what happens.

As I mentioned in my first post, the watershed is former strip mined land and the Indiana Dept. of Natural Resources did the reclamation work. They installed terraces and berms to divert the water to the pond area. All I have is about an acre or so of 'leaky' ground that is catching the runoff. I thought about laying some tile through this area to 'bridge' it, but if I can stop the leaking the pond will eventually enlarge and cover the leaky ground. Thus the interest in stopping the leaks; a double benefit of greater depth and surface area.