I consider redoing an entire dam a pretty drastic step.
I've just looked at your previous posts. It seems to me that if the pond, now lower because of drought, is not currently leaking, your problem is not at the core.
I think I would try to find the porous spot that is allowing water to escape into the dam. Just recoring without figuring out why it only leaks at a certain level wouldn't, IMO, fix anything. Admittedly, the weight of the water does build increased pressure.
To me, a pond is nothing more than a container of water built of somewhat porous material. Water always looks for a place to escape impounding at the place of least resistance. If it were a bucket with a hole near the top, it would leak out the hole and run down the sides to the bottom. Redoing the bottom of the bucket wouldn't help.
You stated in a previous post that you have only clay; no rocks or sand. It is my opinion(and I could certainly be wrong) that you have an area of the dam that is porous. When the water drops below that level, the dam doesn't leak.
That's why it appears to me that recoring wouldn't work. However, to recore, you would have to dig out and redo the whole dam. Why not figure out the level that it stops leaking and look at the entire area just above that level and fix that? You might find that one area is porous and it extends down through the core. There's no real way to tell that.
Thanks Dave! I agree that recoring the entire dam isn't necessary. You've confirmed my (inexperienced)thinking that I've had all along. While it's true that there was no rock or sand involved with the construction, I remain puzzled as to why it's leaking in this part of the dam.There was a tremendous amount of black dirt available (topsoil from the hills above the pond)& it's possible the builder didn't use enough clay in the area that's leaking. The leak is located about 2- 3' below the top of the dam in an area approximately 4'W x 100'L. As you've stated, repairing the porous section is where I need to focus my attention......
Probably should mention that they buried some of the trees they removed during construction, behind the dam. If you look closely at the first pic I posted (of the full pond), you'll see a slight dip in the center of the dam where they buried the trees. The actual leak is to the left side of that dip though......
