I need some advice as I'll be the first to admit I'm not a pond building expert. I looked at a 2-acre lake this weekend that won't hold water. Actually to be technically correct, it's just a dry hole in the ground with a small puddle in the deepest area. The owner wants to seal it, but didn't like the $35k price tag he got from the bentonite folks, particularly with no guarantee.
Upon examination of the site and pictures of the construction, I determined that the dam appears to have been constructed with a clay core and the leak is no likely going through the dam, but more likely under it. The lake was constructed on a small creekbed. It's quite deep, 15-25' over 75% of the area, but it leaks all the way down in a couple of weeks. It has filled and drained numerous times in the two years since it was dug.
The contractor dug through quite a bit of good clay which was used in the dam, but dug the lake down to bedrock in most places. Several trees were left in place on pedestals (for lack of a better term) to serve as cover. All of the timber was put back into the lake when construction was complete. So what is left is a big hole in the ground, with dead timber everywhere.
My assessment is this: The pond was dug too deep (obviously) and the clay that should have been used to line the basin was instead used to core an excessively large dam. The bedrock in the basin is probably fractured, and the water is leaking through some large cracks and surfacing about 250 yards downhill past the dam. Some leakage may be occurring elsewhere, but the rapidity of leak-down, combined with the fact that the lake goes almost dry, leads me to believe that the leak(s) are in the bottom of the basin.
So what to do? Bentonite or a liner appears to be too expensive for the landowner to stomach. Obviously whatever course he takes, the dead timber needs to be removed. The trees on pedestals look cool, but could they be contributing somehow to the leak? They'll probably have to go if the basin is sealed.
I've looked at the ESS-13 website, but I'm not convinced that it will work to seal cracked bedrock. It looks like additional clay has to be brought in regardless for this product to work. Has anyone used this product in a similar situation with success?
Perhaps the most straight-forward solution would be to truck in clay and line the bottom of the tank. A reduction in depth would not be an issue, because it is already plenty deep. A loss of 5' even would not be a problem. Would this work, and if so, how much of a clay blanket would be needed?
One last question. He indicated that a neighbor built a large lake and lined it with caliche when constructed.
He compacted it and wetted it. I saw the lake, it's full and apparantly stays that way. Has anyone heard of this technique? The concept is that it sets up like concrete and forms a barrier that way. The reason he asked is that I believe he can obtain the same caliche for his lake. Might this work?
Sorry for the length of my post. This one's a doozy!
