Hi all.
Some of you have seen me here before, many times, seeking advice and updating the forum about a leaking lake I've been working on for about 20 years now. Yes, twenty years.
We left off with the contractor coming back for the third or fourth time in Feb of 2012. We dug into the levee and found sand. So, they took a huge track hoe and a dozer and dug out the sand, which took nearly two weeks. We probably dug sand for over 200 feet down the top of the dam and probably 15 feet wide and mover ten feet deep. We then took a 17 yard dirt pan and filled it back with good clay. The back side of the levee did not show signs of water this year, and I believe we have fixed that problem. We dug a new core ditch in front of the old core ditch just for extra.
Still, it was apparent that the lake was still leaking once I got it full again. I didn't worry too much over this last year since I was prepared to give it the benefit of the doubt and let it settle and self-compact for a year. This is now the near end of year two and although it took longer, the lake eventually dropped to the level where it always falls, and how appears to have quit falling. Right in the same place.
So now it's back to that mystic spot where the leak is. We never have identified exactly where it is. Water must still be getting into a sand vein or pocket someplace and seeping in and around till it leaves, causing the leak. We may go around it with a metal probe, but we've done that many times in the past. We found several sandy areas, but when we dig down with a track hoe, sometimes five feet or more, we hit solid clay that is almost as hard as concrete. We added clay over these areas, but it still wasn't enough. Now, what I think is happening is that the water is getting into these sand veins and routing around to a leaky spot in a different location, and draining out from there.
The only thing I can think of now is to drain it down another couple of feet to the bottom pond basin. When we get it that low it looks like a bowl on the bottom. It's very distinct where the basin is. I�ve never known that to leak. In fact, I�ve never known it to leak more than where the level is now. There is something at that elevation, somewhere, that we can�t find that is causing the leak. Now, I think my best option is to plate over the known sandy areas with more clay soil, lay plastic all around the lake to cover that band, and then add clay soil on top of the plastic.
I give a neighbor all the hay he wants in return for me getting my pastures mowed every year. He has a bulldozer, a good sized John Deere and a 5 yard dirt pan. He'll do the work free if I buy the diesel, so we already struck that deal.
I can order 10 mil black plastic PVC sheeting, 20 x 100 for around $140 a roll. This time I want to overlay as much of the lake bottom as I can. And, I want to overlap it, so the width will be around 35 feet wide, instead of 40. This would need a five feet over lap.
The plan now is to open the gate valve and drain the lake down to pools basin level soon. Then take the dozer and push my fish holding brush piles out into the basin. I won't lose much cover -- it will just be out farther.
Next, I want the dozer to make a smooth surface all around the lake from the basin up to the high water mark. Here, I want to add more clay to the areas I know to be sandy, then lay out the plastic and overlap it. Then, using a front end loader we'll go easy and dump more clay dirt on top of the black plastic. We'll work our way around on mats, and also do a lot of shovel work to cover the plastic at least six inches deep.
To my thinking, a five foot overlap should be plenty to keep water from running between the plastic sheets, especially since we will have it weighted with clay dirt. I can't imagine more than a tiny seepage, if there is a seepage at all.
Before we start I wanted to ask some of the pros here again about my plan and the use of plastic in a lake bed. Will a five foot overlap be more than enough to stop anything but a tiny seepage? Seems to me it would be virtually waterproof.
We'll be going about 800 feet, maybe up to 1,000 so I can't find, or think of, any cost effective way to join the overlapped pieces with an adhesive, such as tape or roofing tar. Even then, I don't feel like either would last long under water.
I can take a modified one point chisel plough and pull it around with a small tractor, pulling a small trench right where I want the over lap to be. Then when I lay the plastic and overlap it I could anchor it in the trench with 1/2 rebar. That would crimp it pretty good, and I just can't imagine how there could be any significant seepage with that arrangement.
Also, I'd like information from the forum members on how long will 10 mil black plastic sheeting last under dirt, under water, and never being exposed to sunlight or harsh temp changes. I hear that plastic bags last decades in land fills, with no significant break-up. I know PVC is inorganic and will lever truly compost, but from what I'm reading, if you have it underground that it last indefinitely.
We have the dozer on site now, and the tractor and dirt pan will be coming over next week. We'll have that, plus two or three tractors with loaders that we can use to dump clay dirt on top of the plastic. I might even use 4 x 8 plywood sheets as a mat for the tractors to get out on the dirt that is covering the plastic, so they can gradually work their way farther and farther out. I can't imagine how the plastic would even feel the pressure of a tractor tire over them if I use mats like this.
So there you have it. The saga of the leaky lake continues. I've tried everything else, but I can't see how it could leak if I cover the bottom with plastic. Still, I'd like your thoughts.
Oh, and for those of you who asked months ago about the contractor coming back and the fee he charged for digging out the sand and hauling and packing in clay dirt, we had a firm yet friendly meeting of the minds and he didn't charge me. We did some other work around the farm, which I paid for, but the discount would be just about right to cover the cost of the back hoe, the dozer, and the dirt pan to correct the sand levee problem. Neither of us was totally happy, but I understood his side and he understood mine, and we've done a lot of business down through the years and when I mentioned a discount he didn't argue. I made an offer, he countered, I accepted, and then paid him with a hold harmless release from any more liability on the pond .
That's the update on the leaky lake saga. Let me know your thoughts and suggestions, especially on lapping the plastic sheets, and how long they should last underground, underwater, being packed and insulated from extremes in weather and any contact with direct sunlight. I'm guessing in my climate that if I could probe down 6-12 inches with a thermometer in any local lake bottom that the temps would be in the 70s almost all the time.
Some of you have a world of experience with soils and lake constructions, and some of you just might offer suggestions that make all of this work better. I�ll have a tone of pictures and video during this renovation, and I�m hoping that not only will it fix my leaky lake, but that it will be of benefit to others with a similar problem.
Thanks in advance, and I really look forward to hearing from you.
�Bill�
