Well OK ... Truth is, it wasn't quite as easy as I first thought, but I've been continuing to do battle with my leaky pond using nothing but a baseball bat and my pond is 3 inches from full and the water is still rising. I'm still crossing my fingers, but it looks like I may have the problem solved.
Here is what I learned in the process.
After the first beating with the bat reported above, the water came up about 6 inches from it's previous level, but then even as the heavy winter rains began, it would gain water and then loose it at an inch a day, back to about the level it came up to after the first beating.
There is a small seasonal creek on a hill above the pond so now it is running it is easy to fill the pond with a hose.
After it was filled it would loose about 4 inches the first day and about an inch a day after that, leveling out at about 3 feet deep with 3 feet of ugly waterless embankment. In a 6 foot deep pond, this is a real eyesore. As there is water visibly trickling in from the back slope above, I could see I was loosing a lot of water somewhere, and at this time of year, when everything is full of water from winter rains, this is not good news.
After filling it and watching it loose water a few times, on the theory that the leak was close to the water line where the water leveled off, when the water was close to leveling off, I began going along the embankment at that level looking for anything that might be a leak. I developed a technique involving a thin piece of clear plastic tubing and a mouthful of canned milk which I would squirt from my mouth into the tube releasing just a few drops to the side of any small hole or crack I saw on the embankment just below the water line. To my delight I found a couple small holes the size of my little finger where there was a visible current flowing into them .
It seems like knowing where you have a leak is 90% of the battle.
One thing I noticed once I located these leaks, is the dam in that location was slightly softer underfoot than in other places where it has really firmed up over the winter. So that can be one clue if you are trying to locate a leak.
In one of the leaks I tried to stick my finger in it and found that part of the dam was frighteningly soft and squishy compared to other spots and I could easily continue to push my hand and and lower arm into the soft clay.
So I drained the pond as completely as I could and I let it sit and dry out a bit for about 10 days. As I waited I got a hold of 5 50 pound bags of sodium bentonite.
My plan was to drive the baseball bat like a giant peg into where the leaks were, fill them with bentonite, stick a clay cap in there and hopefully no more leak.
It wasn't quite so easy. In the place I previously shoved my hand, there was about 3 square feet where the dam was very soft so I ended up repeatedly making 2 foot deep holes with the bat and filling these with bentonite granules . The benonite helped absorb the water in the sloppy clay an made it stiff enough I could then beat this area firm with the bat.
I did this same thing in the other area where there was a leak, though the mushy clay are here was only about 1 square foot.
I thought I had my problem licked, and with great hopes I refilled my pond, only to see it once again loose 4 inches of water in the first day.
What a crappy feeling that was. I felt completely defeated. I had no idea where it was leaking or what I could ever hope to do about it.
Yesterday afternoon I wandered out there, feeling resigned to living with an ugly ½ full pond on my tiny piece of land. The water was only down 4 inches from full but I knew it was still leaking at the same rate as before. Just for something to do I began wandering along the pond edge looking for anything that might be a leak up at the level the water was at. It only lost an inch a day after the first 4 inches so I figured there might be some leak up higher too. I found a small hole the size of my little finger, under about an inch of water, and by making little clouds of clay with my fingers beside it I noticed it seemed to have quite a suck. I still had 2 bags of bentonite left so I dropped a couple granuals in the hole and saw they seemed to go into it with more speed than just floating to the bottom.
Seemed to be a substantial leak. I wondered if it might be part of the problem. I wasn't expecting anything so close to the high water level.
So I got a 4 foot long and two inch wide stick and pushed it into the hole to see how deep it would go till I hit firmer clay. I easily pushed it down 3 feet and as I did so I saw a few air bubbles come up from about 3 feet under the water suggesting this leak had a few connections further down the dam and far below the present water line.
When I pulled the stick out of the hole, the water began really pouring into it, with enough force a pine needle over the hole began spinning round and round, like a sink when it's draining. So I got my trusty baseball bat and pounded it almost it's full length into the hole and when I pulled it out there was still a strong current running in there so I began pouring in benonite .
I would pour in a whole small bucket and then pound the bat in again to force it deep into the hole, The bentonite tends to ball up once it hits the water and can make it look like the hole is plugged when it is just plugged at the top. .
After pouring about 4 small buckets down this hole, and using the bat or stick to force this deep into the hole and seeing it disappear, and the water still pouring down in there, I began to wonder what was going on. It seemed maybe the bentonite was going into such a big underground stream it was just getting washed away. I thought maybe there needed to be something more solid so I broke some chucks of firm clay into pieces resembling a bite size piece of chocolate and once I had ½ a bucket of that, I mixed in granular bentonite as the other 1/2.
I slowly poured and shoved another 3 or 4 buckets of that into the hole pushing it down with the stick, it all still seem to be disappearing though it was beginning to slow down and only the smaller stick would go all the way into the hole. . Then I threw in a few two inch long by 1/8 inch wide strips of landscape fabric. I was thinking, what plugs up my sink ?
A couple more buckets of bite size bits of firm clay, bentonite and the stick packing it in, and the hole began getting solid and I was able to fill it.
Then I went a few inches beside it, where I had noticed some air bubbles when i was poking around on the first hole, and I found another soft spot so I repeated the whole process there.
As a grand finale I repeatedly jumped up and down on the dam over where I had made the repair and it did sink an inch or two.
I wasn't very hopeful I had really stopped the leak, but today my pond not only hasn't lost any water, it is an inch higher, and is 3 inches from being completely full. It may be a bit soon to start gloating but OH JOY !!!
I may still need to do the same further down the dam, but I feel pretty sure I found my problem and can fix it. And I still have a bag of bentonite left.
I hope this might help someone else with no tractor or way of getting big equipment into a small site, have a full pond.
