I tried 12 tons or bentonite that didn't work
My problem was that I never payed much attention to the bottom of the pond
Also my neighbor who is an excellent excavator operator but knew nothing about building ponds did not core half of the dam when I left home alone
I cored the first half
I knew right away it was not holding, it would get a little water then drain right out
So I tried the bentonite it helped a little but would still not hold past half full
A few weekends it filled and ran out the overflow pipe but would drop 14" a week until the halfway mark
I had a good idea what the problem was from the start
1) the dam was not cored correctly
2) the bottom in one section was not cleared or one large stump and a rock formation
3) the bottom was not compacted
It turns out there was an underground stream where the water was running through
It was finding its way through the large stump and rocks and running under the dam
My solution was to rent the excavator and dozer again with the addition of a sheep's foot compactor
1) I cored the front of the dam down 15' down filled and compacted
2) ripped out that stump that bothered me from day one
3) ripped out all the rock around the stump
4) ripped up the whole bottom removing all large rocks
5) core trenched around the whole pond
6) compacted the hell out of it
I knew right away it was holding when I got a foot of water and it held
I redid it in September and it's now about 3/4 full and holding
With all the snow we are having it's going to be a great spring
One last thing I believe I achieved was
I core trenched the top of the pond where the water runoff enters the pond,
By doing that I believe I created an under ground dam forcing the water up and into the pond instead of running under .......
So my advice is to follow the advice from all the knowledgeable experts on the forum
