Jxxxx
I feel your pain
I've used bentonite also
Drained the pond re-cored my dam and compacted the bottom
It's still drain down
Lastly I orederd 300 lbs of polymer I have a source @ 2.75 per pound
The pond drained down to 3' so I tilled the polymer around the edges and most of the bottom
The remaining water in the pond I just sprinkled it in
Along with tilling in the polymer and I ordered 80 tons of Pond silt
The Pond silt was only $250 per 20 ton truck load
check your local quarry it's fine silt when they process gravel
So after 3 long years it finally looks like it's holding
Although the jury is still out I won't report success until we have a long hot summer
If you would like to private message me I will pass along my contact for the polymer
On another note I spoke to a friend who dug two ponds, he told me the first three years they filled and drain down to nothing now they're holding fine maybe I'm just a little impatient