All was well - or so it seemed. The water cleared such that the pond bottom can be seen.
Then something went wrong. After the water level remaining steady for weeks, it suddenly dropped to a lower level and steadied again. Speculating that indicated a leak around the edges somewhere, more bentonite was spread along the banks. But that did not stop the leakage or seepage. And the water level dropped even further. And further.
Chatting with our bentonite supplier, he said that - in his experience - a second application was needed in some of test ponds he'd built, near his quarry. He said that he 'threw' the second application out onto the water surface, using his digger.
From his comments, I speculate that the layer of bentonite we put on the pond bed had become saturated and the water is slowly oozing / seeping through, over the entire pond bed area. If that's correct, then I doubt that a polymer application would solve it.
So it looks like a second bentonite application, broadcast across the surface, is going to be necessary. Bugger!
