Leo:
Here's a link to my pond renovation.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Main=12914&Number=151396#Post151396 In some of the pictures you can see some of the yellow sand that I'm talking about. I live in the same county, and have very similar soil types as the winterkilled pond. I dug my pond down to 22' deep, and ran into the first thin layer of clay at 12' depth. The winterkilled pond wasn't dug that deep, I'm estimating 10' below the orig. existing soil level, so if that clay is there, it was never reached.
In my pond, once that 12" thick layer of sand/clay was passed, it turned to sandy loam again. At about the 15' depth mark, we hit another layer of gravel, which slowly turned to solid grey clay at about the 19' level. Unfortunately, there wasn't enough clay dug out of my pond to line the whole thing.
I have fluctuating water levels in my pond too, but I think my pond hasn't winterkilled for one reason:
I have a larger volume of water in the pond, and it provides a bigger "bank" of D.O. for the fish during the winter if I don't aerate the pond during the winter (which I have done with no winterkill issues). I'm sure that I have a higher biomass of fish in my pond than the winterkilled pond in question if you just figure on pounds of fish per surface acreage. But, since my pond has 2x to 3x more water volume, that gives me more leeway in regards to available O2 for the fish if you calculate the pounds of fish per gallon of water.
Last year, my pond shrunk to somewhere around 1/2ac to 5/8ac due to the lack of precipitation and the resulting drop in ground water level.
At that low water level, I still had 11' to 12' of water in the deepest part of the pond, and no winterkill even without aeration.
Here's what it looked like a few months later after we had some water come down:
The water level came up roughly 65" from the low water mark. The stick that you see out from the tree in the first picture is a pipe with a 72" aluminum "yardstick" on it. It is compeltely out of the water by about 5" in the first picture. The water level on the stick was 59 3/4" at the time of the last picture.
