Do you know for certain how deep the muck is? The reason I ask is I am currently cleaning out a couple areas that are probably 2 to 3 times the size of what you are talking about but I have dirt coming out my nose because when we started digging with the track hoe they didnt find the original clay until 6-8 feet down...

Where are you located? I am between bunker hill and staunton, if it would help you to see what came out of mine and how huge the dirt pile I have is let me know.

My pond renovation thread here