Well I removed all the trees and roots and began core trench. At about 15' we hit sand/water. We were able to dig through the sand seam back down to clay. We are trucking out all of the sand that's close to the dam and although it will prolong the project I think this is the right thing to do.

Does anyone have any insight on this? Is there anything I should know before I dig the core and fill it with clay? I will get up some more recent pics.