AB, I very nearly came to grief on my property by assuming that a red hill was red clay, perfectly suitable for dam construction. Then Mike Otto showed me the error of my ways, as the red was mostly iron oxide plus sand. Despite appearances, it would never work.
I say this just to warn you that even though clay may be in your neighborhood, it might have missed you, or it may not be the right kind or in the right spot.
Your report sounds reasonably promising from what this non-expert can tell, but you won't know for sure until you bring an experienced dirt guy out with a backhoe to dig a few trenches. In my case, we did find good clay (gray white, not red) eventually down near the creek bottom, thank God.
But I've heard that a gentleman living just a couple miles from me has almost zero clay. Despite warnings, he decided to go ahead with a dam anyhow. It failed within a few years. So please PLEASE bring out a good dirt guy to check before you build!
