Dribble Creek, I'm not using the shell/gravel for the dam at all. I am taking it out for roads and cow lot.
Brettski, I haven't tried that test but I have tried other tests like Mike Otto's test to put balls in water and the black topsoil (called Houston clay by the way) passes the test but I don't think it would hold water very good. The soil right above the yellow clay is a yellowish brown color that has little gravel or sand or anything else and is hell to dig. It stopps the dozer because it doesn't break and the dozer blade creates a smooth cut that shines in the sun. It might work for a dam, might be too much clay and crack or whatever. There are a lot of different soils in the same area that confuse me but I am keeping to what I know worked with the existing pond to be safe.