Great post Joe. I can
feel your anxiety! Relax, it always feels better when it quits hurting.
The soil near the creek bed may not representative of what you you will find deeper. Of course there is always a chance of hitting an old, meandering creek bed at different depths, but I wouldn't worry about it. Sand or gravel deposits probably won't be thick in such a widespread clay area as yours.
As much clay as you have, you won't have any problems keying your dam or packing in any sandy areas you happen to uncover.
Good luck, and keep us informed!
