Thank you CBG, CW and Tony for the ideas! Silver Searcher, if you are right, (and the google images have some that sure do resemble!) then I'm going to go back and excavate that trench. I believe there must be an elaborate system of underground tunnels holding massive amounts of Confederate gold and it's sealed with manhole covers! (Note to self: Don't forget manhole cover removal key). Seriously, I appreciate all the help.