The homesteaders here a hundred years ago were barely learning about concrete and the few places I have found it, they made it only a couple inches thick (just walking on it for a few years has it all broken up). The place where I have my little metal barns today (one horse, one cow, each the size of a double garage) once had one of those big wooden barns with the mansard roof which, apparently, burned down about 50 years ago. I am still finding rusty bent nails all over that area - worked into the soil, then rain and wind brings them back up. I have picked up hundreds of them in the past 14 years. But I will be drilling (OK, augering) in an area where I have done it before, so no sweat.