Is there a geotechnical report for the site? Borings are the only thing I know of that might hold up in a court. I take it this is a private bldg.where the owner played construction manager?... If you do use GPR, back it up with borings around the bldg footprint and inside if possible.I'm...
As long as the required testing has been performed properly, and the geotech. recommendations have been followed. Why is there a concern? Building is past any problem being solved now. How much fill was placed to require GPR?