Any time a piling contractor bids a job, steps foot on the site, and starts driving a pile, there is a real risk that the indications of subsurface conditions in the geotechnical report and soils borings don't match up to what's encountered. The blow counts go way up, or the pile sinks like in quicksand. where the presumed bedrock has disappeared. The differing site conditions (DSC) clause is mandatory of federally funded projects and in most state public contract codes. This should be easy, right? Yet there is often no fight harder fought when a DSC claim is made. Why is that?