Question: Last summer, we built a slab-on-grade concrete parking lot. This winter, our finishing techniques are being blamed for damage caused by a plow during snow removal. The building supervisor is complaining about the joints that we hand-tooled. He's claiming the groover wasn't held perfectly flat, but was slanted, creating a slight ridge along the joint line. Naturally, when the plow comes through with the blade down, front wheels up, and all the pressure on the blade tip, the blade spalls off the joint edge. We don't think this is our problem. If it is, we'll be coming back after every winter to fix the spalls. What can we do to convince the building supervisor it's not our problem?