How do you verify that your suppliers actually supply you with what for which they bill you? Make sure to get your old brake pads.
“Caterpillar Probed for Dumping,” Wall Street Journal, November 22, 2013 B1 http://on.wsj.com/1g3Izpk Allegations that replaced parts were dumped at sea to avoid discovery.
Oh, and by the way: the Clean Water Act prohibits the unpermitted discharge of a pollutant into the waters of the US. Did you have a permit? Does your contractor? Have you arranged for the illegal disposal?
Where’s the information in this vignette? Where are the controls?