Always ask the supplier where the fill is coming from and what activities were conducted at the site. Check whether any activity may have caused contamination. Ask for the site address and consider inspecting the site prior to accepting the fill. During the inspection make sure the fill does not contain any other wastes such as bricks, concrete, wood, asbestos or plastic. Also check the fill for staining, discolouration or odour.
If you don't know where the fill is from, don't take it.