Some soils may be contaminated because of old wastes. In pre-purchase inspection, the inspector will be on the lookout for hydrocarbon odors or other visual clues. Soils that have been contaminated before you become a homeowner may be a "hidden defect" unless there are visible signs. Discover the main sources of contaminants that can be found in residential areas inhabited in this article by LaPresse.ca (French only): And if the land was contaminated? Good reading!