It’s difficult to explain why we sort into constituent parts without using technical terms but essentially where soils are suitable for washing, contaminants can be isolated in to one of the constituent parts therefore if you can isolate and remove that part, the remaining materials are not contaminated. The majority of contaminants are usually found in the fines, leaving you with clean sand and gravel following washing, materials easy to re-use or dispose of.
Soil washing is ideal for reducing disposal volumes, although the resulting contaminated materials can often be ‘treated’ using bioremediation or chemox for example.
