Soil washing works primarily on the basis of volume reduction and the removal of the portions of the soil matrix which contains the most concentrated concentrations of contamination. Soil washing accurately separates different fractions of usually granular soils and if designed and operated efficiently can enable the most impacted materials to be recovered in either aqueous solution or in the form of a very condensed solid "filter cake", which can then either be treated via an alternative technology or disposed of off-site.

Soil washing is particularly beneficial when the source soils contain a heavily impacted fraction, usually silts and sand which can be easily stripped from the bulk matrix to enable overall contaminant mass removal.