The concept of reducing soil contamination through the use of soil washing and particle size separation is based on the finding that most contaminants tend to bind preferentially to clay, silt, and organic soil particles. In the washing process, the fine clay and silt particles are separated from the coarser sand and gravel soil particles. The separated fines and contaminants are dewatered into a dry filter cake suitable for off-site disposal. Additional treatment of the sand and gravel fractions maybe incorporated into the process as needed. The cleaned sand and gravel fraction can be returned to the site.