A demonstration of the International Waste Technologies (IWT) process utilizing the Geo-Con, Inc., deep-soil-mixing equipment occurred in April 1988 at the site of a General Electric Co., electric service shop in Hialeah, FL where the soil contained polychlorinated biphenyls (PCBs) and localized concentrations of volatile organics and heavy metal contaminants. The demonstrated process mixed the contaminated soil in-situ with a mixture of a proprietary additive, called HWT-20, and water. The technical criteria used to evaluate the effectiveness of the IWT process were contaminant mobility, based on leaching and permeability tests; and the potential integrity of solidified soils, based on measurements of physical and microstructural properties. The performance of the Geo-Con deep-soil-mixing equipment was also evaluated. The process did appear to immobile PCBs. However, because of very low PCB concentrations in the leachates, caused in part by the low concentrations of PCBs in the untreated and treated soils, absolute confirmation of PCB immobilization in the SITE project was not possible. The cost per ton of treating contaminated soil under the demonstration test conditions was determined at approximately $194.