Metallic, masonry, and other solid debris that may be contaminated with hazardous chemicals litter numerous hazardous waste sites in the United States. Polychlorinated biphenyls (PCB's), pesticides, lead or other metals are some of the contaminants of concern. In some cases cleanup standards have been established (e.g., 10 micrograms PCB's/100 sq cm for surfaces to which humans may be frequently exposed). Decontaminated debris could be either returned to the site as 'clean' fill, or, in the case of the metallic debris, sold to a metal smelter. The project involves the development and demonstration of a technology specifically for performing on-site decontamination of debris. Both bench-scale and pilot-scale versions of a debris washing system (DWS) have been designed, constructed and demonstrated. The DWS entails the application of an aqueous solution during a high-pressure spray cycle, followed by turbulent wash and rinse cycles. The aqueous cleaning solution is recovered and reconditioned for reuse concurrently with the debris-cleaning process, which minimizes the quantity of process water required to clean the debris. (Copyright (c) 1991, Air and Waste Management Association.)