Groundwater supplies throughout the United States are threatened by migration of contaminants from numerous sources including solid, chemical and hazardous waste sites. Complete isolation of these sources and their corresponding high concentration migrating plumes is a major step in mitigating the danger of groundwater contamination and is often a cost-effective step in the cleanup process.The “Block Displacement” technique has been developed for complete isolation of large tracks of contaminated ground. A full-scale demonstration was recently conducted on a 50,000 ft3 block of unconsolidated soil. The technique places an impermeable barrier around and beneath the contaminated zone. In the process, the ground is physically displaced upward by multiple well injection of a barrier material in a slurry state.Applicability assessment requires a vigorous geotechnical investigation including monitoring the propagation of a separation from a single prenotched test well at the planned bottom barrier depth.