Following is a question Initiatives received from a reader.
Question:	I have read your articles on viscous liquid barriers and freeze walls. Wouldn't a conventional soil-bentonite slurry cutoff wall be cheaper when considering long-term operation costs? Aiman Naguib Geo-Con, Inc. Denton, Texas
Answer:	Frozen soil barriers may be the containment method of choice when the barrier is expected to be maintained only until a remediation plan is selected. When the decision to remediate is made, the frozen barrier is removed by simply allowing it to thaw. The Innovative Technology Summary Report, or ITSR, on Frozen Soil Barrier Technology states, "Comparison with other technologies is difficult because of the unique aspects of ground-freezing technology, including complete containment and removability. In addition, ground freezing incurs additional energy, operation, and maintenance costs over time that other containment technologies do not. However, it appears that this technology can be effectively applied in fine-grained, saturated soils for complete containment applications of relatively moderate durations where future remedial action of the contaminant source and subsequent barrier removal are desired." The Office of Science and Technology maintains a Web site for accessing its ITSRs, which compile engineering data for selected OST environmental technologies. These reports can be accessed at http://em-50.em.doe.gov.