Prefabricated Vertical Drains for Enhanced In Situ Remediation

Prefabricated vertical drains (PVDs), also known as wick or strip drains, commonly used to accelerate consolidation of fine-grained soils and sludges, have been successfully demonstrated for enhancing in situ remediation of contaminated soils and groundwater. Over the last decade, the technology basis was developed for using PVDs to accelerate in situ flushing, i.e., removal of contaminants below the groundwater table. During the last five years, the basis for using PVDs to enhance soil vapor extraction systems, i.e., removal of contaminated soil gas in the vadose zone was developed. Both of these geosynthetic applications have been field-demonstrated on a limited basis. The first at an abandoned TCE evaporation pond at a U.S. Department of Energy processing plant and the second at a municipal solid waste landfill experiencing subsurface lateral migration of methane gas. The PVD-enhanced remediation technologies have yet to find wide acceptance and utilization. Perhaps if several remaining issues are resolved and additional, well-instrumented field demonstrations are performed with results implemented in a design manual, consultants, remediation contractors and regulatory agencies will begin to include and utilize these technologies among their remediation options. In this paper we present an overview of the PVD-remediations technologies, a brief description of some past field demonstrations and our thoughts on research/development issues necessary to further the use of this technology.