Implementation Issues

It has been estimated that as many as 1,000 Department of Defense (DoD) cleanup sites worldwide could utilize this technology, saving hundreds of millions of dollars. Current pump-and-treat technologies are costly and not always completely effective, and phytoremediation may provide a low-cost, low-maintenance technology for long-term treatment of contaminated sites. In addition, it is becoming more evident that communities where hazardous material releases have occurred favor remediation via vegetation for its aesthetic effects. The total estimated cost for groundwater TCE remediation over a ten-year period is $500 to $660 thousand; however, the efficiency has not been verified over this time period in the current field demonstration. The predominant costs include analytical services, labor, and a supplemental irrigation system for the first two years. Start-up, material, and maintenance costs are low compared to other remediation technologies.

The results indicate that phreatophytic trees can be used, under appropriate conditions, to reduce the mass fluxes of groundwater and TCE flowing beneath a tree plantation. These conditions include a depth to groundwater that tree roots can reach and a water balance that favors the trees' use of groundwater to supply some of their evapotranspiration demands. Properties of the contaminant are also important. While the trees used in this study are relatively fast-growing, it may take two to three growing seasons for roots to reach groundwater and up to ten years for canopy closure and optimum efficiency to occur. Supplemental irrigation may be required during the first one to two years to supply adequate water before their roots reach groundwater. (Project Completed - 2004)