For decades, the EVS Applied Geosciences and Environmental Management program has been improving methods for characterizing and restoring environmental sites contaminated with carbon tetrachloride. A key to our streamlined site characterization process is extensive use of cone penetrometer technology, with customized sampling and drilling tools, to minimize intrusiveness and the amount of hazardous waste generated. We have also improved analytical methods so that we can rapidly detect lower concentrations of contaminants and have developed methods for integrating accumulating results to direct the next steps of our investigations.
Our remediation goal is to clean up soil and groundwater by using site-appropriate, efficient technologies that ultimately minimize emissions and incorporate beneficial reuse of resources. We have applied a number of emerging treatment technologies where site conditions are appropriate. The innovative methods used include spray irrigation treatment of extracted groundwater; a large-scale groundwater treatment system integrating phytoremediation, engineered wetlands, and spray irrigation; a combined soil vapor extraction-air sparging system in large-diameter boreholes; and enhanced biodegradation in the vadose zone via subsurface injection of zero-valent iron.
Extensive monitoring of our remediation projects has generated a body of data to support detailed evaluations of the technologies. Our life-cycle cost analyses, projected over 15 years of treatment, demonstrate significant savings in greenhouse gas emissions, energy, and monetary costs. These savings are realized by eliminating processes, materials, wastes, and operating time. Moreover, the “green” technologies have resulted in reuse of contaminated water and soil, enhancement of wildlife habitats, and wetlands restoration, in addition to site cleanup.
Our work in Nebraska, Kansas, and Missouri is supported by the Commodity Credit Corporation of the U.S. Department of Agriculture. We have characterized scores of former federal grain storage facilities where carbon tetrachloride was used as a pesticide and have implemented successful remediation projects at many of these sites.