LESSONS LEARNED AT THE ARGONNE PHYTOREMEDIATION SITE

Past waste disposal practices at the 317 Area of Argonne National Laboratory resulted in VOC- and tritium-contaminated groundwater. Site characterization, monitoring, and remedial actions have led to an improved understanding of the dynamics of groundwater movement and contaminant transport. One component of the remedy is a phytoremediation system installed in 1999. Over 800 hybrid willow and poplar trees have comprised the system, with hundreds installed in 25-foot boreholes through fine-grained glacial till to target a contaminated sandy aquifer. Continuous water level data from many of the site monitoring wells have led to a modification of the initial conceptual site model. Altogether, site monitoring has indicated the degree of hydraulic control provided by the trees, a subsurface infrastructure issue, unexpected directions of movement of contaminants, and the effect of drought.