Groundwater contamination from tetrachloroethene (PCE) and daughter products, discovered at an electronic components manufacturing facility in west central Florida, had shown little change resulting from several years of operation of a groundwater extraction/treatment system. Analytical results from one monitoring well near the center of the dissolved plume were consistently in the concentration range that suggested the presence of residual non-aqueous phase liquid (NAPL), although none was ever encountered in the course of assessment sampling. Additionally, geochemical conditions were not optimal for reductive dechlorination, possibly due to operation of the groundwater extraction system. To expedite the attainment of specific groundwater cleanup target levels (GCTLs), an interim remedial action plan was developed to meet the following objectives: ? Removal of the potential residual NAPL through excavation of a minimum quantity of soil in the vicinity of the “hot” well, ? Addition of an alternative substrate during backfilling to augment the existing conditions through a one-time substrate addition to provide a more reducing environment, without the installation of a substrate injection system, and ? To attain GCTLs through monitored natural attenuation within five years. This paper presents the results of this interim remedial action, including comparison of groundwater contaminant concentration rates of change before and after the interim action, methods employed, overall project success, and relative costs associated with this approach.
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