The chlorinated solvent tetrachloroethylene or perchloroethylene (PCE) was released in a dry cleaning facility located in the basement of a large hotel. Although several monitoring wells were drilled/installed in the hotel basement near the dry cleaning facility, the areal extent and center of mass of the PCE plume (and daughter product plumes - TCE, DCE, etc.) were not fully delineated. The primary tasks included determining the component concentrations, delineating the areal extents of the PCE, TCE and DCE plumes, and direction of contaminant migration.

Approach: A soil vapor survey was conducted, using ETI's manually operated probing system, in and around the dry cleaning facility located in the hotel basement. Samples were collected on a closely spaced sampling grid from depths of between one and four feet below the concrete floor of the hotel basement. All vapor samples were analyzed for chlorinated hydrocarbons including PCE, TCE and DCE. Samples were also analyzed for methane, ethane and ethylene, since these compounds are degradation products of chlorinated solvents and can be very helpful in determining the overall extent of the impact due to the release of chlorinated solvents

Results:  Hydrocarbon constituent plume maps were constructed to illustrate the areal distribution of chlorinated hydrocarbons (PCE, TCE, DCE) and other associated degradation products (methane, ethane and ethylene) utilizing the results of the soil vapor analyses. The chlorinated hydrocarbon constituent maps (PCE, TCE and DCE) show slightly different plume geometries and locations of the highest component concentrations. The center of mass for the parent compound PCE and the daughter compounds (TCE and DCE) are not coincident. It is apparent that biodegradation occurred during the migration of the PCE in the shallow groundwater. In addition, the random placement of the monitoring wells was not adequate in delineating the areal extent, nor highest concentrations of the respective contaminants in the plumes.

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