The treatment zone encompassed 90 feet below ground surface (bgs). The top 75 feet bgs consists of weathered bedrock and saprolite and the bottom 15 feet bgs consists of fractured gneiss. The water table occurs at 55 feet bgs.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
Major Contaminants and Maximum Concentrations:
- Trichloroethene (1,100,000 µg/L)
- Other
Comments:
No site characterization technologies were identified within the references abstract.
- Thermal Treatment (In Situ)
Comments:
Thermal Conduction Heating (TCH), also known as In-Situ thermal Desorption (ITSD), was used to treat TCE. The remediation system consisted of using TCH to heat the subsurface and vacuuming the organic chemicals. Electrically powered heaters were installed at regular intervals throughout the treatment zone and the heat primarily moved into the inter-well regions by thermal conduction. Though the primary objective was to remove TCE from the top 75 feet bgs, the treatment zone extended to 90 feet bgs in order to create a hot floor. In addition, groundwater extraction was used to create an upward hydraulic gradient between the bedrock and unconsolidated soils. This hydraulic gradient provided additional protection against any DNAPL that may have mobilized during heating.
The cleanup goal was to achieve an 95% upper confidence level (UCL) of the mean TCE soil concentration less than 60 µg/kg.
The post remediation 95% UCL for the mean TCE soil concentration was 17 µg/kg, with groundwater concentration less than 5 µg/L.
Thorough contaminant removal was seen based on soil samples from within the treatment zone.
References:
LaChance, John, Gorm Heron, and Ralph Baker. Abstract of Use of Thermal Conduction Heating for the Remediation of DNAPL in Fractured Bedrock, Platform Abstract Session C5. Presented at the Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds. Monterey, CA. May 19-22, 2008.
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