The facility is located within the Paris Mountain thrust sheet of the Inner Piedmont belt of the Piedmont Physiographic Province of South Carolina. The bedrock varies in location from 4 feet below ground surface (bgs) to more than 70 feet bgs. Bedrock ranges from 55 feet bgs to more than 70 feet bls within the source zone, and the water table is at approximately 15 feet bgs.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
Information was not identified by the source sited.
Major Contaminants and Maximum Concentrations:
- Polychlorinated biphenyls (PCBs) (4 µg/L)
- Polychlorinated biphenyls (PCBs) (4 µg/L)
No technologies selected.
- Chemical Oxidation (In Situ)
Comments:
Dowtherm®A is a heat transfer product composed of 1,1-biphenyl and biphenyl ether. In December 1999, the source area at the former location of a recirculation pump was removed by excavation of contaminated soil to the underlying rock. Fentons reagent was used to oxidize the contaminants using ferrous sulfate solution along with a 7.5 percent hydrogen peroxide solution. The original outcome showed significant decreases in concentrations of 1,1biphenyl and biphenyl ether in the soil at the interface of bedrock. However, long-term results showed that Fentons reagent failed to completely oxidize the Dowtherm® A. Because of the high cost of the reagent and the unfavorable results, Fentons reagent is no longer being considered as a remedial agent for the site. Oxygen Release Compound (ORC®) has been implemented as an alternative remedy.
A Phase I injection using ORC ® was completed on April 2001. ORC® was injected directly into five bedrock monitoring wells. Ground water from four of the five wells met the cleanup criteria in less than 8 months after injection. To address remaining contamination additional ORC® was implemented in 2001. ORC® socks were installed on January 23, 2002; the socks, however, needed to be changed monthly, as described by the manufacturer. A second phase of ORC® (as a slurry) was injected into six monitoring wells in May 2002. The results of the second injection showed that ground water from five of the six wells were below cleanup goals within 15 months of the injection.
A pilot study was conducted to evaluate whether ORC® could be used to remediate contaminants (specifically Dowtherm® A) in a bedrock aquifer.
Data from the area where the ORC® socks were installed showed a 68 percent reduction in the concentration of 1,1-biphenyl and a 63 percent reduction in the concentration of biphenyl ether. Ground water from four of the five wells injected during the Phase I ORC® injection met the cleanup criteria in less than 8 months after injection. The results of the second phase injection showed that ground water from five of the six wells were below cleanup goals within 15 months of the injection.
Although the technology was successful in reducing concentrations, maintenance of the remedial application is not cost effective. ORC® socks were determined as impractical because of the need to replace them each month. Injection of ORC® slurry into the bedrock aquifer also was found not to be a viable option because of the strong possibility that the ORC would clog the bedrock fractures.
References: Rhine, Elizabeth M. In Situ Bioremediation of Dowtherm® in Bedrock Aquifer Using Oxiclean®. 2004. Paper 2E-04. The Fourth International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, California). May 24-27.
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