The site consists of low-permeability glacial till and fractured bedrock. The depth to water varies, but remains generally from 10 to 20 feet below ground surface (bgs). The ground water shows slow movement, at less than 15 feet per year. Geologic conditions at the site are categorized as glaciated New England ground moraine terrain, with soils consisting of up to 10 feet of fill and disturbed materials overlying approximately 50 feet of hard till. Below the hard (basal) till are fractured schist and gneiss bedrock.
Targeted Environmental Media:
 Fractured Bedrock
Information not provided by sources sited.
Major Contaminants and Maximum Concentrations:
- Trichloroethene (0 µg/L)
- 1,1-Dichloroethene (0 µg/L)
- 1,1-Dichloroethane (0 µg/L)
No technologies selected.
- Chemical Oxidation (In Situ)
- Pump and Treat
Comments:
Pilot-scale studies were completed in October 1997 and again in 1998. In October 1997, 6,500 gallons of 350-milligrams per liter (mg/L) permanganate solution was fed by gravity into one deactivated pump well. Pumping wells surrounded the inactive well where the application took place to provide hydraulic capture and to allow measurements. Contaminant concentrations decreased by 30 percent after the injection. In 1998, a larger pilot-scale application was completed using 48,000 gallons of 1 percent permanganate solution. The solution was pumped into nine soil vapor extraction wells and 11 pumping wells using a low-pressure manifold. Results of the 1998 test showed reductions in the concentrations of total iron, with an overall contaminant reduction of 30 to 40 percent over a 3-month period.
Further pilot tests were completed in 1999 and 2000 in pumping and monitoring wells completed in the overburden and upper fractured bedrock aquifers. In 1999, 26,000 pounds of 2 percent potassium permanganate was used, as well as 3,000 pounds of sodium permanganate. In 2000, 4,000 pounds of potassium permanganate and 6,600 pounds of sodium permanganate were used. Three pumping wells were used as the points of injection in both the 1999 and 2000 applications.
The goal in 1999 was to disperse permanganate across the site using only three downgradient pumping wells to maintain hydraulic control. The goal in 2000 was to use a small quantity of permanganate to target hot spots and areas in the vicinity of a nearby stream to monitor the potential for enhanced migration, preferential flow, and impacts to shallow aquifers.
The results of the 1999 testing showed reductions in the concentration of volatile organic compounds (VOCs) to non-detectable levels. VOC concentrations in the wells located outside of the treated area showed no impact from the oxidant, however. A decrease was also shown in the chlorinated ethenes and non-chlorinated VOCs in both the bedrock and overburden aquifers. Results in the 2000 test showed that concentrations of VOCs in the pumping and monitoring wells continued to decrease. Concentrations for the chlorinated ethenes remained unchanged, and all the readily oxidized compounds were oxidized, leaving only the recalcitrant compounds.
As the program continued, the concentrations of oxidizable constituents such as trichloroethene (TCE) decreased, while the non-oxidizable compounds such as dichloroethene (DCE) and dichloroethane (DCA) remained stable. A biological reductive dechlorination process would be tested instead and would be altered to react to the site limitations and setbacks found from the permanganate tests.
References: Pac, Tim, Richard Lewis, and Terry Connelly. Sequential Implementation Of In Situ Chemical Oxidation and Reductive Dechlorination. Paper 5A-11. Fourth International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, California). May 2004.
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