Site includes shallow, gravelly, sandy zone, peat, and deep, silty sand layers. Five stratigraphic zones are present at the site: a gravelly sand zone (6 to 13 feet below ground surface [bgs]), a peat zone (12 to 14 feet bgs), a fine sandy-silt zone (14 to 26 feet bgs), a basal till zone (26 to 30 feet bgs), and a fractured bedrock zone (lower than 30 feet bgs). The upper three zones were targeted by this demonstration. Groundwater is present at approximately 3 feet bgs and has a horizontal gradient of 0.04 feet per foot. DNAPL is present at 23 to 25 feet bgs and occurs just above the basal till zone.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
27,000 cubic feet of soil was treated at the site. The contaminant source area is approximately 80 feet long by 50 feet wide by 26 feet deep.
Major Contaminants and Maximum Concentrations:
- Tetrachloroethene (75,259 µg/L)
- Trichloroethene (1,314 µg/L)
- cis-1,2-Dichloroethene (6,904 µg/L)
- Vinyl chloride (1,677 µg/L)
- 1,1,1-Trichloroethane (Not provided)
- 1,1-Dichloroethane (Not provided)
No technologies selected.
- Chemical Oxidation (In Situ)
Comments:
The pilot study lasted from March 2005 to May 2006. Three well clusters were located within the 1,200-square foot treatment area. Each cluster consisted of three 1-inch wells, and each was screened in one of the three stratigraphic zones. The clusters were estimated to have radii of influence of 10 feet and were placed 18 feet apart, allowing for overlapping areas of influence. An initial injection occurred in June 2005 and consisted of 5,524 gallons at a concentration of 25 grams per liter (g/L) (1,758 pounds of potassium permanganate). A subsequent injection was necessary due to failed seals on two of the three well clusters. These wells were replaced with 2-inch diameter wells. The second injection occurred in October 2005 and included 9,365 gallons at a concentration of 36 to 40 g/L (1,929 pounds of potassium permanganate). In total, approximately 15,000 gallons (containing nearly 4,000 pounds of potassium permanganate) were injected, of which, half was injected into the deeper sandy-silt zone, approximately 40 percent was injected into the peat layer, and the remaining 10 percent was injected into the upper gravelly-sand zone.
The objective for the soil phase was to reduce PCE, TCE, cDCE, and vinyl chloride (VC) concentrations by 90 percent. The main objective for the ground water phase was to reduce concentrations of the specified VOCs below 0.5 percent of their respective solubility limits (i.e., for PCE - 750 µg/L, TCE - 5,500 µg/L, and cDCE - 17,500 µg/L).
Soil and groundwater monitoring were conducted to assess treatment performance. Soil samples were collected in May 2005 and March 2006 (before and after treatment). Based on all detected values, PCE is the only contaminant that showed a relevant decrease in average concentrations (63.5 percent decrease) across the three stratigraphic zones. Concentrations of PCE and TCE decreased in both the peat and deeper zones: in the peat zone, PCE decreased by 96 percent and TCE by 92 percent, and in the deeper zone, PCE decreased by 89 percent and TCE by 98 percent.
Groundwater samples were collected in June, September and December 2005 and February and May 2006 (before, during, and after treatment). Based on averages of all sampling data, PCE showed a 27 percent reduction to slightly below its goal; TCE and cis-DCE showed more significant reductions at 51 and 58 percents, respectively. Based on averages of the three groundwater zones: samples from the shallow zone showed decreases for PCE, TCE, and cis-DCE; samples in the peat zone showed increases in PCE and TCE, and decreases in cis-DCE; and samples from the deeper zone showed no appreciable change for either PCE, TCE, or cis-DCE.
In addition, permanganate was observed in all deep wells indicating good presence and persistence in the deep zone. In the deeper and shallow zones, permanganate was only observed once suggesting possible exhaustion of the oxidant by high soil oxidant demand.
References:
U.S. Environmental Protection Agency - National Risk Management Research Laboratory (NRMRL). May 2007. Xpert Design and Diagnostics (XDD) In Situ Chemical Oxidation Process Using Potassium Permanganate (KMnO4) Innovative Technology Evaluation Report. EPA540R-07005. Available at: http:www.epa.govORDNRMRLpubs540r07005540r07005.pdf (date accessed: 111307)
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