The site is underlain by silty soil over highly fractured siltstone and shale of the Passaic Formation. Borehole logging and coring indicate sub-horizontal bedding plane fractures and near-vertical fractures with variable strike orientations. The average fracture aperture is 180 microns and spacing is 36 centimeters. Bedrock matrix porosity is 0.056 and organic carbon content averages 0.00074. The water table is approximately 30 feet below grade and is within the bedrock.
Targeted Environmental Media:
 Fractured Bedrock
Major Contaminants and Maximum Concentrations:
- Trichloroethene (21,400 µg/L)
- Fluid Loggings
- Flow
Comments:
Sodium bromide (NaBr) was used as a conservative tracer and provided a benchmark that could be used to calculate permanganate consumption between the injection and extraction wells.
Hydraulic conductivity tests were used to evaluate the impacts of manganese dioxide (MnO2) precipitate on bedrock permeability.
- Chemical Oxidation (In Situ)
Comments:
The saturated open intervals at the injection wells are 30 feet below grade and the extraction wells are 68 feet below grade. The extraction well is approximately 50 feet downgradient of the injection well. Injection and extraction were carried out at 1.0 gallon per minute (gpm) for a continuous 6.3-day period in March 2003. A solution of 20,000 mg/L (2 percent) potassium permanganate (KMnO4) and 10,000 mg/L (1 percent) NaBr was injected during the first 24 hours of the test. KMnO4 served as a reactive tracer and NaBr was a conservative tracer. Clean potable water was injected during days 2 to 6.3 to "chase" the tracer slug and to maintain a consistent flow field.
The pilot test results are being used to develop a plan for long-term reduction in concentrations of trichloroethene (TCE) in monitored groundwater.
KMnO4 and Br- were initially detected within 4 hours after the start of injection. The KMnO4 concentration at the extraction well peaked at 292 mg/L after 3.25 days. The concentration was 121 mg/L at the end of the 6.3-day extraction period and was 24.5 mg/L 23.7 days after the injection started. During the test, the concentration of TCE at the extraction well decreased from 21.4 mg/L to a minimum of 2.7 mg/L at 3.7 days. TCE concentrations later rebounded to within 30 percent of the pre-test concentrations within 23.7 days. The extracted mass of Br- and KMnO4 was evaluated by integration and established the fraction of the injected tracer "slug" extracted and the relative mass of permanganate consumed during the test (40 percent). The pseudo first-order oxidant half-life (190 to 200 hours) and percentage of oxidant consumed by oxidizing TCE (31 percent to 40 percent) were calculated using two independent mass-balance methods. The remaining 60 percent to 69 percent of the KMnO4 was consumed by the geologic formation.
Reference:
Gefell, Michael J.; Paul Mlodzinski; Kenneth L. Sperry; Christian Stanley; Jams R.Y. Rawson; Edward Koloddziej. 2004. Field-scale TCE oxidation in sedimentary bedrock using permanganate with bromide tracer. The Fourth International Remediation of Chlorinated and Recalcitrant Compounds Conference, Monterey, California. May 24-27.
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