The source area geology consists of glacial till and fill materials. The wetland consists of low-permeability soils overlying more permeable stratified drift. Bedrock beneath the plume is composed of a fractured layer with weathered gneiss set on top of competent rock. Ground water was moderate to slightly oxidizing.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
The plume extends over a 14-acre area.
Major Contaminants and Maximum Concentrations:
- Trichloroethene (1 µg/L)
- Other (Bromide conservative tracer)
- Bioremediation (In Situ)
- Reductive Dechlorination (In Situ Bioremediation)
Comments:
Three separate pilot tests were conducted in different areas of the site by injecting a carbon source into the saturated aquifer. A mixture of potable water, emulsified vegetable oil, lactate, vitamin B12, and bromide was injected into the source zone area (pilot test 1) and within the plume on the edge of the wetland (pilot test 2). Hydrogen release compound, soluble lactate, and bromide were injected at a second location on the edge of the wetland (pilot test 3). Performance results were evaluated by monitoring the concentrations of volatile organic compounds and geochemical and microbial parameters.
The goals of the project were to evaluate the feasibility of biologically mediated reductive dechlorination as a remediation alternative and to collect site-specific design information for bioremediation.
Results varied by location. Further details may be obtained from the site contact. Cis-1,2-dichloroethylene and vinyl chloride were present at each of the testing areas; however, the rate of biodegradation for the wetland test areas was much higher than in the source test area. The distribution of the injected substrate differed by area. The pilot tests were optimized using modifications such as acid neutralization and bioaugmentation.
Differences in aqueous chemistry during the tests and geologic conditions were potential reasons for the differing test results at the three pilot test areas.
References: Hellerich, Lucas A., John Albrecht, and Dave Hart. Bioremediation Field Pilot Studies to Address DNAPL TCE in a Complex Geologic Setting. The Ninth International In Situ and On-Site Bioremediation Symposium. May 7 - 10, 2007. Baltimore, Maryland.
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