There are two distinct release areas at the site: (1) Primary Source Area located along the loading dock and (2) Secondary Release Area located within a wetland buffer zone in the southern undeveloped portion of the property. Bedrock underlying the site is the Brunswick Shale and is highly fractured to a depth of 80 feet below ground surface. Three water-bearing depth ranges or zones are presently monitored at the Site: shallow, unconfined perched zone, a shallow bedrock aquifer, which is highly weathered, and a deep bedrock zone. Based on historical ground water elevations, an east-northeasterly ground water flow direction is evident in the perched zone and shallow bedrock aquifer. The vertical hydraulic gradient at the Site is generally downward.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
Higher concentrations of contaminants are located within the Primary Source Area and dense, nonaqueous-phase liquid (DNAPL) appears to have migrated through the bedrock fractures to locations beneath the building. In both release areas, the highest ground water concentrations are detected in the shallow bedrock aquifer, indicating that the decrease in fracturing has mitigated the downward migration of contaminants.
Major Contaminants and Maximum Concentrations:
- 1,1,1-Trichloroethane (10,000 µg/L)
- 1,1-Dichloroethane (390 µg/L)
- 1,1-Dichloroethene (3,400 µg/L)
- Chloroethane (26 µg/L)
- Fluid Loggings
- Flow
- Vertical Chemical Profiling
- Coring
Comments:
Results of bedrock coring conducted at the site showed that the red shale underlying the unconsolidated materials continued to beyond 100 feet below ground surface (bgs) at the Site. The shale was highly fractured to a depth of 80 feet bgs. The frequency of observed fractures decreased between 80 and 100 feet bgs.
- Pump and Treat
- Bioremediation (In Situ)
- Reductive Dechlorination (In Situ Bioremediation)
Comments:
A pump and treat system has been in operation since July 2001 as an interim remedial measure. The system has been effective in minimizing further off-site migration of contaminants.
A combined abiotic/biotic field pilot study was performed at the industrial site, which had high concentrations of chlorinated solvents in a fractured bedrock ground water system. The pilot study was implemented within the Secondary Source Area and consisted of zero-valent iron (ZVI) powder and an emulsified vegetable oil amendment, which was a blend of emulsified soybean oil and sodium lactate. The contamination in the Secondary Source Area was relatively localized. Two nearby ground water wells, one an extraction well and one a monitoring well, were converted into injection wells for the pilot study. The ZVI/oil injection solution was pumped into the injection wells at pressures ranging from 25 to 50 pounds per square inch (psi). A total of 300 pounds of ZVI and 1,500 gallons of emulsified vegetable oil amendment were injected into the two wells over a two day period. A monitoring well was also used in the pilot study and was located approximately 60 feet down downgradient from the injections wells. Ground water monitoring was performed one month prior to and 13 months subsequent to the pilot study injection.
The field pilot study injection of the ZVI/oil solution proved successful in quickly remediating a bedrock aquifer contaminated with (1,1,1-trichloroethane (TCA) and degredation products. The ZVI catalyzes rapid abiotic degradation of TCA and the degradation products, while the emulsified vegetable oil supports long-term biological reductive dechlorination by Dehalococcides ethenogenes and TCA-degrading microorganisms. Ground water monitoring for 13 months after the injection indicated that TCA concentrations decreased from 10,000ug/L to below detection limits within seven months and continued to be below detection limits more than one year after the pilot study.
Clean up goals were not specifically stated in the publication.
Ground water 1,1,1-trichloroethane (TCA) contamination levels were reduced to below detection limits within seven months of the beginning of the pilot study and remained there more than one year after the conclusion of the study.
The presence of 1,1,1-trichloroethane (TCA) does not appear to affect the Dehalococcides ethenogenes.
Reference Chu, P., Mateo, J., Fogel, S., Freim, J., Blackmore, C., Newman, W., Crisman, D. 2005. Rapid In Situ Dechlorination of Solvents by Abiotic and Biotic Mechanisms. Presented in Proceedings of the Eigth International In Situ and On-Site Bioremediation Symposium, Baltimore, MD. www.battelle.orgbookstore
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