Subsurface materials on the site consist of fill, natural unconsolidated materials, saprolite, and bedrock. The bedrock is found at depths ranging from less than 15 feet below ground surface in some areas to greater than 25 feet below ground surface at areas of higher elevation. Within the higher elevations of bedrock, groundwater was found in confined conditions. The fractured bedrock groundwater flow system has an undetermined thickness but the flow is generally towards the main regional surface water body called Paint Branch. The average saprolite seepage velocity was calculated as 5.4 feet per day; the average bedrock seepage velocity was calculated to be 0.48 feet per day.
Targeted Environmental Media:
 Fractured Bedrock
The plume is approximately 100 feet in diameter and has an estimated surface area of approximately 8,000 square feet. The plume has an average thickness of 50 feet and extends from the groundwater table located at approximately 40 feet below ground surface to approximately 90 feet below ground surface. The plume seems to originate from the vicinity of Building 613.
Major Contaminants and Maximum Concentrations:
- Tetrachloroethene (34 µg/L)
- Trichloroethene (0 µg/L)
- cis-1,2-Dichloroethene (0 µg/L)
- Other
Comments:
Values for seepage velocity within the saprolite and bedrock were developed using measured slug test data and the pneumatic surface site map.
- Fracturing
- Bioremediation (In Situ)
- Reductive Dechlorination (In Situ Bioremediation)
Comments:
From May 7 through June 3, 2007, pneumatic fracturing was performed to increase subsurface permeability and was followed by the injection of emulsified oil substrate into forty-five boreholes. Pneumatic fracturing pressures ranged from 60 to 700 pounds per square inch. Within a 60,000 square foot treatment area, approximately 10,440 pounds of 60% oil substrate was injected into the boreholes with a substrate injection pressure range of 35 to 260 pounds per square inch. Following injection of the emulsion, 57 gallons of chase water was injected. Monitoring of the substrate distribution, persistence and treatment effectiveness took place via five existing monitoring wells located within 30 feet of the injection points.
PCE 5 µg/L
TCE 5 µg/L
Cis-1,2-DCE 70 µg/L
Immediately following injection, visual inspection of groundwater monitoring samples and measurement of elevated total organic carbon confirmed initial substrate distribution. Within six months of injection, samples for all treatment-area wells indicated that PCE concentrations had decreased below 5 mg/L. Notable rebound in contaminant concentrations was seen in two of the monitoring wells in the treatment zone (one was located 40 feet downgradient and the other was 20 feet cross gradient). At the monitoring well located closest to the creek, data showed a steady decline in PCE concentrations and moderate increases in PCE daughter products which implies that PCE contamination is not migrating.
References:
Steckler, David, Steven G. Kawchak, and Michael Liskowitz. Enhanced Reductive Dechlorination Using a Vegetable Oil Emulsion in a Fractured Bedrock Aquifer, Platform Abstract Session A4. Presented at the Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds. Monterey, CA. May 19-22, 2008.
EPA. 2005. Record of Decision: USN Naval Surface Warfare CTR-White Oak.
http:www.epa.govsuperfundsitesrodsfulltextr2006030001473.pdf
EPA. 2007. Final Five-Year Review For OU 2 & OU 3 (Apple Orchard Landfill and Surface and Groundwater), Site 4 (Chemical Burial Area), Site 513 (Open Bum and Oil Sludge Disposal Areas), Site 7 (Ordnance Burn Area), Site 9 (Industrial Wastewater Disposal Area), Site 11 (Industrial Wastewater Disposal 100 Area), Site 49 (TCE Groundwater Plume in the 400 Area), and SWMU 87. http:www.epa.govsuperfundsitesrodsfulltextr2006030001473.pdf
Steckler, David, Steven G. Kawchak, and Michael Liskowitz. Vegetable Oil Emulsion Promotes Contaminant Degradation in Bedrock Groundwater. Technology News and Trends. December 2009. http:www.clu-in.orgdownloadnewsltrstnandt1209.pdf
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