Groundwater is present in the underlying Brunswick Shale.
Targeted Environmental Media:
 Fractured Bedrock
Major Contaminants and Maximum Concentrations:
- Tetrachloroethene (4,000 µg/L)
- Borehole Geophysics
- Other (Down-hole geophysical testing)
- Vertical Chemical Profiling
Comments:
Bedrock investigation characterized the formation as having an average of 2 fractures per 10 vertical feet. Fractures were filled or partially filled with calcite or open but tightly spaced. The maximum achievable liquid injection rate without significant back pressure was 7.5 gallons/minute. Down-hole geophysical testing identified fractured zones with open boreholes for targeted injections.
- Fracturing
- Other (Biostimulation with bioaugmentation)
Comments:
Between 1,000 - 4,000 ug/L of Tetrachloroethene has been measured in the shallow bedrock below a former dry well. A pilot test for the selected remedial approach was performed which consisted of three injection wells and one monitoring well. Lateral substrate distribution was facilitated through the use of packers which isolated 4 to 5 fracture zones within each injection well. Horizontal substrate distribution was facilitated through the use of ARS Technologies patented Pneumatic Fracturing and Liquid Atomized Injection technology. Each fracture zone was treated with 60 to 75 gallons of dilute Slow Release Substrate (SRS" ) and was immediately followed with an equal volume of atomized chase water. The radius of influence was measured at 35-feet by both real-time data as well as post-injection measurements. Dissolved oxygen and oxidation/reduction potential reductions into anaerobic conditions were measured 90 feet in the down-gradient groundwater and bedrock strike direction. Three months after injection, bioaugmentation was performed.
Remediation goals were not identified in the abstract.
Sixty days after SRS" injection, groundwater data indicated anaerobic groundwater conditions that were favorable for reductive dehalogenation in a 30,000 square foot area around the injections wells and within the top 40 feet of the aquifer. Shallow bedrock monitoring wells located in the top 20 feet experienced: (1) a minimum of 90% Tetrachloroethene reduction, (2) minimal generation of Trichloroethene, 1,2-Dichloroethene, and Vinyl Chloride, and (3) 150-200% increases in hydrogen concentrations. Similar groundwater chemistry improvements were seen in the deep wells in the same area.
References:
Kirschner, Stephen W., Michael Lee, and Michael Liskowitz. Fracturing Emplaced Vegetable Oil Emulsion and Bioaugmentation in a Bedrock Aquifer. Presented at the Tenth International In Situ and On-Site Bioremediation Symposium. Baltimore, MD. May 5-8, 2009.
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