Bedrock is a gneiss comprised of light gray-white plagioclase feldspar with lenses of quartz and minor biotite mica. Core samples displayed thin to thick veins of calcite, thin veins of pitted pyrite and slickensides with slight offsets. High angle fractures were observed in cores with major fracture spacing between 4 and 6 ft.
The depth to ground water and bedrock are approximately 15 ft and 45 ft, respectively.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
This was source zone treatment - 100ft by 40ft.
Major Contaminants and Maximum Concentrations:
- Trichloroethene (200,000 µg/L)
- Pumping Tests
- Fracture Trace Analysis
- Coring
- Chemical Oxidation (In Situ)
Comments:
Based upon the results of conceptual site model development and remedial alternative identification, chemical oxidation was selected as a remedial alternative for pilot testing. Sodium permanganate was chosen as an oxident because it is relatively safer to use than alternatives and does not require additional catalists or pH adjustment. Both injection and recirculaion were implemented in order to better control the distribution of the permanganate in the fractured bedrock aquifer. Overburden and bedrock hydraulic gradients were monitored via down-hole pressure transducers to determine any potential changes to TCE migration and/or gradients caused by the injection and recirculation of the solution.
Post I&R ground water sampling data indicated concentrations of TCE were reduced from between 100,000 to 150,000 ug/L to below 1 ug/L in the injection well. Concentrations in monitoring wells were reduced from approximately 150,000 ug/L to less than 1 ug/L initially and to between 30,000 and 50,000 ug/L once rebound occurred. Post I&R monitoring did not indicate uncontrolled migration of the permanganate solution.
Reduce the concentrations from the source zone
Full-scale source area implementation is currently in progress and is comprised of two additional open bedrock boreholes, injection and extraction manifolds with flow monitoring devices and pressure gages, and permanganate dosing and injection equipment. Ongoing full-scale implementation and monitoring is projected to occur over the next two years.
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