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7 <br /> The groundwater extraction and treatment system was turned off for the majority of the <br /> permanganate pilot study. As a basis for comparison in terms of operational efficiency, <br /> 1999 data for the groundwater extraction and treatment system indicate this system would <br /> have removed an estimated 120 pounds of TCE during these six months. <br /> 4.3 Evaluation of Effects of KMn04 on Inorganic Compounds <br /> All inorganic parameters were monitored and plotted as a function of time indicate a return <br /> to background levels approximately 2 to 8 weeks after permanganate injection. This <br /> included monitoring and sampling for major cations, total dissolved solids (TDS), metals in <br /> soils (As, Cr, Mo, Se, U, and V were the trace metals analyzed in soil samples) and <br /> groundwater (Cr, Se, U, and V were the trace metals analyzed in groundwater samples). <br /> 4.4 Evaluation of Effects of Permanganate on Aquifer Permeability <br /> The hydraulic conductivity values calculated from pre- and post-injection slug test data <br /> were within 54 to 160 feet per day (ft/day), plus or minus two orders of magnitude. Since <br /> both tests resulted in similar hydraulic conductivity values, there is no indication of <br /> changes to aquifer permeability from the injection of permanganate, or precipitation of <br /> manganese dioxide (Mn02). <br /> 4.5 Summary of Observations and Results <br /> The permanganate pilot study indicated the following: <br /> • Rebound of TCE concentrations was observed at most of the wells, and is <br /> probably a result of advection from areas upgradient of the pilot test and/or <br /> desorption of TCE from soils which did not come into contact with the potassium <br /> permanganate solution. <br /> • Evidence of permanganate presence in groundwater appeared limited to no <br /> greater than 20 feet from the injection points. <br /> • The wells with the highest concentrations of TCE show the highest decreases <br /> within the pilot study area during the first two weeks following permanganate <br /> injection <br /> • Background TDS concentrations from seven wells within the pilot study area <br /> ranged from 650 to 852 mg/L in July 1999. The TDS concentrations six months <br /> after permanganate injection of wells within the pilot study area ranged between <br /> 708 to 1,150 mg/L. The elevated TDS concentrations are associated with the <br /> KMn04 injections and were observed to persist a minimum of six months after the <br /> pilot study until groundwater extraction was re-started. <br /> • Multilevel injection on transects with hydraulic mixing appears is required for <br /> delivering permanganate to the subsurface in complex geologic conditions, as exist <br /> beneath the site. <br /> • Hydraulic conductivity (K) calculated from pre- and post-injection slug test data <br />