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Mr. Maurice Benson <br /> December 15, 2009 <br /> Page 2 <br /> General Comments <br /> 1.) Data from the hydraulic fracturing fieldwork indicated that fractures followed <br /> natural preferential pathways in the subsurface, particularly propagating to the <br /> southwest direction. The report acknowledged that the fracture shapes and <br /> planes were not repeatable or predictable and led to non-uniform vertical and <br /> horizontal distributions of the oxidant. The non-uniform distributions of potassium <br /> permanganate (KMn04) would decrease the effectiveness of remediating <br /> contaminant mass in the saturated zone and would lead to pockets of untreated <br /> soil that would potentially act as continuing source of volatile organic compound <br /> (VOC) contamination to groundwater. <br /> 2.) The report identified that the tilt meter fracture mapping was not accurate in <br /> predicting the KMn04 fracture size. The mapping outputs measured the fracture <br /> created by the gel, not the extent that the viscous KMn04 slurry was emplaced, <br /> leading to over-prediction of oxidant propagation. <br /> Conclusions <br /> Emplacement of the KMn04 slurry in the subsurface saturated zone reduced volatile <br /> organic compounds in groundwater to below aquifer cleanup levels in localized areas. <br /> Hydraulic fracture propagations followed preferential pathways leading to non- <br /> repeatable or predictable, non-uniform vertical and horizontal distribution of oxidant <br /> slurry. Proprietary tilt meter fracture mapping over-predicted propagation of oxidant <br /> slurry by measuring the less viscous fracture gel. Unexpected surfacing of the oxidant <br /> during the fieldwork event more than doubled the time planned in the field. <br /> The report fails to directly address how the remedial action objectives of the fieldwork <br /> were met with respect to effectiveness, considering the uncertainties with efficient, <br /> targeted emplacement of the oxidant slurry to areas where VOC mass resides. The <br /> report should identify whether DESJC considers in-situ chemical oxidation using KMn04 <br /> combined with hydraulic fracturing as a viable technology for future remedial efforts. <br />