AECOM conducted an in situ chemical oxidation (ISCO) pilot study forthe Pennsylvania Department of Environmental Protection (PADEP) at a former platingfacility located in Upper Milford Township, Pennsylvania (Site). Located south of Allentown,Pennsylvania, the Site operated as an electroplating and polishing facility from theearly 1960s to the early 1980s. Site characterization data indicated that the primary contaminantof concern (COC), trichloroethene (TCE), has been observed at a concentration of40,000 μg/L within the weathered/fractured bedrock of the source area. Tetrachloroethylene(PCE) and degradation byproducts of TCE and PCE are present at significantly lowerconcentrations within the source area and wider dissolved plume. Elevated concentrationsof chlorinated solvents also exist in the deep portion of the fractured bedrock aquifer. Evidencesuggests that dense nonaqueous-phase liquids (DNAPLs) contained in the aquiferunderlying the source area are serving as a residual source of chlorinated solvents to thegroundwater. Former operations at the Site present the possibility of metal mobilization;however, the depth, distribution, and concentrations of the COCs lend themselves to anISCO application within the source area.The conceptual treatment approach for the pilot study utilizes the density contrast betweenthe sodium permanganate (NaMnO4) solution and groundwater, as well as, the totalvolume of liquid to be injected. A conceptual site model was developed, where the denserNaMnO4 solution achieves a radius of influence (ROI), sinks to the top of the weatheredbedrock, and ultimately travel laterally along the surface of the competent bedrock untilencountering the naturally occurring fractures within the competent bedrock. A thoroughunderstanding of overlying unconsolidated material (soils), weathered bedrock interface,and locations of primary fractures in the competent bedrock was essential in developing theconceptual site model and subsequent remedial approach.The first objective of the pilot study was to verify the connectivity of bedrock fractureswithin the source area. The second objective was to perform source control by oxidizingCOCs in situ by injecting NaMnO4 at and near the source area via existing monitoringwells and strategically located injection/monitoring wells. The oxidant was injected at theweathered bedrock interface with the potential for the oxidant to migrate downward to fractureslocated in the competent bedrock. The third objective was to utilize the pilot test datato optimize a full-scale design and gather real time treatment information regarding contaminantreductions.The pilot test has been completed over three (3) injection periods utilizing gravityflow/low pressure to deliver the NaMnO4 due to the proximity of sensitive receptors (I.e.,surface water and water supply wells). The effectiveness of each injection event for oxidiz-
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