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was made to define the extent of contamination associated with <br /> Contaminant Area 5. <br /> 4.3.5.4.4.2 The limited nature of contamination associated with <br /> Contaminant Area 6 is shown by three wells screened in the Upper <br /> Horizon and located in, or immediately downgradient of, Contaminant <br /> Area 6. These wells (LM 35, LM 36, and LM 82) showed either <br /> nondetection or contaminant concentrations which were either below or <br /> slightly above the MCL (Figures 4.3-1 and 4.3-2) . Only one sample (PCE <br /> from Well LM 35) exceeded the MCL, and that sample was only marginally <br /> above the MCL. Because of these low concentrations, no further <br /> investigation of this area was considered necessary. <br /> 4.3.5.4.5 Unlike Contaminant Areas 5 and 6, hydrochemistry indicates <br /> that Contaminant Areas 1 through 4 are significant sources of groundwater <br /> contamination, both onsite and offsite. Water from wells screened in or <br /> above the Upper Horizon in Contaminant Areas 1 and 2 have commonly shown <br /> elevated concentrations of TCE and PCE, as tabulated below. <br /> TCE PCE <br /> Well Contaminant Concentration Concentration <br /> Number Area (ug/1 ) (ug/1 ) <br /> LM 24 1 ND 15 <br /> LM 25 1 470 1.4 <br /> LM 61 1 15 20 <br /> LM 28 2 11 5.2 <br /> LM 30 2 38 340 <br /> LM 62 2 7.6 4.5 <br /> Similar results are present from groundwater samples collected from wells <br /> screened in or above the Upper Horizon in Contaminant Areas 3 and 4, as <br /> tabulated below. <br /> 4-177 <br />