Laserfiche WebLink
yU_)OUO-.).)4 l,uw-jO <br /> PCE are denser than water, and this will also tend to cause downward <br /> movement of the contaminant plume. <br /> 4.3.5.4.2 To evaluate the extent of contamination, wells have been <br /> located in the Upper, Middle, and Lower Horizons. This procedure provides <br /> information on both the lateral extent of contamination at each of the <br /> three horizons, and the vertical extent of contamination. Because some <br /> contamination was found in the Lower Horizon, two wells (Wells LM 52 and LM <br /> 57) were screened in the first coarse unit beneath the Lower Horizon to <br /> complete the evaluation of the vertical extent of contamination. <br /> 4.3.5.4.3 Contours have been drawn on the contaminant concentrations <br /> in each of the horizons on the accompanying figures. In areas where there <br /> are insufficient data to adequately define the or-ientation of contaminant <br /> contours, an attempt has been made to draw the contamination contours <br /> approximately perpendicular to groundwater contours. <br /> 4.3.5.4.4 Available information indicates that Contaminant Areas 1, 2, <br /> 3, and 4 are responsible for-most of the onsite and offsite contamination <br /> at the Depot. As a result,-'the-extent of contamination associated with <br /> these areas is discussed in detail beginning in Section 4.3.5.4.5 below. <br /> In contrast, Contaminant Areas 5 and 6 show little or no contamination in <br /> concentrations which exceed the MCLS and hence are not judged to be sources <br /> of significant groundwater plumes. <br /> l <br /> 4.3.5.4.4.1''- Hydrochemical data from wells in the vicinity of <br /> Contaminant Area__5 indicate that the area is not a source of a <br /> significant plume (Figures 4.3-1 and 4.3-2) . Water from Well LM 37, <br /> which is located in Contaminant Area 5 and screened primarily in the <br /> Upper Horizon, showed nondetection for PCE and a concentration <br /> of 12 ug/l for TCE. However, chemical analyses of water from Wells LM <br /> a< <br /> 38, LM 86, and LM 90, located downgradient and screened in the Upper, <br /> Middle, and Lower Horizons, respectively, all showed nondetection for <br /> both TCE and PCE. This indicates that there is not a significant plume <br /> associated with Contaminant Area 5, and as a result, no further effort <br /> 4-174 <br />