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JUJUVU-JJY ..V1 -`iv <br /> PCE concentration of 0.6 ug/l . In general , groundwater flow direction in <br /> the vicinity of the Depot is towards the north or northeast, and hence, <br /> contamination should not move from Well LM 24 toward LM 1 unless <br /> groundwater flow direction in the vicinity of LM 1 differs from the <br /> direction elsewhere in the area. Because of the presence of the Stormdrain <br /> Holding Pond and the Sanitary Settling Ponds, it is possible that a <br /> groundwater high is present. This could cause contamination to pass around <br /> the ponds to the east and west. Contamination contours shown on Figure <br /> 4.3-2 are drawn on the assumption that the ponds influence groundwater flow <br /> and that the PCE observed in LM 1 is derived from the vicinity of LM 24. <br /> 4.3.5.4.11 The distribution of TCE in the Middle Horizon is shown on <br /> Figure 4.3-3. TCE was detected in three wells (LM 40, LM 55, and LM 67) , <br /> located in or downgradient of Contaminant Area 2. It was not detected in <br /> any other wells screened in the Middle Horizon. PCE was detected in only <br /> two wells (LM 55 and LM 67) screened in the Middle Horizon (Figure 4.3- <br /> 4) . Analyses of water samples from all other wells (onsite and offsite) <br /> screened in the Middle Horizon showed no detection. <br /> 4.3.5.4.12 TCE and PCE were identified in three wells screened in the <br /> Lower Horizon (LM 56, LM 70, and.Raspo 3 Ag) . Raspo 3 Ag (an agricultural <br /> well used by Mr. Raspo to irrigate his walnut orchard adjacent to the <br /> Depot) has multiple screens, with the uppermost screen being located in the <br /> Lower Horizon. The concentrations of TCE and PCE measured in Raspo 3 Ag <br /> are interpreted-to be the concentrations present in the Lower Horizon., The <br /> lateral extent of both TCE and PCE in the Lower Horizon is well-defined by <br /> either nondetection or concentrations below the MCL in wells which surround <br /> LM 56 (Figures 4.3-5 and 4.3-6) . <br /> 4.3.5.4.13 Two wells (LM 52 and LM 57) are screened in relatively <br /> coarse sediment located 20 to 40 feet below the Lower Horizon (see Cross <br /> Section A-A, Figure 3.4-2) . Neither TCE nor PCE was detected from water <br /> samples taken from Wells LM 52 and LM 57, indicating that contamination <br /> does not extend to the depth of the screens of these wells. <br /> 4-184 <br />