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LEEDSHILL•HERKENHOFF. INC. <br /> EXECUTIVE SUMMARY <br /> ' Contamination of the upper water bearing zone by PCE and TCE has been con- <br /> firmed through samples obtained from monitoring well #4 installed within 50 <br /> ' feet of LVMD #1. None of the other monitoring wells (MW#1, #2 or #3) <br /> contained detectable chemical concentrations. The direction of groundwater <br /> flow in the upper water bearing zone is generally easterly to northeasterly. <br /> ' A monitoring well installed by Chevron, located 900 feet downgradient from <br /> LVMD #1, showed no detectable concentrations of PCE or TCE. No downgradient <br /> domestic wells exist within one mile of the site. Based on limited data, <br /> ' the direction of groundwater flow in the deeper semi-confined aquifer ap- <br /> pears to be toward the cone of depression created by LVMD #1 and #2. There <br /> is a static water level differential of approximately 12 feet between the <br /> ' upper and lower water bearing units. Based on this information and evalua- <br /> tion of the existing hydrogeologic conditions at this site, these water <br /> bearing zones appear to be hydraulically separate. From previous sampling <br /> and analysis of samples collected from LVMD #1 and #2 by others, the lower <br /> aquifer does not appear to be contaminated. <br /> ' The upper water bearing zone was contaminated by leakage of PCE/TCE waste <br /> water through joints in the existing sewer lines. This contamination is <br /> ' probably the result of long-term low-level discharges, rather than an iso- <br /> lated, single discharge event. LVMD #1 was contaminated by a failure in the <br /> casing and/or the surface sanitary seal , which allowed this contaminated <br /> water from the upper water bearing zone to enter the well . <br /> ' A contamination source is the dry cleaning establishments located at Lincoln <br /> Village Center. Soil samples collected beneath the foundations of these <br /> facilities and sewage samples collected from sewers serving these building <br /> ' showed detectable concentrations of PCE and/or TCE. <br /> It is unlikely that either of the sewers near LVMD #1 are continuing sources <br /> ' of groundwater contamination. First, all the joints within a one-hundred <br /> foot radius of LVMD #1 have been inspected and sealed. Also, soil samples <br /> ' collected beneath the sealed sewer lines were dry, indicating that water <br /> leakage had stopped. <br /> : t <br />