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LEEDSHILL•HERKENHOFF, INC. <br /> During the video inspection, a layer of oil was found floating on the <br /> ' surface of the water. The source of this oil is probably over-lubrica- <br /> tion of the pump, with the excess oil accumulating on the water surface <br /> within the well . This is not an uncommon occurance. A sample of the <br /> ' floating oil was collected, and PCE was found at a concentration of <br /> 17,300 ppb. This high concentration is not unusual because of PCE's <br /> ' tendancy to adsorb to organic matter. <br /> During the pumping and recovery cycles of LVMD well #1, PCE levels in <br /> s ' LVMD well #6 remained below the DOHS action level of 4.0 ppb. Two <br /> months after well #1 was placed back in service, PCE levels rose in well <br /> #6 to 9.5 ppb. Subsequent testing in the following months showed PCE <br /> ' levels around the action level of 4.0 ppb. In December of 1986, the <br /> Department of Health Services requested that San Joaquin County Public <br /> Works cease using LVMD well #6 as a source of municipal water until <br /> further investigations could be completed. This well is still idle and <br /> has not been sampled since then. Table 2.2 presents the sampling his- <br /> tory of LVMD wells #1 and #6. <br /> 2.4.4 Chevron Monitoring Well <br /> In January 1987, due to leakage of an underground storage tank located <br /> at the Chevron USA gasoline station at LVC, a monitoring well was in- <br /> stalled near the intersection of Benjamin Holt Drive and Pacific Avenue. <br /> The well is 45 feet deep and monitors the upper water bearing zone. <br /> ' Representative split and duplicate samples collected and analyzed by the <br /> RWQCB for EPA 601 constituents showed no detectable concentrations of <br /> PCE or TCE. <br /> ' 2.5 Historical Source Investigation <br /> ' When PCE and TCE were first detected in LVMD well #1 in 1984, the San Joa- <br /> quin Local Health District instituted a preliminary investigation to deter- <br /> mine the possible source or sources. A list of all possible solvent users <br /> iin Lincoln Village Center was compiled and each of these businesses were <br /> inspected and the owners interviewed. Businesses which were identified as <br /> ' currently using PCE and TCE in their operations were three dry-cleaners; <br /> Village Cleaners, Finest Care Cleaners, and Morge Cleaners. Stores which <br /> were also investigated, but did not use PCE included Ace Litho, Village <br /> 2-10 <br /> 1 <br />