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KEI-P91-0202 .QR3 November 6, 1992 Page 3 The ground water sample analytical results are summarized in Table 3 . The concentrations of TPH as gasoline and benzene detected in the ground water samples collected this quarter are shown on the attached Figure 4 . Copies of the laboratory analytical results and Chain of Custody documentation are attached to this report. DISCUSSION AND RECOMMENDATIONS Based on the analytical results for the ground water samples collected and evaluated to date, and no evidence of free product or sheen in any of the wells, KEI recommends a modification to the current ground water monthly monitoring and quarterly sampling program. Since no evidence of free product or sheen has been detected in any of the wells to date, and since a consistent southerly flow S�^ direction has been established at the site, ,KEI recommends that the monitoring frequency be reduced from monthly to quarterly for all of the wells. The majority of the ground water samples collected from the wells during the past four quarters of sampling have shown non--detectable concentrations of TPH as gasoline and BTX&E. In addition, petroleum hydrocarbon contamination was only detected in one well (MW1) during the most recent sampling event on October 12 , 1992 . A Therefore, KEI recommends that the sampling frequency be reduced D�� . from quarterly to semi-annually for all of the wells. The results of the modified monitoring and sampling program will be documented and evaluated after each monitoring and sampling event, and recommendations for altering or terminating the program will be made as warranted. DISTRIBUTION A copy of this report should be sent to the San Joaquin County Local Health District, and to the Regional Water Quality Control Board, Central Valley Region. LIMITATIONS Environmental changes, either naturally-occurring or artificially- induced, may cause changes in ground water levels and flow paths, thereby changing the extent and concentration of any contaminants. Our studies assume that the field and laboratory data are reasonab- ly representative of the site as a whole, and assume that subsur- face conditions are reasonably conducive to interpolation and extrapolation.