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. QUARTERLY GROUNDWATER MONITORING AND SAMPLING REVIEW QUARTERLY GTS MONITORING AND SAMPLING REVIEW 4614 W TURNER RD. , LODI PAGE 2 Following the initial excavation, 15 soil borings were drilled, between May 15 and June 2 , 1989 Laboratory results of soil analyses determined the presence of petroleum hydrocarbons in concentrations exceeding 100 mg/kg in the area surrounding the tank excavation. After completion , 10 of the borings were converted to groundwater monitoring wells (Figure 2 ) Initial sampling of the wells indicated the presence of benzene in concentrations above the DHS Maximum Contaminant Levels (MCL ' s) for drinking water in three of the wells . In the fall of 1992 , a groundwater treatment system was installed in MW 1 . A report on the installation of this system has been submitted to San Joaquin Public Health Services and to Central Valley Regional Water Quality Control Board Groundwater and- Groundwater -Treatment System (GTS) Monitoring and Sampling _ Results from earlier quarterly samplings have been submitted in previous reports The quarterly sampling covered in this report was conducted by Caltest Analytical Laboratories The results of the findings are summarized in the following sections Groundwater levels are presented in Table 1 Analytical results are presented in Table 2 Copies of the laboratory reports are presented in Attachment I . THIRD QUARTER 1994 - Sampled on August 25 and September 6 , 1994 : Groundwater levels were obtained from monitoring wells #1 , #3 , and #5 Samples were obtained from monitoring wells #1 and #3 at the site Due to an error in sampling , monitoring well #1 had to be resampled on Sept 6 . Monitoring Well #1 has been converted into an extraction well However , the GTS was temporarily not operational , so the pump was removed from the well and a sample was taken with a bailer MW-9 was damaged in 1990 and cannot be sampled. The remaining wells were not scheduled to be sampled during this round of sampling The influent and effluent to the GTS were not sampled, as the system was temporarily not running Groundwater levels at the three points average 17 04 feet below the surface This represents an average drop of 0 . 47 feet from the second quarter of 1994 Lab analysis shows trace amounts of three contaminants in MW-1 8 . 1 ppb Benzene, 6 8 ppb Ethylbenzene , and 7 . 8 ppb Xylene , no detectable toluene , and no detectable Total Petroleum . Hydrocarbons as Gasoline (TPHg) In MW-3 , lab analysis shows 120 . 0 ppb TPHg, and no detectable amounts of any other contaminants .