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' QUARTERLY GRDUNDWATER MONnDRING REPORT <br /> 7910 Lower Sacramento Road Stockton Calitornia <br /> ' In January 1992, Emcon was retained by Shell to collect measurements of depths to and <br /> groundwater samples from the three wells on site The data, including the laboratory <br /> ' analytical reports, was then provided to Aegis for inclusion in this report (Appendices A <br /> and B) <br /> ' 4 0 GROUNDWATER MONITORING <br /> 41 Groundwater <br /> On February 20, 1992, Emcon personnel collected measurements of depths to <br /> ' groundwater in each of the three wells according to the Emcon sampling procedures (SP) <br /> included in Appendix A Water level measurements collected since the wells were <br /> installed are summarized in Table 1 A groundwater elevation hydrograph is included as <br /> ' Figure 3 <br /> Since November 1991, groundwater levels have risen in all wells an average of 1 35 feet <br /> On the basis of the February 20, 1992, measurements, groundwater is estimated to flow <br /> to the northwest (Figure 4) at an average gradient of approximately 0 001 ft/ft The <br /> ' previous estimated direction of groundwater flow was to the northwest <br /> 4 2 Water Sampling and Analysis <br /> On February 20, 1992, Emcon personnel collected groundwater samples from wells <br /> MW-1, MW-2, and MW-3 The samples were delivered under chain-of-custody to Sequoia <br /> ' Analytical of Redwood City, California, a state-certified analytical laboratory, for chemical <br /> analysis Sample collection was conducted according to the Emcon SP included in <br /> Appendix A The samples were analyzed for concentrations of TPH, as gasoline, by EPA <br /> ' Method 8015, and BTEX by EPA Method 8020 Concentrations of TPH, as gasoline, and <br /> benzene were reported below the detection lima in MW-1, MW-2, and MW-3 <br /> ' The analytical results summarized in Table 2 are also shown on Figure 5 Sample <br /> handling and chain-of-custody procedures are addressed in the Emcon SP included in <br /> Appendix A The laboratory reports and chain-of-custody form are included in <br /> ' Appendix B <br /> 1 <br /> 1 <br /> 91 231A OMR 2 <br />