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GROUNDWATER MONITORING AND SAMPLING REPORT <br /> BP Oil Company Service Station No. 11193 <br /> 3202 West Hammer Lane <br /> Stockton, California <br /> Project No. 10-136 <br /> May 5, 1993 <br /> INTRODUCTION <br /> This report presents the results and findings of the April 4 and 26, 1993 groundwater <br /> monitoring and April 4, 1993 sampling conducted by Alisto Engineering Group at BP Oil <br /> Company Service Station No. 11193, 3202 West Hammer Lane, Stockton, California. A site <br /> vicinity map is shown in Figure 1. <br /> FIELD PROCEDURES <br /> Field activities were performed in accordance with the procedures and guidelines of the <br /> San Joaquin County Public Health Services Department and the California Regional Water <br /> Quality Control Board, Central Valley Region. <br /> Before purging and sampling, the groundwater level in each well was measured from a <br /> permanent mark on the top of the casing to the nearest 0.01 foot using an electronic sounder. <br /> The depth to groundwater and top of casing elevation data were used to calculate the <br /> groundwater elevation in each well in reference to mean sea level. The survey data and <br /> groundwater elevation measurements collected to date are presented in Table 1. <br /> Before sample collection, each well was purged of 3 casing volumes, while recording field <br /> readings of pH, temperature, and electrical conductivity. Groundwater samples were <br /> collected for laboratory analysis by lowering a bottom-fill, disposable bailer to just below the <br /> water level in the well. The samples were transferred from the bailer into laboratory- <br /> supplied containers. The water sampling field survey forms are presented in Appendix A. <br /> SAMPLING AND ANALYTICAL RESULTS <br /> The results of monitoring and laboratory analysis of the groundwater samples for this and <br /> previous quarters are summarized in Table 1. The potentiometric groundwater elevations as <br /> interpreted from the results of the April 4 and 26, 1993 monitoring events are shown in <br /> Figures 2 and 3. The results of groundwater analysis are shown in Figure 4. The laboratory <br /> report and chain of custody record are presented in Appendix B. <br /> 10-136-1.QNU050493 <br />