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1 QUARTERLY GROUNDWATER MONITORING PROGRAM EAST BAY MUNICIPAL UTILITY DISTRICT ' SECOND QUARTER 1993 ' 1.0 INTRODUCTION The 1993 groundwater monitoring program at the East Bay Municipal District (EBMUD) Stockton Center (Figure 1) consists of monitoring the groundwater elevation in all seven wells ' on the site and sampling four of the seven wells for analysis of total petroleum hydrocarbons as gasoline (TPH-G) The purpose of the monitoring program is to acquire additional data on the distribution and concentrations of petroleum hydrocarbon compounds in groundwater beneath ' the site The scope of this monitoring program was agreed upon by EBMUD and the San Joaquin County Public Health Services Environmental Health Division (EHD) in a meeting between EBMUD and EHD on January 19, 1993 ' This report summarizes the sampling methods utilized and presents the field and analytical results for the second quarter 1993 groundwater monitoring event ' 2.0 GROUNDWATER MONITORING SUMMARY The groundwater monitoring and sampling work was conducted on May 28, 1993 Groundwater ' elevation measurements were collected in all seven wells prior to collecting groundwater samples from wells MW-1, MW-2, MW-5 and MW-7 One quality control equipment decontamination sample, labelled MW-9, was collected from the sample bailer after collecting primary sample MW-1 in order to evaluate the effectiveness of the decontamination procedure Monitor well locations are shown on Figure 2 and a detailed description of field activities is presented in Appendix A 2.1 Physical Parameters Summary ' Groundwater elevation data was used to determine the groundwater flow direction and gradient beneath the site shown on Figure 3 Groundwater elevation contours indicate that the groundwater flow is toward a groundwater trough trending west to northwest Groundwater physical parameters of temperature, pH and electrical conductivity were recorded during the ' purge of each well sampled and are presented in Table 1. 2.2 Chemical Analysis Summary Groundwater samples were collected for analysis of TPH-G from wells MW-1, MW-2, MW-5 and MW-7 The analytical results are summarized in Table 2 and the complete analytical report is presented in Appendix B All wells sampled contained no detectable hydrocarbons except for MW-1, which contained 310 µg/L of TPH-G The equipment decontamination sample, labelled MW-9, contained no detectable TPH-G which indicates that the bailer decontamination procedure was effective 1 ' 9MREPORTSt01MUMND WP 1 MOM