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I C L E A2R'�-W"'xA T E R G R o LI •P, I N C ' Prior to sampling, each monitoring well was gauged to the nearest hundredth of a foot The wells were then purged of at least three well casing volumes while monitoring the purge water temperature, conductivity, and pH. The wells were ' purged until the parameters stabilized or until the well went dry. Monitoring well gauging and purge data are included in Appendix A. IEach groundwater sample was collected with a dedicated polyethylene bailer and was transferred to sample containers appropriate for the required analyses Sample ' containers were labeled with well numbers and placed in a cooler. A chain-of- custody was prepared and accompanied the samples to the laboratory Groundwater sample analysis was performed by American Environmental Network (AEN), DHS- certified laboratory located in Pleasant Hill, California All groundwater samples were analyzed for TPHg by EPA Method 8015 (CA LUFT modified), and for BTEX by EPA Method 8020 (CA LUFT modified) I 4.0 RESULTS ' 4.1 Water Level Monitoring Data Groundwater elevations are presented on Table 1 The depth to groundwater in the monitoring wells ranged from 24 02 to 24 62 feet on August 30, 1995 The depth to groundwater was measured relative to mean sea level, from the survey mark on top I of each well casing Groundwater elevation contours are presented on Figure 3 The local groundwater flow direction was calculated to be towards the northeast at an approximate gradient of 0 6% (0 006 feet/foot), which is consistent with results Iobtained during previous monitoring events. 4.2 Groundwater Analytical Results IA summa of analytical results is resented on Table summary y p e 1 and on Figure 4. None of I the analytes were detected in concentrations exceeding method detection limits in groundwater sample MW-1. TPHg was detected in all groundwater samples except MW-1; the highest detected concentration was 800 parts per billion (ppb) in MW-3 I Benzene was detected in groundwater samples MW-2, MW-3 and MW-4, the highest detected concentration was 230 ppb in sample MW-3 The laboratory report and chain-of-custody form are attached as Appendix B Prior to this sampling event, hydrocarbons had not been detected in groundwater samples from MW-5, the downgradient well. Results of sampling during the fourth quarter will be used to assess the potential migration of dissolved hydrocarbons in groundwater. ID-103 3Q95 2 October 20, 1995 I