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r A S S O C I A T E S I N C SAMPLING ACTIVITIES On September 9, 2003, ATC personnel collected groundwater samples from monitoring wells MW 1 through MW 10, and the on-site groundwater supply well DW (influent water) The locations of the wells are shown on Figure 2 Prior to collection of groundwater samples, the depth to water, pH, electrical conductivity, and temperature were measured in the monitoring wells and recorded A minimum of three well casing volumes were purged from each monitoring well prior to sampling The wells were allowed to recover and samples were collected from each well using disposable polyethylene bailers After the groundwater samples were collected, dissolved oxygen was measured in each well The groundwater samples collected from each well were submitted to State-certified Argon Laboratories Inc (ELAP Cert No 2359) in Ceres, California for chemical analysis of TPHg utilizing EPA method 8015 modified, benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA method 8020, and methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE) di-isopropyl ether (DIPE), tertiary amyl ether (TAME), tertiary butyl ether (TBA), 1,2- dichloroethane (1,2-DCA), and 1,2-dibromoethane (EDB) utilizing EPA method 8260 Groundwater well purge and sample logs are contained in Attachment 1 ANALYTICAL RESULTS Groundwater samples collected from wells MW1, MW2, MW3, MW6, and MWS and on-site groundwater supply well DW contained the highest concentrations of TPHg and BTEX Groundwater samples collected from wells MW4, MW7, and MW10 also contained detectable concentrations of TPHg and BTEX constituents Detectable concentrations of TPHg ranged from 300,000 parts per billion (ppb) in MW2 to 180 ppb in well MW10 Detectable concentrations of benzene ranged from 23,000 ppb in MW2 to 0 6 ppb in well MWIO The groundwater samples collected from wells MW5 and MW9 contained no detectable concentrations of TPHg or BTEX -Groundwater samples collected from wells MW 1 through MW10 and DW contained no detectable concentrations of oxygenate fuel additives although many of the reporting limits were elevated due to dilution factors Analytical results of groundwater samples are summarized in Table 2 Laboratory data sheets and chain-of-custody documentation are contained in Attachment 2 t- GROUNDWATER FLOW DIRECTION Water level measurements were collected from wells MW1 through MW10 on September 9, 2003 Water levels in the shallow aquifer ranged from 67 97 to 69 41 feet below the tops of the well casing elevations, representing an average decrease in the shallow water table elevation of • approximately 2 84 feet since June 2003 3The water level data were used to develop the groundwater elevation contour map (Figure;,) Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards the southeast The S 1EnviromentahI63931REPORTS13gr-2003 doe 3