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. A S S O C I A T E S I N C SAMPLING ACTIVITIES On June 11, 2003, ATC personnel collected groundwater samples from monitoring wells MW1 through MW10, and the on-site groundwater supply well DW 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) d>-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 MW 1, MW2, MW3 and MW6 contained the highest concentrations of TPHg and BTEX Groundwater samples collected from wells MW4, MW7, MW8, and MW10 also contained detectable concentrations of TPHg and BTEX constituents Detectable concentrations of TPHg ranged from 280,000 parts per billion (ppb) in MW2 to 120 ppb in well MW10 Detectable concentrations of benzene ranged from 22,000 ppb in MW2 to 3 8 ppb in well MW4 The groundwater samples collected from wells MW5 and MW9 contained no detectable concentrations of TPHg or BTEX Groundwater samples collected from wells MW1 through MW10 contained no detectable concentrations of oxygenate fuel additives although many of the reporting limits were elevated due to dilution factors The groundwater sample collected from on-site supply well DW labeled as influent water contained detectable concentrations of TPHg and BTEX, but contained no detectable concentrations of oxygenate fuel additives Analytical results of groundwater samples are summarized in Table 2 Laboratory data sheets and chain-of-custody documentation are contained in Attachment 2 GROUNDWATER FLOW DIRECTION Water level measurements were collected from wells MW1 through MW10 on June 11, 2003 Water levels in the shallow aquifer ranged from 64 96 to 66 68 feet below the tops of the well casing elevations, representing an average increase in the shallow water table elevation of • approximately 0 47 feet since March 2003 The water level data were used to develop the groundwater elevation contour map (F>gurelf Assuming that horizontal isotropic conditions vyy' e S\Enviromentai1163931REPORTs12gr-2003 doc 3