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a • A S S O C I A T E S I N C 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 dedicated disposable 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 total petroleum hydrocarbons as gasoline (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, MW3,Aand 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 l Concentrations of TPHg ranged from 240,000 parts per billion (ppb) in well MW3 to 830 ppb in well MW10 Concentrations of benzene ranged from 14,000 ppb in well MW3 to 3 7 ppb in well MWIO The groundwater sample collected from wells MW5 and MW9 contained no detectable concentrations of TPHg or BTEX -/Groundwater samples collected from wells MW I and MW3 through MW10 contained no detectable concentrations oxygenate fuel additives although many of the reporting limits were elevated due to dilution The groundwater sample collected from on-site supply well DW 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 MWl through MW10 on June 25, 2002 r Water levels ranged from 62 95 to 64 66 feet below the tops of the well casing elevations, representing an average decrease in the water table elevation of approximately 1 09 feet since April 2002 The water level data were used to develop the groundwater elevation contour map (Figure,-A 'Asstitri'ing that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards the southeast The average hydraulic gradient on June 25, 2002 was calculated to be 0 005 ft/ft or approximately 26 ft/mile A summary of groundwater monitoring data is presented in Table I i w 1I63931quardyl2gr-2002 doe 3