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� v 0 I A S S O C I A T E 5 I N C DCA, and EDB were not detected in any of the samples A summary of petroleum hydrocarbon constituents detected in the groundwater samples collected during the groundwater extraction events is presented in Table 1 A graph depicting benzene concentrations detected in these samples is Included as Figure 3 Field notes associated with the extraction events are included in Attachment 1 ' QUARTERLY GROUNDWATER MONITORING AND SAMPLING On December 8, 2003, ATC personnel collected groundwater samples from monitoring wells MW1, ' MW2, and MW3 The locations of the monitoring 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 volume of three well casings was purged from each well prior to sampling The wells were allowed to recover and samples were collected from each well using disposable bailers 1 The groundwater samples collected from each well were submitted to State-certified Argon Laboratories for chemical analyses of TPHg utilizing EPA Method 8015B, and BTEX and MTBE utilizing EPA Method 8021B Groundwater well purge and sample logs are contained in Attachment 2 Analytical Results The laboratory analytical results indicate TPHg, toluene, ethyl benzene, and xylenes were detected in the groundwater sample collected from monitoring well MW1 at concentrations of 1,400 pg/L, 1 2 ' pg/L, 16 gg/L, and 10 gg/L, respectively Benzene and MTBE were not detected in the sample collected from M W 1 ' TPHg, toluene, and ethyl benzene were detected in the groundwater sample collected from monitoring well MW2 at concentrations of 310 gg/L, 0 8 pg/L, and 0 7 gg/L, respectively Benzene, xylenes and MTBE were not detected in this sample 1 TPHg, toluene, ethyl benzene, and xylenes were detected in the groundwater sample collected from monitoring well MW3 at concentrations of 1,200 pg/L, 0 8 gg/L, 7 7 gg/L, and 9 6 Pg/L, respectively Benzene and MTBE were not detected in the sample collected from MW3 The Maximum Contaminant Level (MCL) for benzene, 1 pg/L, was not exceeded in any of the groundwater samples Groundwater Flow Direction Water level measurements were collected from monitoring wells MW1, MW2, and MW3 on December 8, 2003 Water level elevations ranged from 36 83 to 36 89, representing an average increase in water table elevation of approximately 1 13 feet since September 2003 The water level data were used to develop the groundwater elevation contour map (Figure 4) Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed toward the northwest The average hydraulic gradient on December 8, 2003 was calculated to be 0 0007 or approximately 3 8 ft/mile Summaries of groundwater monitoring data and analytical results are presented in Table 2 and Table 3, respectively r' s lenvironmentall149811Reportsl4QR-03 doe 3 MI - — - - - -