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<br /> A s s O C I A T E s I N C
<br /> towards the northeast The average hydraulic gradient on April 9, 2004 was calculated to be 0 0009
<br /> ft/ft or approximately 4 6 ft/mile A summary of groundwater monitoring data �s presented in Table
<br /> 1
<br /> SAMPLING ACTIVITIES
<br /> On April 9, 2004, ATC personnel collected groundwater samples from monitoring wells MWI
<br /> through MW7 The locations of the monitoring wells are shown on Figure 2 Prior to collection of
<br /> groundwater samples, the depth to water, pH, electrical conductivity, and temperature were measured
<br /> in groundwater purged from the monitoring wells and recorded A minimum volume of three well
<br /> casings was purged from each well prior to sampling The wells were allowed to recover and
<br /> samples were collected from each well using a disposable bailer
<br /> The groundwater matrix samples collected from each well were submitted to State-certified Argon
<br /> Laboratories (ELAP Cert No 2359) for chemical analyses of TPHg utilizing EPA Method 8015B,
<br /> BTEX utilizing EPA Method 8021B, and gasoline oxygenates/additives including MTBE, ETBE,
<br /> DIPE, TBA, TAME, 1,2-DCA, and EDB utilizing EPA Method 8260B Groundwater well purge and
<br /> sample logs are contained in Attachment 1
<br /> ANALYTICAL RESULTS
<br /> • The laboratory analytical results )Indicate petroleum hydrocarbons were detected in the groundwater
<br /> samples collected from all of the monitoring wells
<br /> Benzene was detected in the groundwater samples collected from MWI and MW2 at concentrations
<br /> of 13 micrograms per liter gg/L and 2 8 pg/L, respectively Toluene was detected in the groundwater
<br /> samples collected from MW2, MW3, MWS, and MW6 at concentrations of 2 1 gg/L, 1 1 gg/L, 6 0
<br /> gg/L, and 1 8 gg/L, respectively Ethylbenzene was detected in the groundwater samples collected
<br /> from MWI, MW2, MW3, MWS, MW6, and MW7 at concentrations of 1 8 pg/L, 14 pg/L, 1 9 gg/L,
<br /> 31 gg/L, 42 gg/L, and 0 7 pg/L, respectively Xylenes were detected in the groundwater samples
<br /> collected from MWI, MW2, MW3, MWS, MW6, and MW7 at concentrations of 3 6 gg/L, 18 gg/L,
<br /> 3 8 gg/L, 230 µµIL, 18 gg/L, and 12 gg/L, respectively MTBE was detected in the groundwater
<br /> samples collected from MWI, MW2, MW3, MW4, and MW7 at concentrations of 23 pg/L, 21 gg/L,
<br /> 46 gg/L, 24 gg/L, and 30 pg/L, respectively TBA was detected in the groundwater samples collected
<br /> from MW 1, MW2, MW3, and MW7 at concentrations of 33 gg/L, 36 µµIL, 32 pg/L, and 41 gg/L,
<br /> respectively 1,2-DCA was detected in the groundwater samples collected from MWI through MW7
<br /> at concentrations ranging from 4 4 gg/L to 59 gg/L TPHg was detected in the groundwater samples
<br /> collected from MW1, MW2, MW3, MWS, MW6, and MW7 at concentrations of 360 gg/L, 750
<br /> pg/L, 240 gg/L, 1,700 gg/L, 450 gg/L, and 130 gg/L, respectively
<br /> The Maximum Contaminant Level (MCL) for benzene, 1 pg/L, was exceeded in the groundwater
<br /> samples collected from MWI and MW2 The MCL for MTBE, 13 gg/L, was exceeded in the
<br /> groundwater samples collected from NMI, MW2, MW3, MW4, and MW7 The MCL for 1,2-DCA,
<br /> 0 5 gg/L, was exceeded in the groundwater samples collected from all of the monitoring wells The
<br /> �• California Drinking Water Action Level for TBA, 12 gg/L, was exceeded in the groundwater
<br /> samples collected from MW1, MW2, MW3, and MW7 A summary of the laboratory analytical data
<br /> is presented in Table 2 A copy of the laboratory analytical report is Included in Attachment 2 An
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