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<br /> (Figure 3) Shallow groundwater beneath the site generally flowed towards the northeast The
<br /> average hydraulic gradient on July 5, 2005, was calculated to be approximately 00006 ft/ft or
<br /> approximately 3 2 ft/mile A summary of groundwater monitoring data is presented in Table 1
<br /> SAMPLING ACTIVITIES
<br /> On July 5, 2005, ATC personnel collected groundwater samples from monitoring wells MWl
<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 was measured in each well and the pH, electrical
<br /> conductivity, and temperature were measured in groundwater purged from the monitoring wells and
<br /> recorded A minimum volume of three well casings was purged from each well prior to sampling
<br /> The wells were allowed to recover and samples were collected from each well using a disposable
<br /> bailer
<br /> The groundwater matrix samples collected from each well were submitted to State-certified Argon
<br /> Laboratories (Environmental Laboratory Accreditation Program Certificate No 2359) for chemical
<br /> analyses of TPHg utilizing EPA Method 8015M, BTEX utilizing EPA Method 802113, and gasoline
<br /> oxygenates/additives including MTBE, ETBE, DIPE, TBA, TAME, 1,2-DCA, and EDB utilizing
<br /> EPA Method 8260B Groundwater well purge and 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 /> TPHg was detected in the groundwater samples collected from MW I, MW2, MW3, MWS, and
<br /> MW6 at concentrations of 380 micrograms per liter (µg/L), 1,900 gg/L, 250 gg/L, 1,300 gg/L, and
<br /> 520 pg/L, respectively Benzene was detected in the groundwater sample collected from MW2 and
<br /> MW6 at concentrations of 9 7 µg/L and 1 0 }ig/L, respectively Toluene was detected in the
<br /> groundwater samples collected from MW1, MW2, MW3, MWS, MW6, and MW7 at concentrations
<br /> of 0 8 µg/L, 6 5 gg/L, 1 1 gg/L, 6 0 gg/L, gg/L, 2 0 gg/L, and 1 3 µg/L, respectively Ethylbenzene
<br /> was detected in the groundwater samples collected from MW1, MW2, MW3, MW5, MW6, and
<br /> MW7 at concentrations of 1 7 µg/L, 110 gg/L, 1 7 gg/L, 33 µg/L, 13 µg/L, and 0 7 µg/L,
<br /> respectively Xylenes were detected in the groundwater samples collected from MW1, MW2, MW3,
<br /> MW5, MW6, and MW7 at concentrations of 5 0 gg/L, 85 gg/L, 3 8 gg/L, 130 µg/L, 25 pg/L, and 2 7
<br /> gg/L, respectively
<br /> MTBE was detected in the groundwater samples collected from MW1, MW2, MW3, MW4, and
<br /> MW7 at concentrations of 21 µg/L, 32 gg/L, 51 gg/L, 31 µg/L, and 30 gg/L, respectively TBA was
<br /> detected in the groundwater samples collected from MW 1, MW2, MW3, and MW7 at concentrations
<br /> of 43 µg/L, 41 gg/L, 40 gg/L, and 49 gg/L, respectively 1,2-DCA was detected in the groundwater
<br /> samples collected from MW1 through MW7 at concentrations ranging from 2 9 pg/L to 43 µg/L
<br /> The Maximum Contaminant Level (MCL) for benzene, 1 gg/L, was exceeded in the groundwater
<br /> sample collected from MWI The MCL for MTBE, 13 µg/L, was exceeded in the groundwater
<br /> samples collected from MW1, MW2, MW3, MW4, and MW7 The MCL for 1,2-DCA, 0 5 µg/L.,
<br /> was exceeded in the groundwater samples collected from all of the monitoring wells The California
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