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<br /> ATC Associates Inc
<br /> 1117 Lone Palm Avenue, Suite B
<br /> Modesto,Califorma 95351
<br /> 209-579-2221
<br />. Fax 209-579-2225
<br /> AS SOCIATES INC
<br /> GROUNDWATER FLOW DIRECTION
<br /> Groundwater level measurements collected from monitoring wells MWl through MW7 on October
<br /> 12, 2005, ranged from 44 34 to 46 91 feet bgs Groundwater elevations ranged from -29 56 to -
<br /> 29 70, representing an average increase in the groundwater table elevation of approximately 6 3 8 feet
<br /> since July 2005 The water level data were used to develop the groundwater elevation contour map
<br /> (Figure 3) Shallow groundwater beneath the site generally flowed towards the northeast The
<br /> average hydraulic gradient on October 12, 2005, was calculated to be approximately 0 0013 ft/ft or
<br /> approximately 6 9 ft/mile A summary of groundwater monitoring data is presented in Table 1
<br /> SAMPLING ACTIVITIES
<br /> On October 12, 2005, ATC personnel collected groundwater samples from monitoring wells MW 1
<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 8021B, and gasoline
<br /> oxygenates/additives including MTBE, ETBE, DIPS, 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 MW1, MW2, MW3, MW5, MW6,
<br /> and MW7 at concentrations of 280 micrograms per liter (pg/L), 850 pg/L, 180 gg/L, 630 pg/L, 220
<br /> pg/L, and 160 pg/L, respectively Benzene was detected in the groundwater samples collected from
<br /> MW2 and MW6 at concentrations of 4 8 pg/L and 0 9 µg/L, respectively Toluene was detected in
<br /> the groundwater samples collected from MW1, MW2, MW3, MW5, MW6, and MW7 at
<br /> concentrations of 0 7 pg/L, 17 pg/L, 1 8 pg/L, 4 8 pg/L, 3 0 pg/L, and 2 1 gg/L, respectively
<br /> Ethylbenzene was detected in the groundwater samples collected from MW1, MW2, MW3, N11W5,
<br /> and MW7 at concentrations of 19 pg/L, 35 pg/L, 18 gg/L, 49 gg/L, and 1 1 pg/L, respectively
<br /> Xylenes were detected in the groundwater samples collected from MW1, MW2, MW3, MW5, MW6,
<br /> and MW7 at concentrations of 4 9 pg/L, 51 pg/L, 2 1 pg/L, 92 pg/L, 9 1 pg/L, and 4 4 gg/L,
<br /> respectively
<br />• MTBE was detected in the groundwater samples collected from MW1, MW2, MW3, MW4, and
<br /> MW7 at concentrations of 14 µg/L, 58 pg/L, 53 pg/L, 23 pg/L, and 37 gg/L, respectively TBA was
<br /> detected in the groundwater samples collected from MW 1, MW2, MW3, MW6, and MW7 at
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