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ATC Associates Inc
<br /> VYJN
<br /> Irc
<br /> 1117 Lone Palm Avenue, Suite B
<br /> Modesto, California 95351
<br /> 209-579-2221
<br /> ' A S S O C I A T E S 1 N C Fax 209-579-2225
<br /> ' GROUNDWATER FLOW DIRECTION
<br /> DTW measured in MW I through MW6, MW8 and MW9 on August 18, 2006, ranged from 67 78
<br /> ' to 74 65 feet below the top-of-casing elevations, representing a net average decrease in the
<br /> groundwater table elevation of 0 92 feet since the May 24, 2006 monitoring event (Table 1) The
<br /> DTW data were used to develop the groundwater elevation contour map (Figure 3) Based on
<br /> ' the August 18, 2006, monitoring data collected, the average hydraulic gradient is calculated to be
<br /> 0 04 ft/ft, approximately 2112 ft/mile, towards the southeast
<br /> ' GROUNDWATER ANALYTICAL RESULTS—August 18, 2006
<br /> TPHg was detected in groundwater samples collected from MW I through MW6 at
<br /> ' concentrations of 280 micrograms per liter (ug/L), 27,000 ug/L, 190 ug/L, 710 ug/L, 890 ug/L
<br /> and 3,400 ug/L, respectively Figure 4 depicts the relationship of dissolved TPHg across the
<br /> monitoring well network The greatest TPHg concentration was observed in MM2, which is
<br /> ' located in proximity to the former USTs and product-dispensing island
<br /> Benzene was detected in groundwater samples collected from MW2 through MW6 at
<br /> concentrations of 2,700 ug/L, 12 0 ug/L, 14 0 ug/L, 9 3 ug/L, and 110 ug/L, respectively Figure
<br /> 5 depicts the relationship of dissolved benzene across the monitoring well network The greatest
<br /> ' benzene concentration was observed in MW2, which is located in proximity to the former USTs
<br /> and product-dispensing island
<br /> Toluene was detected in groundwater samples collected from MW i, MM2, MW4, and MW6 at
<br /> ' concentrations of 0 9 ug/L, 620 ug/L, 1 4 ug/L, and 9 8 ug/L, respectively
<br /> Ethylbenzene was detected in groundwater samples collected from MWI, MW2, MW4, and
<br /> ' MW6 at concentrations of 0 6 ug/L, 530 ug/L, 2 3 ug/L, and 1 5 ug/L, respectively
<br />' Total Xylenes were detected in groundwater samples collected from AMI, MW2, MW4, and
<br /> MW6 at concentrations of 3 0 ug/L, 1,300 ug/L, 8 0 ug/L, and 2 4 ug/L, respectively
<br />' MTBE was detected in groundwater samples collected from MW1, MW3, and MW6 at
<br /> concentrations of 0 8 ug/L, 2 0 ug/L, and 160 ug/L, respectively Figure 6 depicts the relationship
<br /> of dissolved MTBE across the monitoring well network
<br /> TBA was detected in the groundwater sample collected from MW6 at 39 u
<br /> 1,2-DCA was detected in groundwater samples collected from MW I, through MW6 at 5 6 ug/L,
<br /> 26 0 ug/L, 9 9 ug/L, 5 6 ug/L, 3 5 ug/L and 460 ug/L, respectively
<br /> S Asa 2951 0001\0&M1s1-W-200&dm 4
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