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<br /> MTBE concentrations have marginally increased from the March 15-16, 2005 groundwater
<br /> monitoring event in MW2, MW5, MW6a, MW7b, and MW10a, and have substantially increased
<br /> in MW6b and MW6c
<br /> MTBE concentrations in MW10b, although decreasing from the December 13, 2004 groundwater
<br /> monitoring event, remain similar
<br /> MTBE concentrations in EW 1 appear to have decreased compared to levels from the second
<br /> quarter monitoring event of 2004
<br /> The change in areal extent of MTBE from the June 3, 2004 monitoring event through the June
<br /> 21-22, 2005 groundwater monitoring event appears negligible (Figure 22)
<br /> 4 5.3 TPHg
<br /> During this monitoring period, TPHg concentrations in MW4, MW6b, MW6c, MW7a, MW7b,
<br /> MW7c, MW8, MW9a, MW9b, MW9c, MWlOa, MW10b, and MWIOc were not detected at
<br /> method detection limits of 50 ug/L TPHg was detected in MW1, MW2, MW3, MW5, MW6a
<br /> and EW1
<br /> Although some fluctuations were apparent, the overall decline of TPHg in MW1 from 54,000
<br /> ug/L on June 3, 2004 in most of the quarterly monitoring events following (i a , September 13,
<br /> 2004 and December 13, 2004, March 16-17, 2005) was significant During the June 21-22 2005
<br /> groundwater monitoring event, TPHg was reported at 210 ug/L for a removal efficiency of 99 6%
<br /> r after approximately 12 months of operation
<br /> TPHg concentrations in MW2 and MW3 appeared to fluctuate during the second quarter TPHg
<br /> concentrations in MW2 ranged between 830 ug/L (on May 25, 2005) to 970 ug/L for each of the
<br /> system monitoring events during second quarter TPHg concentrations in MW3 ranged from
<br /> 1,600 ug/L to 2,400 ug/L during the second quarter
<br /> A decline of TPHg in MW4 has accelerated from 4,800 ug/L on June 3, 2004 to <50 ug/L on
<br /> December 13, 2004 and remained at not detected at method limits of 50 ug/L during the system
<br /> operating period since that time If this reduction was attributed solely to system activities this
<br /> would equate to a removal efficiency of 99 0%by December 13, 2004
<br /> MW6a shows a fairly consistent concentration of TPHg since December 13, 2004
<br /> The successive decline of TPHg in EW1 was also significant TPHg was present in
<br /> concentrations of 85,000 ug/L on June 3, 2004 It declined in the quarterly monitoring events
<br /> following except for the March 16-17, 2005 event, which is consistent with the second quarter
<br /> event During the June 21-22, 2005 event, TPHg was reported at 460 ug/L This equates to a
<br /> removal efficiency of 99 5% after approximately 12 months of operation
<br /> . TPHg maps were also plotted using data from the March 17, 2004, June 13, 2004, September 13,
<br /> 2004, December 13, 2004, March 16-17, 2005, and June 21-22, 2005 groundwater monitoring
<br /> S 1268231QM reports12005 2RdQR doc 11
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