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4,5 Analysis of System Effectiveness
<br /> Figures 14 through 20 are cross plots of benzene and MTBE over time Figures 21, 22 and 23
<br /> show the areal distribution of the same analytes (i e , benzene, MTBE and TPHg) respectively,
<br /> based on isoconcentration maps over time
<br /> 4.51 Benzene
<br /> Prior to remediation system start-up on June 17, 2004 at the Jamar property, benzene
<br /> concentrations appeared to decline in MW2, MW3, MW4, MW5 and MWS Declining trends in
<br /> benzene concentration were not evident, however, in MWI and EW1 prior to start-up Benzene
<br /> concentrations show an overall decrease in MWI and EW1 from system start-up
<br /> During the second quarter monitoring period concentrations of benzene from MWI and EW1
<br /> placed respectively at approximately 7 5 and 9 0 feet from the closest Spargepoint®
<br /> (respectively, IW2 and IW 1) remained either below the Maximum Contamination Limit (MCL)
<br /> for drinking water or below method detection limits The overall declining trend (with only slight
<br /> fluctuations) of benzene in MWI from the 37,000 ug/L on June 3, 2004 in the quarterly
<br /> monitoring events following that event (i e , September 13, 2004, December 13, 2004, March 16-
<br /> 17, 2005, and June 21-22,2005) was significant During the second quarter 2005 event, benzene
<br /> was reported at 2 4 ug/L for MWI, which is a removal efficiency exceeding 99 9% after
<br /> approximately 12 months of operation
<br /> The overall decline of benzene in EW1 from the 35,000 ug/L on June 3, 2004 in each of the
<br /> quarterly groundwater monitoring events (following that event) also was significant Benzene
<br /> was not detected at method detection limits of 0 5 ug/L in EWl for the April 22, 2005 and May
<br /> 25, 2005 system monitoring events and during the June 21-22, 2005 groundwater-monitoring
<br /> event During the June 21-22, 2005 event, a removal efficiency exceeding 99 9% was achieved
<br /> after approximately 12 months of operation or less
<br /> During the June 21-22, 2005 monitoring event, concentrations of benzene from MW2 declined
<br /> from the previous quarterly groundwater-monitoring event Concentrations of benzene in MW3
<br /> have been reduced by over 95% since system startup in June 2004, from 790 ug/1 on June 3, 2004
<br /> to 37 ug/l on June 21, 2005
<br /> Benzene in MW4 was reduced to a non-detection level (<0 5 ug/L) on December 13, 2004 and
<br /> remained at that level through the first and second quarter 2005 monitoring events (conducted on
<br /> March 16-17, 2005 and on June 21-22, 2005) MW4 is approximately 16 feet from
<br /> Spargepoint® IW4 The decline of benzene in MW4 may have accelerated after system start-up
<br /> from the 1,500 ug/L on June 3, 2004 to later monitoring events (i e , September 13, 2004,
<br /> December 13, 2004, March 16-17, 2005, and June 21-22, 2005)
<br /> If the reduction in concentration in MW4 was attributed solely to system activities, this would
<br /> . equate to a removal efficiency exceeding 99 9% during the operating period (Note In addition,
<br /> dissolved oxygen (DO) concentrations have increased notably in MW4 after system start-up The
<br /> increase in DO after system start-up would indicate influence by the C-SpargeTM process )
<br /> S 1268231QM reports12005 2ndQR doc 9
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