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' 31 March 2004 <br /> AGE-NC Project No 03-1077 <br />' Page 7 of 7 <br />' • Various BTEX compounds were detected in all groundwater samples except CPT-2-65-70, <br /> CPT-2-94-98 and CPT-2-106-110 MTBE was detected in only one sample (CPT-3-65-69) at <br /> a concentration of 3 7 µg/1 <br />' • The vertical extent of TPH-g-impacted groundwater is not defined(Figure 5),however, MTBE <br /> and the BTEX compounds benzene and toluene does not extend below the fine-grained interval <br /> at between 75 and 90 feet bsg (Figure 6), and the remaining BTEX compounds ethylbenzene <br />' and xylenes were present only in very low concentrations (below California Department of <br /> Health Service's Maximum Contaminant Level) <br /> 1 <br /> 5.0 RECOMMENDATIONS <br />' Based on the findings of this investigation AGE recommends <br /> I • Continue soil vapor extraction to remediate high petroleum hydrocarbon-impacted soil at the <br /> site <br /> • Additional assessment to define the vertical and lateral extent towards the north, south and east <br />' of petroleum hydrocarbon-impacted soil and groundwater,low concentrations of TPH-g(up to <br /> 400µg11)and below MCL levels of ethylbenzene and xylenes in boring CPT-2 suggest that the <br />' western extent of contamination is defined at the site CPT technology can be utilized for <br /> vertical assessment to approximately 100 feet bsg, if necessary, other drilling techniques such <br /> as sonic or hollow-stem auger can be utilized below 100 feet bsg <br />' • Preparation of a work plan to remediate high petroleum hydrocarbon-impacted soil and <br /> groundwater beneath the water table Possible remediation techniques may include ozone <br /> sparging and/or pump and treat <br /> I6.0 LIMITATIONS <br /> Our professional services were performed using that degree of care and skill ordinarily exercised by <br /> environmental consultants practicing in this or sirnllar localities The findings were based mainly upon <br /> analytical results provided by an independent laboratory Evaluations of the geologic/ hydrogeologic <br /> conditions at the site for the purpose of this investigation are made from a limited number of available <br /> data points(I a grab groundwater samples and soil samples)and subsurface conditions may vary away <br /> I from these data points No other warranty, expressed or implied, Is made as to the professional <br /> recommendations contained in this report <br /> I <br /> Advanced GeoEnviron mental,Inc <br />