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KLEINFELDER
<br /> In June 2004 PSCerformed the additional subsurface investigation Continuous soil
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<br /> lithology, from ground surface to a depth of 100 feet was evaluated at CPT-A boring
<br /> location using an electronic cone penetrometer system Seven CPT borings (CPT-A, -
<br /> B, -C, -D, -E, -F, and -G) were in the vicinity of the former gasoline USTs Soil samples
<br /> were collected from the borings and were submitted for the analysis The analytical
<br /> parameter list includes benzene, toluene, ethylbenzene, xylenes, (BTEX), total
<br /> petroleum hydrocarbons as gasoline (TPH-G), the oxygenate analytes of tertiary butyl
<br /> alcohol (TBA), methyl tertiary butyl ether (MTBE), di-isopropyl ether (DIPE), ethyl
<br /> tertiary butyl ether (ETBE), and tertiary amyl methyl ether (TAME), 1,2-dichloroethane
<br /> (1,2-DCA), and ethylene dibromide (EDB), using test method SW-846 / 8021/8260B
<br /> Groundwater samples were collected at three of the boring locations and were
<br /> submitted for the same analytical parameters The CPT soil investigation indicated that
<br /> the residual petroleum-hydrocarbon impact that remained after the 1987 excavation was
<br /> sufficiently addressed by the soil-vapor-extraction system that operated at the site and
<br /> that the mass-of-impact in the vadose zone was negligible The CPT groundwater
<br /> investigation was used to assess the vertical extent of petroleum impact at the site
<br /> Based on the data obtained, PSC conservatively estimates that the vertical extent is
<br /> approximately 90 feet bgs Although, the relatively higher petroleum concentrations
<br /> appear to occur at depths shallower than 70 feet bgs PSC reported the results from
<br /> the investigation in the June 2004 Sfte lnvestrgat_on Report Additionally, groundwater
<br /> samples were collected from all of the on-site monitoring wells and two nearby private
<br /> wells This groundwater-monitoring event indicated that the lateral extent of impacted
<br /> groundwater is largely contained within the Earthgrain's property boundaries In
<br /> addition, historical and current decreases of petroleum impact to groundwater have
<br /> been observed, which are likely due to natural degradation and the use of air sparging
<br /> as a remedial method Based on the findings of this investigation, PSC recommended
<br /> ' one more groundwater-monitoring event be performed, in which groundwater samples
<br /> would be collected from wells MW-1 , MW-5, MW-7, MW-8, MW-10, MW-11, MW-12,
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<br /> SPA, SP-2, SP-4, SP-6, PZ-1 , and PZ-2 Although, the analytical parameter of EDB
<br /> would not be performed, since it was not detected during the investigation Upon
<br /> completing the next quarterly event, PSC would prepare a report and propose either site
<br />' closure or additional remedial work The SJCEHD approved the recommendations in a
<br /> letter dated September 24, 2004 Although, they requested that the remaining wells
<br /> MW-2, MW-3, MW-4, MW-6, MW-9, and MW-13 be placed on the annual groundwater
<br /> monitoring program to track the plume However, SJCEHD requested that the quarterly
<br /> depth-to-groundwater and total-depth measurements be performed in all wells They
<br /> C23-484517-BOO/SAC5R608 Page 4 of 11 September 14, 2005
<br /> Copyright 2005 Kleinfelder, Inc
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