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[ � KLEINFELDER
<br />'• In June 2004, PSC performed the additional subsurface investigation Continuous soil
<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 (DIPS), 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 soli-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 Site Investigation 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,
<br /> SP-1, 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 /> C23-484517-BOO/SAC5R610 Page 4 of 12 September 14, 2005
<br /> Copyright 2005 Klemfelder, Inc
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