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SP-1 The detection of TPH-G in MW-11, SP-4 and SP-6 samples may be an anomaly because it had not been measured in samples from these wells before, or because their relative distance from the source of the release ' TPH-G level increases and decreases were evident during this most recent monitoring compared to historic results Increases were noted at MW-7 and PZ-1 Decreases were seen at MW-12 and SP-2 ' SPI PSC observed a lower than expected BTEX to TPH-G concentration ratio in samples from MW-1, MW-7, SP-1, SP-2 and PZ-2 Total BTEX in the current MW-1 sample was measured at 2,176 ug/l compared to its TPH-G concentration of 14,000 ug/1 Total BTEX in the PZ-2 sample was measured at 470 ug/l compared to its TPH-G ' concentration of 13,000 ug/1 Much of the total BTEX in these two samples was comprised of xylenes This data suggests that the air sparging remediation system was having an affect on the more Ivolatile, lighter range petroleum fractions Groundwater samples from the CPT borings were used to assess the ' vertical extent of petroleum impact at the site BTEX and TPH-G Ievels were measured in the 90-feet depth sample from CPT-A, but v they were non-detect in its 100-feet depth sample Petroleum concentrations were detected in the 60-feet depth groundwater samples from CPT-C and CPT-F, however, they were non-detect at samples collected below that depth Based on this information, PSC conservatively estimates that the vertical extent of total petroleum impact at the site is approximately 90 feet Relatively higher petroleum levels appear to occur at depths shallower than 70 feet ' 3.4.2 June 2004 Oxygenate Conditions In Groundwater Current DIPE concentrations display general decreases since the operation of the air sparging remediation system, particularly since the - installation of sparge well SP-A DIPE was only measured in the sample from MW-12 and the 60-feet depth sample from CPT-F at concentrations of 14 ug/l and 37 ug/l, respectively (At 5 o m(,0 7 u+ 9 4 )L D 1 PE) Pz-1 u.} Ly L D)VE The compound 1,2-DC as detected in five groundwater samples, VY& r�' �f collected from MW-5,� W-S, MW-10, MW-12 an P-5 These measurable concentrations ranged from 0 5 ug/l to ug/l PSC was unable to discern a pattern of where this compound was detected relative to the former USTs Wells MW-10 and SP-5 are situated ' relatively distant from the former USTs, and samples from wells adjacent to the USTs did not contain detectable 1,2-DCA , ' 14 June 2004 Site Investigation Report The Earthgrains Company Facility 2651 South Airport Way-Stockton,California Prepared for SARA LEE SAKFNG GROUP Prepared by Philip Services Corp H U16240013251213828GAStocktonUtme 2004 Investigation R"n doc August 9,2004