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4.4 Analytical Results of Groundwater Samples Toluene and xylenes were detected in the sample from MW-9 at concentrations of 0 52 ppb and 2 9 ppb respectively No other petroleum hydrocarbons were detected in any of the samples The analytical results are summarized in Table 3 The laboratory report and chain- of-custody are included in Appendix C TABLE 3 ANALYTICAL RESULTS OF WATER SAMPLES Genova Bakery 749 North Sierra Nevada Street, Stockton, California (µPQ) Sample ID TPH as Gasoline Benzene Toluene benzene Xylene MW-8 ND ND ND ND ND MW-9 ND ND 052 ND 29 _ EW-1 ND ND ND ND ND AS/L parts per billion(ppb) .ND = hone Detected 5.0 CONCLUSIONS & RECOMMENDATIONS 5.1 Hydrocarbon Impacted Soil Borings CB-1 and CB-2 were installed to confirm the success of the vapor extraction system When EW-1 was drilled, no samples above 55 feet were analyzed However, PID readings were collected during drilling PID readings ranged from 1,719 ppm to 2,679 ppm in the interval from 15 feet to 45 feet in EW-1 indicating the presence of significant concentrations of petroleum hydrocarbons PID readings from CB-1 ranged from 0 ppm to 451 ppm in the same depth range Organic vapors were only detected from 35 feet to 45 feet in CB-2 This Irepresents a 94 1% reduction in organic vapors detected in this range The original estimate of the volume of gasoline in the soil was estimated assuming a cylindrical plume of 25 foot diameter and 40 foot depth and laboratory analyses The volume of gasoline was estimated to be 3,000 gallons The current volume of impacted soil is apprommately 10 feet thick, extending from a depth of 30 feet to 40 feet A pocket of impacted soil is also present near CB-1 at a depth of 20 feet This indicates that the current plume is approximately one quarter the volume of the original plume Concentrations of remaining petroleum hydrocarbons are also approximately one quarter that of the original concentrations G-bS-1...,s.— 1.[ 12 Gsaan 6.1x7 Qtt/7 9UI I I