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Soil Excavanpn Romft Repan <br /> 509 Hamner Lane StXO=n GalAomm <br /> Figures 2 and 3 show the approximate final extent of the excavation, soil sampling <br /> . locations and depths, and TPH as gasoline analytical results The complete analytical <br /> Iresults are included in Table 1 <br /> Based on the previous boring results, the final excavation depth was approximately 22 <br /> to 25 feet below grade Figure 3 and Table 1 show that all samples analyzed contained <br /> less than 100 parts-per-million (ppm) TPH as gasoline, except sample S-3 at 22 feet <br /> This area was excavated to 25 feet and sample 5-11, collected approximately two feet <br /> I from S-3, verified removal of the impacted material Overall, the total of twelve soil <br /> samples collected and analyzed confirm successful removal of affected soil <br /> Analytical results from SB-9 indicated soil from 26 to 31 feet contained TPH as gasoline <br /> concentrations ranging from 180 to 240 ppm Because of equipment limitations, this soil <br /> could not be removed However, assuming this soil extends in a 5-foot radius around the <br /> boring location an estimated 8 6 pounds (or less than 1 5 gallons) of residual TPH <br /> remains in the soil The 5-foot radius assumption is based on the approximate lateral <br /> extent of TPH in the soil around SB-9 at depths of 21 to 22 feet (Figure 3) The <br /> hydrocarbon mass calculation is shown in Attachment 4 No benzene, the most mobile <br /> of the gasoline constituents was detected in any of the recent soil boring and excavation <br /> samples However, benzene laboratory detection limits were occasionally elevated <br /> Ibecause of interference from TPH concentrations Analytical results from SB-9 indicated <br /> soil from 26 to 31 feet contains benzene concentrations below detection limits ranging <br /> from 0 005 to 0 05 ppm Assuming a worst case concentration of 0 05 ppm and soil <br />!, extending in a 5-foot radius around the boring location, an estimated 0 0022 pounds of <br /> residual benzene remains in the soil This calculation is also shown in Attachment 4 <br /> Based on the aata and calculations outlined above remaining hydrocarbons in the soil <br /> do not appear to threaten the relatively deep groundwater Therefore, Aegis recommends <br /> I this site for certified closure by San Joaquin County and the California Regional Water <br /> Quality Boara Central Valley Region <br /> I <br /> I <br /> i <br /> I7�G05A RER <br /> I <br />