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DEC-23--i993 16 01 FROM TO 1209 0133 P.02 <br /> G09 fer,rrer aria.tea. <br /> Figures 2 and 3 show the approximate final extent of the excavation, $oli sampling <br /> locations and depths, and TPH as 928otine snalyticel results. The complete analytical <br /> results are included in Tape I. <br /> Based on the previous boring results, the finale excavation depth was approximately 2.2 <br /> to 25 feet below grade Figure 3 and Table 1 show that al samples analyzed contained <br /> less than 100 parts-per-Mihcon (ppm) TPH as gasoline, except sample S-3 at 22 feel. <br /> This area was excavated to 25 fleet and sample S-11, collected approximately two feet <br /> from S-3, verified removal of the Impacted material. Overall, the total of twelve soil <br /> samples eoilettod and analyzed confirm sucaessful removal of affected sod <br /> Analytical results from Sf3-'8 indicated soil from 26 to 31 feet contained TPH as gasoline <br /> concentrations ranging tram 180 to 240 ppm_ Because of equipment limitations, this soil <br /> could not be removed. However,assuming this sod extends in a 5-lbot radius around the <br /> boring location, an estimated 8.6 pounds (or less than 1.6 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 Sly at depths of 21 to 22 feet (Figure 3) The <br /> hydrocarbon mass c alculabon 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 /> because of Interference from TPH c oncentreMons. Analytical results from S8-8 indicated <br /> soil from 26 to 31 feet contains benzene concentratiane below detewtian limits ranging <br /> from 0 005 to 0.06 ppm. Asmming a worst case concentration of 0 05 ppm, and loll <br /> extending in a 5-foot radius around the boring location, an estimated 0.0022 pounds of <br /> • residual benzene remains In Om sill. This caalculaflan is also shown in Attachment 4 <br /> Based on the data and cagculattons cutiined above, remonMg hydrocarbons in the sod <br /> do not aper to threaten the rellartively deep grourKNmter Therefom,Aegis recommends <br /> this sib Vor cerhfed cosure by San Joegiain County and the Calftmia regional Mter <br /> Qual <br />