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1.2.2 AnalVtical Results for Groundwater <br /> Three monitoring wells (MW-1, MW-2 and MW-3) were installed <br /> around the area of the tank removal to monitor the first encoun- <br /> tered shallow groundwater at the site. Groundwater samples were <br /> collected from each of the three wells. No floating product was <br /> i observed in any of the three monitoring wells. Samples from well <br /> MW-1, upgradient from the tank removal area, did not exhibit <br /> ctable concentrations of any analytical parameter. Well <br /> 1# dete <br /> : Betelocated closest to the tank removal area, contained the <br /> most elevated concentrations of chemical residues. The compounds <br /> detected include heavy and light TPH fractions, organolead and <br /> BTX&F, <br /> organolead and BTX&E were also detected in MW-3, <br /> downgradient of the tank removal area. The concentrations were <br /> significantly lower in MW-3 than in MW-2 except for organolead. <br /> The results are summarized in Table 1-2. <br /> 1.2.3 Conclusions of initial Investigation <br /> Based on the above investigation, hydrocarbon compounds were <br /> detected in soils and groundwater at the site in excess of <br /> typical guidar_ce cleanup levels and Maximum Contaminant Levels <br /> (MCLS) for soils and drinking water, respectively. <br /> These results <br /> �-} dictated the need for remediation of both soil and groundwater. <br /> 14 A review by the San Joaquin Local Health District staff concluded <br /> that the initial soil investigation had adequately defined the <br /> L, �... <br /> lateral and vertical extent of hydrocarbon residues in the soil <br /> and that remediationwas required. Several remedial options were <br /> f considered and soil removal and disposal was selected as the most <br /> cast effective solution for the site. The selection of this <br /> remedial alternative was due to the short time available for <br /> remediation prior to building on the site. <br /> w . was removed from the site by excavation <br /> Hydrocarbon bearing sail <br /> of a pit roughly 58 feet wide by 44 feet long down to approxi- <br /> mately 30 feet. This excavation resulted in removal of approxi- <br /> mately 2000 cubic yards of soil which removed the majority of <br /> hydrocarbon bearing soils from the site. Figure 1-3 depicts the <br /> size and location. of this excavation. The resulting pit was <br /> backfilled and compacted with clean fill. material. <br /> While the source material has been effectively removed, the <br /> levels of hydrocarbon residues found in the groundwater 'the <br /> and MW-3 suggested the presence of a residue plume beneath <br /> s�_e, In order to define the lateral and vertical extent of this <br /> suspected plume, the Health District determined that additional <br /> *- groundwater investigation is needed at the site. <br /> r ; <br /> - 1 - 5 <br />