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Y <br /> MR Iffl, <br /> 0GEOL�GiC A5SFS5, fEIT!' <br /> 7910 Laver Sacra=nto Road,Stockton,California <br /> Delta Project Mo.4488-147 <br /> Page 11 <br /> In Delta's opinion, based on data collected from tite site, the concentrations of TPH detected at tank <br /> sampling locations T-S through T-8,and pump island sample T-3 are confined to a small volume of soil, <br /> and that the clayey soils beneath the site inhibit vertical migration of the petroleum constituents present. <br /> Laboratory analysis of soil samples collected within 10 feet of the%ater table from all six soil borings <br /> advanced at the site shows concentrations of petroleum constituents below detection Limit;. It is Deltas <br /> opinion t <br /> t p that the small quantity of sail containing petroleum constituents does not pose a threat to ground <br /> water. Tlie concentrations of benzene detected in ground water collected in monitoring wells MW-1 <br /> through MW_3'are below DHS action limits of 1.0 ppb,and based on the graund water flow direction, <br /> 4 4 determined at this site, the highest benzene concentration was detected in the monitoring well located <br /> fF upgradient from the former tank excavation,MW.1. This suggests that the dissolved benzene constituents <br /> I in ground water underlying the site may Originate from a location off site,upgradient from monitoring well <br /> The analytical results from soil samples collected during the Phase I Field Investigation indicate that <br /> ! Petraletun constituents detected in soils during the tank removal do not pose a threat to ground mater. <br /> if In addition,benzene concentrations detected inground water samples are below DHS <br /> action levels. For <br /> these reasons,Delta f.mommends that no further action be taken'at this site,and we request tha.r!site' <br /> closure letmr be prepared and submitted to our client,Shell oil Company.. <br /> ti <br /> F <br />