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r <br /> Former Beacon Station No 419 February 17, 1999 <br /> Stockton,California Additional Subsurface Investigation <br /> CONCLUSIONS <br /> Based on the data collected during this investigation, Horizon concludes the following <br /> r <br /> Soil: <br /> 0 Hydrocarbon-impacted soil appears to be limited to an area north of the UST <br /> cavity with significant impact limited to a depth of approximately 71 feet bsg <br />' • Oxygenated fuel additives are not present in soil in the impacted area, except for <br /> 0 41 ppm ethanol at 41 feet bsg in boring SB-6 <br /> I <br /> r Groundwater: <br /> • If the water sample collected with the HydroPuncho sampler from boring SB-6 at <br /> r88 to 91 feet bsg is representative of groundwater at the historically low <br /> groundwater level, then groundwater appears to be impacted by TPHg ana is FEX <br /> at depth <br /> • Oxygenated fuel additive compounds are not present in the groundwater at 88 to <br /> r91 feet bsg <br /> • On September 30, 1998, groundwater was present at a depth of approximately 48 <br /> rfeet bsg The groundwater gradient direction beneath the site was estimated to be <br /> toward the southwest at a magnitude of 0 003, utilizing data from the newly <br /> rinstalled wells MW-7, MW-8, and MW-9 <br /> rRECOMMENDATIONS <br /> rBased on the additional data collected during this investigation, Horizon recommends the <br /> following <br /> r <br /> r • Installation of a monitoring well with a depth-discrete screened interval to evaluate <br /> the HydroPunch'water sample collected in boring S13-6 <br /> r1419-12 rpt 10 HORIZON ENVIRONMENTAL INC. <br />