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chevron Products company 4 <br /> Chevron Service Station#9-6258 2409 East Main Street,CA July 28 1999 <br /> Attachment C Certified analytical reports and chain-of-custody <br /> documentation are presented as Attachment D. <br /> CONCLUSIONS <br /> The following conclusions are drawn from the findings summarized above <br /> • The site is underlain by layers of fine-grained sediments (sandy silts and silty clays), <br /> and coarse-grained sediments (silty sands, and sands) Groundwater was initially <br /> encountered between approximately 48 and 54 feet bgs at the site, and stabilized at <br /> approximately 48 feet bgs Groundwater flow direction was to the east at an <br /> approximate gradient of 0 0005 <br /> • Soil analytical data reported the presence of methanol at a maximum concentration of <br /> 250 mg/kg (MW-1 @ 25') Methanol is a common laboratory contaminant There is <br /> no known or suspected source of methanol at the site No other analytes were <br /> detected in the soil samples analyzed It is considered probable that the reported <br /> concentrations of methanol were the result of laboratory contamination <br /> • Groundwater analytical results reported relatively low concentrations (1 37 to 4 20 <br /> µg/l) of tetrachloroethene(PCE) in each of the wells No other analytes were <br /> detected in groundwater PCE use is commonly associated with dry cleaners and <br /> industrial processes, though small concentrations have been associated with solvent <br /> disposal in waste-oil tanks PCE was not detected in soil at the site (including <br /> samples previously collected by Pacific from directly beneath the waste-oil tank) An <br /> offsite source for the PCE detected in groundwater is considered probable <br /> RECOMMENDATIONS <br /> Based on the above conclusions, SECOR recommends continued monitoring of the wells <br /> for one year, at which time, the need for continued me*utoring and, if hydrocarbon <br /> concentrations remain consistent, site closure, should be evaluated Groundwater <br /> samples collected during these monitoring events should be analyzed for TPH-g, BTEX, <br /> and fuel oxygenates as well as PCE <br /> 76007-018-01/bormp <br />