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1 <br />' • have been a release from the former 2,500-gallon UST located at the <br /> • There appears to ha <br />' site However, the magnitude of the release appears to have had a limited impact to soil <br /> and groundwater beneath the site, <br />' • It appears there has been an impact to soil and groundwater beneath the site from a <br /> release of PCE However, only one shallow (16-foot) soil sample from the boring in the <br />' former UST location (MW-2) exhibited an elevated concentration of PCE to soil The <br /> two other PCE detections in deeper soil from borings MW-3 and MW-4 may be <br />' representative of soil that has been in contact with contaminated groundwater due to <br /> seasonal fluctuations to groundwater levels, <br />' • No distinct source of chlorinated solvents was evident based on the limited detections in <br /> the soil samples analyzed, <br />' • With the exception of arsenic, metals concentrations in soil did not exceed U S EPA <br /> Region IX PRGs Concentrations of arsenic detected are consistent with the range of <br />' background concentrations of arsenic in California soils, <br />' • Concentrations of PCE, TCE, and BEP in groundwater exceed their respective Primary <br /> MCLS TPH as diesel was detected in two groundwater samples, but only at very low <br />' concentrations There is currently no Primary MCL for TPH as diesel, <br /> • Additional site characterization work would be required in order to characterize the <br />' horizontal and lateral extent of groundwater contamination at the site, <br /> • Based on groundwater flow direction information generated during this investigation, <br />' groundwater is flowing to the northeast across the site at an average gradient of <br /> approximately 0 0031 This may indicate that contaminants detected in groundwater in <br />' MW-1 may originate from an upgradient, offsite source, <br />' Based on the conclusions presented above, URS makes the following recommendations <br />' • Continue quarterly groundwater monitoring at the site to confirm results of the first <br /> quarterly sampling event and evaluate the potential for migration of groundwater <br /> contamination onto the Unifyrst site from an offsite upgradient source, <br /> • Update the well search previously conducted by EEC to assess potential impacts to <br />' downgradient wells from off site migration of identified groundwater contamination <br />' 14 V\Goodwin ProctorlFinal Report doc <br />