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1 A review of soil data collected to date appears to indicate that the maximum diesel fuel <br /> concentration and the areal extent of diesel fuel impact appears to have decreased over time <br /> Residual petroleum hydrocarbon concentrations are present at the site (less than 40 gallons <br /> diesel fuel), however, the concentrations which are potentially leachable are very low A <br /> review of groundwater analytical data collected from downgradient monitoring wells MW-1 <br /> and MW-2 appears to indicate no diesel fuel migration from the soil to groundwater The <br /> potential for migration of the residual diesel fuel is limited since the building and/or adjacent <br /> pavement which overlies the abandoned tanks and the former UST locations impedes the <br /> infiltration of surface water/precipitation and a confining clay/silt layer existings in between <br /> the impacted soils and groundwater <br /> Results of computer groundwater modeling suggest that the petroleum contaminants (currently <br /> present in the vadose zone) appear to pose no significant risk to groundwater quality <br /> Groundwater risk analysis predicts that the contaminants will not cause impact to the <br /> groundwater in concentrations above prescribed regulatory standards for drinking water <br /> Therefore, any potential impact to groundwater quality should pose no human health risk <br /> 11.0 Recommendations <br /> r Since it appears that extent of residual diesel impacted soils is highly limited and these soils <br /> pp P g Y <br /> i <br /> are isolated by man-made and geological factors, it appears that no significant threat to <br /> groundwater exists Analytical groundwater results indicate that no further investigation or <br /> remediation is warranted at this site at this time IT proposes that this case be reviewed for <br /> UST Closure requirements and be referred to the Regional Water Quality Control Board for <br /> their consideration <br /> 12.0 References <br /> y A list of references employed during modeling and reporting is included in Appendix E of <br /> this report <br /> 1p <br /> 11� <br /> � 1 <br /> MZJ04-06-95/UST/95-0089 17 <br />