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1444 MARIPOSA ROAD <br /> ' WKA No 293 8 06 <br /> • September 6, 2000 <br /> ' Page 17 <br /> a The source petroleum hydrocarbons (underground storage tanks, dispenser <br /> ' islands, and associated piping)has been removed <br /> a A majority of the contaminated soil has been removed from the former UST <br /> ' excavation, aerated and placed back in the excavation,thus posing no significant <br /> threat to groundwater quality <br /> ' a The contaminant release occurred prior to the 1992 tank removal and only trace <br /> concentrations of contaminants are present in groundwater directly beneath the <br /> ' -former excavation and at the property boundaries, it appears that a certain degree <br /> of natural attenuation is working to degrade the problem and limit the lateral <br /> migration of any remaining petroleum hydrocarbons <br /> a The laboratory data obtained during our most recent field work appears to indicate <br /> that a very limited amount of contaminated soil remains beneath the site in the <br /> ' relative vicinity of the former excavation <br /> a The subsurface soil and groundwater beneath the site has been adequately <br /> characterized We estimate that approximately 3 gallons of petroleum <br /> hydrocarbons (0 07 gallons of benzene)remain in subsurface soils and <br /> ' approximately 48 gallons of petroleum hydrocarbons (0 35 gallons of MTBE and <br /> 1 gallon of benzene)remain in groundwater in the vicinity of the former USTs <br /> ' a Petroleum hydrocarbons have decreased sigruficantly in groundwater samples <br /> collected from monrtonng wells MW1, MW2 and MW3 located in the vicinity of <br /> the underground storage tanks <br /> ' a Groundwater flow direction has consistently been to the east and southeast since <br /> at least 1997 <br /> ' a No detectable concentrations of petroleum hydrocarbons have been reported in <br /> downgradient wells (MW4 and MW8) located between known contamination and <br /> the on-site industrial supply wells with the exception of 0 49 µg/l detected in <br /> MW4 on January 1, 1995 <br /> a The inactive onsite domestic well has not been impacted with petroleum <br /> hydrocarbons or oxygenates <br /> ' a MTBE has not been detected in groundwater beneath the site <br /> o00 <br /> WALLACE KUHL <br /> Recyded paper Fr ASSOCIATES INC <br />