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ATC Associates Inc Project No 99975 7501 <br /> concentrations of benzene detected (in monitoring well BEI-MW3) during the two monitoring <br /> events following remediation system shutdown,average less than 120 Pg/1 Risk based corrective <br /> action assessments for commercial/industrial sites with similar contaminant and subsurface <br /> characteristics have established target goals for benzene several times greater than the remaining <br /> concentration of benzene at the subject site <br /> Although formerly impacted soil has not been sampled, the hydrocarbon concentrations in the <br /> ' extracted soil vapor, declining from moderately high to non-detectable levels,provide evidence <br /> that remediation of the soil has been achieved More conclusive evidence that hydrocarbons have <br /> been removed from the soil is the lack of rebound in the detected hydrocarbons in groundwater <br /> nearly one year after active remediation at the site had ceased <br /> The site is free of the the gasoline oxygenates,including MTBE The absence of these oxygenates <br /> 1 has been well established by analyses The remaining concentrations of TPHg and benzene are <br /> readily biodegradable and will most certainly continue to biodegrade toward non-detectable <br /> levels <br /> Based u onthe evidence presented and summarized in this report,including monitoring data over <br /> a period of approximately one year following cessation of active remediation, and upon the <br /> conclusions cited above, ATC contends that further investigative or remedial activity at the site <br /> is no longer warranted The presence of the existing monitoring and extraction wells at the site <br /> are now considered to represent more of a hazard than do the remaining concentrations of <br /> petroleum hydrocarbons <br /> It is ATC's recommendation, therefore, that the site be considered for immediate closure and <br /> because the site is no longer involved with dispensing petroleum hydrocarbons, that all existing <br /> monitoring and extraction wells be appropriately destroyed <br /> 6.0 CERTIFICATION <br /> ' This report has been reviewed and approved by the client or responsible party To the best of our <br /> ' knowledge, all statements and information provided in this report are true and correct <br /> ' Reviewed by <br /> , <br /> a,. �J cam) Y-�� <br />- ' Ranald W Michelson James A Lehrman, RG, CIIG - <br /> Principal Geolo s 4t r �O�tr f Program Director Subsurface/Remediation <br /> M ct� I& <br /> r No. 3875 <br /> &f's C�/0 7, <br /> u���f3"4;�t~�F�'�� 6 <br />