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Mr Jeff Wong <br /> February 13, 2006 <br /> Page 2 <br />' Concentrations of benzene in MW-2 were below the laboratory reporting limits for the second time in less <br /> than a one year period The benzene concentrations in MW-2 have remained under 2 0 micrograms per <br /> liter(NgIL)for a minimum of five consecutive quarters The benzene concentrations in MW-2 continue to <br />' have a downward trend <br /> MW-2 had reported concentrations of TPHd above the laboratory reporting limits (180 pg/L) The TPHd <br /> concentrations in MW-2 continue to have a downward trend and the fourth quarter 2005 data appears to <br />' be anomalous <br /> Cumulative groundwater sampling results are summarized in Table 1 A map depicting dissolved <br />' concentrations of TPHd, TPHg, benzene, and MTBE in groundwater for fourth quarter 2005 is included as <br /> Figure 4 A copy of the certified laboratory analytical report with chain-of-custody documentation is included <br /> in Attachment C <br />' A graph of TPHd, TPHg, benzene, and groundwater elevation versus time for MW-2 appears as <br /> Attachment D <br /> Conclusions/Recommendations <br /> Based on the demonstrated natural attenuation through time in concentrations of the contaminants of <br /> concern, groundwater at this site does not appear to pose a threat to human health or to the environment <br /> ENSR recommends suspension of monitoring activities and initiation of procedures leading to regulatory <br /> closure of this site <br /> Future Work <br /> Upon acceptance of the above recommendations regarding site closure, the groundwater monitoring wells <br /> will be properly abandoned or destroyed in accordance with San Joaquin County Public Health Services <br /> Department requirements <br /> Remarks/Sinnatures <br /> I The interpretations in this report represent our professional opinions and are based, in part, on information <br /> supplied by the client These opinions are based on currently available information and are arrived at in <br /> accordance with currently accepted hydrogeologic and engineering practices at this time and location <br /> Other than this, no warranty is implied or intended <br />' If you have any questions regarding this protect, please contact Katie Hickling at (916) 362-7100 <br /> Sincerely, <br /> IENSR Corporation <br /> xe..s <br />' Katie Hicklmg D N Peacock, PhD , P G #780 <br /> Project Manager Senior Project Manager <br /> KHldk DAVID N• <br /> a PEACOCtC <br /> cc Ms Amy Dietz, Norcal Waste Systems, Inc � �7801 0 <br /> Attachments <br /> CAL�� <br /> ENSRIAECOM <br />