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1 <br /> EPRIt <br /> 1 <br /> • Mr Jeff Wong <br /> 1 February 16, 2005 <br /> Page 2 <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 2004 is <br />' included as Figure 4 A copy of the certified laboratory analytical report with chain-of-custody <br /> documentation is included in Attachment C <br /> Well Survev <br /> All groundwater monitoring wells were surveyed by Morrow Surveying in accordance with State <br />' of California Assembly Bill AB2886 on December 1, 2004 The top-of-casing elevation and the <br /> adjacent ground surface elevation were surveyed relative to mean sea level within 0 01 foot for <br /> each well A copy of the well survey conducted on December 1, 2004 is included in <br /> Attachment D <br />' Conclusions/Recommendations <br />' MW-1 has not had any reportable concentrations of petroleum hydrocarbon constituents for <br /> over ten years Reported concentrations in MW-2 have significantly decreased since the <br /> previous (third quarter 2004) monitoring event Reported concentrations in MW-3 have also <br /> decreased since the third quarter 2004 event to below the laboratory reporting limits TPHd <br /> decreased to below the laboratory reporting limits in MW-4 Based on the systematic <br /> demonstrated attenuation through time in concentrations of the chemicals of concern, <br /> groundwater at this site does not pose a threat to human health or the environment, and in our <br /> opinion, this site should be closed <br /> Future Work <br /> Mr Mark Naugle of ENSR discussed site closure with Mr Jeff Wong of the San Joaquin County <br /> Public Health Services Department during a telephone conversation on December 15, 2004 <br /> During this conversation, Mr Wong indicated that quarterly groundwater monitoring should <br /> continue and that he should be notified at least 48 hours before the next event The next <br /> quarterly groundwater monitoring and sampling event is scheduled for February 2005 <br /> • J 1Projects10502A031\Worlung\Reports105027-0314th Qtr 04-QMR doc <br /> Celebrating 35 Years of Excellence in Environmental Services <br />