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S E C ® R <br /> . Mr Harlin Knoll <br /> January 18, 2006 <br /> Page 4 sr <br /> these constituents rapidly decrease after May 2002 Benzene has not been detected in <br /> either of these wells since October 2002 The most recent detections of MtBE occurred <br /> during the October 26, 2005 sampling event, In wells MW-3 and MW-4, at concentrations of <br /> 100 pg/L and 6 pg/L, respectively It is plausible these "spikes" represent when residual <br /> hydrocarbon material, released during tank removal, came into contact with groundwater <br /> Evidence for this exists in the definite time lag between concentrations peaking in the <br /> upgradlent well, approximately two years before the peak occurs in the downgradient well <br /> and is supported by similarity in trends between constituent concentrations in individual <br /> wells <br /> RECOMMENDATIONS <br /> It appears that only low level concentrations of residual petroleum hydrocarbons remain in <br /> the areas of the former UST pit and downgradient of the former UST excavation In <br /> addition, benzene has not been detected in either of these wells since October 2002 MtBE <br /> has been consistently detected in both MW-3 and MW-4, but the concentrations of this <br /> constituent continues to approach its primary MCL of 13 pg/L <br /> . In light of the above information, Chevron and SECOR would like to arrange a meeting with <br /> representatives of the San Joaquin County Environmental Health Department (EHD) in <br /> early 2006 to discuss future activities at the site Specifically, Chevron and SECOR would <br /> like to consider the possibility of submitting a no further action request for the site <br /> If you have any questions or concerns regarding this report, please feel free to contact <br /> George Forsythe at (559) 271-2650, ext 235 <br /> Sincerely, <br /> SECOR International Incorporated <br /> ED GEC< <br /> �C`�'�� Fogs <br /> Georg Forsythe P * " No Irmn <br /> Senior Geologist EV <br /> u� �Q <br /> -9j�OF CA`,�DQ� <br /> N IFdes\Projects\Chevron\Retaill#9-82641Penodic 1V1orntonng=0514QMR0514Q2005 QMR doc <br />