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r i <br /> Mr Harlin Knoll <br /> November 14, 2000 <br /> Page 4 of 4 <br /> toluene were detected in the sample collected from well MW3 No gasoline constituents were <br /> detected in the samples collected from wells MW2, MW4, or MW8 <br /> Well MW5 contained TPI-Ig at 46,000 parts per billion (ppb) and benzene at 7,600 ppb, MW1 <br /> contained TPI-Ig at 610 ppb, and benzene at 13 ppb, and MW3 contained toluene at 0 8 ppb <br /> Figure 3 presents a benzene isoconcentration map from the third quarter analytical results, <br /> including the grab groundwater sample collected from boring SBTX located north of well MW5 <br /> Analytical results are summarized in Table 4 Laboratory data sheets and chain of custody <br /> documentation are included in Attachment D Attachment E contains graphical representations of <br /> TPHg and benzene concentrations over time in each site well <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> Soil in the vicinity of boring SB1X has not been impacted by the release of petroleum <br /> hydrocarbons from the former USTs at the Knowles Store Boring SB1X essentially represents <br /> the northern extent of the dissolved gasoline plume resulting from the former USTs <br /> TPI-Ig and benzene levels in well MW5 have decreased approximately 76% since their recorded <br /> high in December 1996, and contaminant concentrations in well MWI have decreased more than <br /> 94% from the recorded highs in that well <br /> Ground Zero recommends considering historical site data, including the extent of soil and <br /> groundwater contammation, historical trends in contaminant concentrations versus time, relative <br /> plume stability, and the infeasibility of additional remedial action to evaluate if the site should be <br /> closed as a low-nsk contamination case <br /> Please contact John Lane at (209) 838-9888 if you have any questions or comments regarding this <br /> submittal <br /> Sincerely, �A�D GF��O <br /> Ground Zero Analysis, Inc C <br /> Q JOHN P <br /> 0 <br /> LANE o <br /> No 6795 <br /> John P Lane <br /> CA Registered Geologist 6795 P <br /> JPL <br /> Attachments <br /> cc Mr Marty Harzell, CRWQCB Sacramento <br /> Mr Carl Knowles <br /> Mr Patrick D Riddle, Esq <br /> Knowles l,amlrapmt0gm20W dw <br />