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1 a , <br /> Mr Harlin Knoll <br /> Page 2 of 2 <br /> • <br /> ANALYTICAL RESULTS <br /> Well MWI contained TPHg at a concentration of 240 parts per billion (ppb), benzene at 1 7 ppb, <br /> ethylbenzene at i 1 ppb, and xylenes at 5 4 ppb Well MW5 contained TPHg at a concentration of 27,000 <br /> ppb, benzene at 2,000 ppb, toluene at 1,200 ppb, ethylbenzene at 1,100 ppb, and xylenes at 5,800 ppb No <br /> gasoline constituents were detected in wells MW4, or MW9 Analytical results are summarized in Table <br /> 3 Laboratory data sheets and chain of custody documentation are included in Attachment B Figure 3 <br /> presents a benzene isoconcentration map utilizing the most recent analytical results Attachment C <br /> contains graphical representations of TPHg and benzene concentrations over time in site wells <br /> SUMMARY <br /> Groundwater beneath the site during the reporting period ranged from approximately 36 10 to 37 68 feet <br /> btoc and generally flowed east-northeast The potentiometric surface at the site fell an average of 0 51 feet <br /> between February 19, 2003 and May 12, 2004 The water level currently lies above the screened interval <br /> in wells MW4 and MW5 Gasoline constituents were detected at elevated levels in well MW5 and at <br /> relatively low levels in well MWI No gasoline constituents were detected in wells MW4, or MW9 <br /> Contaminant concentrations in well MW5 have exhibited a declining trend since December 1996 <br /> RECOMMENDATIONS <br /> Since contaminant concentrations in well MWS continue to decline and the lateral extent of groundwater <br /> contamination has been defined, Ground Zero makes the following recommendations <br /> I Reduce the sampling frequency of well MW3 from semi-annual to annual, <br /> 2 Reduce the sampling of wells MWI, MW4, and MW9 from quarterly to annual <br /> Ground Zero would continue to sample well MW5 on a quarterly basis The groundwater elevations <br /> would also be monitored quarterly Wells MWI, MW2, MW3, MW4, and MW9 would be sampled <br /> annually <br /> I <br /> Please contact John Lane at(209) 838-9888 if you have any questions or comments regarding this report <br /> Respectfully, - <br /> Ground Zero Analysis, Inc si 4'V <br /> EIJ GFO�O <br /> a� JO min <br /> NIS P � <br /> John P Lane Lr;l~i <br /> CA Registered Geologist 6795 tn, No 6795 <br /> Attachments <br /> C!� <br /> cc Mr Carl Knowles <br /> Mr Patrick D Riddle, Attorney at Law <br /> Mr James L L Barton, CRWQCB <br /> G 1GROUNDMEIKNOWLES HAMIREPORTSkQMR12004QQM2004 doe <br />