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Mr Martin Harris <br /> Page 3 of 3 <br /> TPHg was detected in wells MW2 and MW7 at concentrations of 57 micrograms per liter (VL / ) and 170 <br /> gg/L, respectively No TPHg was detected in wells MWI, MW3, MW4, MW5, or MW6 <br /> No benzene or toluene was detected in any site well in June 2004 Ethylbenzene was detected in wells <br /> MW2 and MW7 at concentrations of 0 7 }tg/L and 0 8 µg/L, respectively Xylenes were detected only in <br /> well MW7, at a concentration of 1 6 p,g/L <br /> MTBE was detected in wells MW1, MW3 and MW5 at concentrations of 6 7 pg/L,, 12 µg/L and 7 2 µg/L, <br /> respectively No MTBE was detected above the method detection limit (MDL) of 2 0 µg/`L in wells <br /> MW2, MW4, MW6 or MW7 No other oxygenated gasoline additives or lead scavengers were detected <br /> in any site well Analytical results are summarized in Table 2 Attachment B contains the laboratory <br /> report and chain of custody documentation Charts showing contaminant concentration trends are <br /> included in Attachment C <br /> SUMMARY AND CONCLUSIONS <br /> Shallow groundwater beneath the site fell an average of 0 46 feet between March 12, 2004 and June 29, <br /> 2004 Groundwater on June 29, 2004 generally flowed to the west-northwest at a relatively flat gradient <br /> of approximately 4 3 ft/mile <br /> Low Ievels of TPHg and ethylbenzene were detected in wells MW2 and MW7 and low levels of xylenes <br /> were detected only in well MW7 No Benzene or toluene was detected in any site well MTBE was <br /> detected only in wells MW1, MW3, and MWS, ranging from 6 7 [&L (MW1) to 12 gg/L (MW3) No <br /> site monitoring well has contained MTBE at concentrations exceeding the California primary MCL for <br /> drinking water (13 pg/L) since March 2003 Currently, wells MW1, MW3 and MW5 contain MTBE at <br /> levels exceeding the secondary MCL of 5 pg/L <br /> RECOMMENDATIONS <br /> Quarterly groundwater sampling of site wells should continue to monitor MTBE concentrations in <br /> downgrad►ent wells MW3 and MW5 <br /> A copy of this report should be forwarded to Ms Lori Duncan of EHD and Mr James L L Barton of the <br /> California Regional Water Quality Control Board, Central Valley Region (RWQCB) <br /> Please feel free to contact Ground Zero at (209) 838-9888 should you have any questions regarding this <br /> submittal <br /> Respectfully, ����`�B G{p <br /> Ground Zero Analysis, Inc"4� 4 <br /> o IrnttE o <br /> John P Lane I•o 6j'95 <br /> CA Registered Geologist No 6795 <br /> Attachments <br /> G\GROUNDZE\Tti Boy\RcportclQMR12QN12004 dui <br />