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r <br /> (1j <br /> Mr Martin Harris <br /> Page 3 of 3 <br /> • No benzene or toluene was detected in any site well in March 2004 Ethylbenzene and xylenes were <br /> detected only to well MW1, at concentrations of 38 gg/L and 37 gg/L, respectively <br /> Methyl-tert butyl ether (MTBE) was detected in wells MW I, MW3 and MW5 at concentrations of 5 0 <br /> pg/L, 12 gg/L and 3 1 gg/L, respectively No MTBE was detected above the method detection limit <br /> (MDL) of 2 0 gg/L in wells MW2, MW4, MW6 or MW7 No other oxygenated gasoline additives or <br /> lead scavengers were detected in any site well Analytical results are summarized in Table 2 <br /> Attachment B contains the Iaboratory report and chain of custody documentation Charts showing <br /> contaminant concentration trends are included in Attachment C <br /> SUMMARY AND CONCLUSIONS <br /> Shallow groundwater beneath the site rose an average of 0 63 feet between December 16, 2003 and <br /> March 12, 2004 Groundwater on March 12, 2004 generally flowed to the northwest at a relatively flat <br /> gradient of approximately 7 to 12 ft/mile, although the calculated groundwater elevation in well MW7 is <br /> somewhat anomalous compared to other site wells <br /> Low levels of TPHg were detected in wells MWI and MW7 and low levels of ethylbenzene and xylenes <br /> were detected only in well MW 1 No Benzene or toluene were detected in any site well MTBE was <br /> detected only in wells MW 1, MW3, and MW5, ranging from 3 1 p,g/L (MW5) 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 gg/L) since March 2003 Currently, only one well (MW3) contains MTBE at levels <br /> exceeding the secondary MCL of 5 gg/L <br /> RECOMMENDATIONS <br /> Quarterly groundwater sampling of site wells should continue to monitor MTBE concentrations in <br /> downgradient wells MW3 and MW5 In addition, the wells should be re-surveyed to investigate the <br /> apparent anomalous groundwater elevation data in well MW7 <br /> Copies 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, � ReD <br /> Ground Zero Analysis, Inc <br /> LA"" <br /> John P Lane U�Y <br /> No 6/95 <br /> e <br /> CA Registered Geologist No 6795 '<'' O <br /> Op CP, <br /> Attachments <br /> G1GROUNDZE\TuftBoN\Reports\QMR\IQM2004 doc <br />