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The Maximum Contaminant Level (MCL) for benzene, 1 µg/L, was exceeded in the groundwater <br /> sample collected from MW2 The MCL for MTBE, 13 gg/L, was exceeded in the groundwater <br /> samples collected from MW2 MW3, MW4, and MW7 The MCL for 1,2-DCA, 0 5 pg/L, was <br /> exceeded in the groundwater samples collected from all of the monitoring wells The California <br /> Drinking Water Action Level for TBA, 12 gg/L, was exceeded in the groundwater samples collected <br /> from MWI, MW2, MW6, and MW7 A summary of the laboratory analytical data is presented in <br /> Table 2 A copy of the laboratory analytical report is included in Attachment 2 An isoconcentration <br /> map depicting MTBE concentrations in the groundwater samples collected during the fourth quarter <br /> 2004 is shown on Figure 4 <br /> GEOTRACKER DATA UPLOAD <br /> The depth to water and the laboratory data was submitted electronically to the State Water Resources <br /> Control Board (SWRCB) Geotracker database (confirmation numbers 6412479996 and 4019370734, <br /> respectively) Documentation of the data submittal is contained in Attachment 3 <br /> CONCLUSIONS <br /> Groundwater flow direction and gradient are generally consistent with previous sampling events <br /> Water table elevations have decreased since the July 2004 monitoring event The laboratory <br /> . analytical results of the groundwater samples collected from MW1, MW2, MW4, MW6, and MW7 <br /> are generally similar to the results of the groundwater samples collected from these wells in July <br /> 2004 The laboratory analytical results of the groundwater samples collected from MW3 and MW5 <br /> generally indicate reduced concentrations of detected constituents with respect to the samples <br /> collected from these wells in July 2004 <br /> RECOMMENDATIONS <br /> Based on the results of the fourth quarter 2004 monitoring event, we recommend continued quarterly <br /> groundwater monitoring The next quarterly sampling event is scheduled for January 2005 <br /> Please contact our office at(209) 579-2221 if you have any questions or comments <br /> Respectfully submitted, <br /> ATC Associates Inc <br /> aa� i C Hk' GI/ <br /> Todd Hafner � `�� s s� <br /> Project Geologist <br /> * <br /> No. 4450 � <br /> Lorraine M Sawyer, R G v',. p•a•`--�'�� 1Q' <br /> CA Registered Geologist No 4450 <br /> WF +CAk%t <br /> cc Mr Robert Eggiman <br /> Jim Barton, RWQCB <br /> S lenvirorunentail224931Reportsl4QR-04 doe 4 <br />