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S E C 0 R <br /> . Mr Harlin Knoll <br /> March 27, 2006 <br /> Page 3 <br /> Detected constituents In groundwater are summarized below <br /> Number of Detections Minimum Reported Maximum Reported <br /> Constituents Above the MDL Concentration in,ag/L Concentration in pg/L <br /> Total Samples Collected =10 (Well ID) (Well ID) <br /> TPHg 5 <50 13,000 (MW-4D) <br /> Benzene 3 <0 5 890 (MW-4D) <br /> MtBE 3 <0 5 56 (MW-3) <br /> 1,2-DCA 4 <0 5 2 (MW-2) <br /> EDB* 0 <0 5 <1 (MW-4D) <br /> EXPLANATION <br /> MDL=Method detection limit <br /> ,vg/L=Micrograms per liter <br /> TPHg=Total petroleum hydrocarbons as gasoline <br /> MtBE=Methyl tert-butyl ether <br /> 1,2-DCA= 1,2-dichloroethane <br /> EDB=Ethylene dibromide <br /> 'Note The MDL for EDB at MW-41D was increased to"1"as the laboratory dilution factor increased to 2" <br /> CONCLUSIONS <br /> Historical groundwater monitoring data indicates that concentrations of TAME have not <br /> been at or above the MDL since sampling began In 1998 In groundwater monitoring wells <br /> MW-1, MW-2, MW-4, MW-5, MW-513, MW-6, MW-6D, and MW-7 TAME was detected In <br /> MW-3 at 2 6 Ng/L in February 2001 and In MW-4D during three consecutive monitoring <br /> events of May, June and October 2003 with concentrations of 11 Ng/L, 5 Ng/L and 3/,Jg/L, <br /> respectively However, prior to and following these detections, TAME concentrations have <br /> been below the MDL Furthermore, there are no detections of ethanol, DIPE, and EtBE at <br /> or above their respective MDLs In any of the site monitoring wells since sampling began in <br /> 1998 <br /> At the request of the County, EDB and 1,2-DCA were recently added to the sampling <br /> protocol EDB was not detected in any groundwater samples collected during this quarter <br /> 1,2-DCA was detected in wells MW-2, MW-5, MW-6, and MW-7 at concentrations of 2 ug1L, <br /> 0 5,ug/L, 3 erg/L, and 0 7 pg/L, respectively Monitoring wells MW-2 and MW-6 exceed the <br /> primary maximum contaminant level (MCL) of 0 5 �ugIL as established by the California <br /> Department of Health Services (DHS) Monitoring well MW-7 only slightly exceeds the <br /> MCL and monitoring well MW-5 Is at the MCL <br /> N 1FileslProjects\Chevron\Retaill#9-32321Penodic Monitonng1200611Q0611Q06 QMR doe <br />