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Second Quarter 2003, Groundwater Monitoring Report <br /> July 30, 2003 <br /> Page 2 <br /> I <br /> Number of Detections Minimum Maximum <br /> Constituents above the MDL of the 9 Concentration in p911-(Well ID) Concentration in pg/L(Well ID) <br /> Total Samples <br /> TPHg 3 52(MW-6) 1,300(MW-2) <br /> Benzene 1 ND 2(MW-2) <br /> MtBE 5 3(MW-5) 3,200(MW-1) <br /> Ethylbenzene 1 ND 7(MW-2) <br /> xylenes 1 ND 10(MW-2) <br /> Toluene 1 ND 0 6(MW-6) <br /> TAME 2 2(MW-9) 41 (MW-1) <br /> Definitions <br /> MDL=Method Detection Limit <br /> uglL=Micrograms per Liter <br /> ND =Not Detected <br /> DISCUSSION (ARCO) <br /> On June 17 and 18, 2003, SECOR International Incorporated (SECOR) conducted groundwater <br /> monitoring and sampling for the second quarter 2003 ARCO station 2133, in conjunction with <br /> Gettler-Ryan performing groundwater monitoring and sampling for Chevron service station 9-4275 <br /> Nine ARCO wells were sampled during this event Groundwater samples were analyzed for total <br /> petroleum hydrocarbons quantified as gasoline (TPHg), benzene, toluene, ethylbenzene, and <br /> xylenes (BTEX), and the fuel oxygenate methyl-tertiary-butyl-ether (MtBE) Groundwater elevations <br /> across the site decreased by an average of 0 24 feet A summary of laboratory data is listed below <br /> Number of Detections Minimum Maximum <br /> Constituents above the MDL of the 9 Concentration In pg1L(Weil ID) Concentration In pg/L(Well ID) <br /> Total Samples <br /> TPHg 1 ND 170(E-10) <br /> Benzene 1 ND 3 7(E-10) <br /> MtBE 2 250(BHD-1) 290(E-10) <br /> Definitions <br /> MDL=Method Detection Limit <br /> ug/L=Micrograms per Liter <br /> ND =Not Detected <br /> Groundwater flow across both sites was to the north at an approximately gradient of 0 002 foot per <br /> foot (ft/ft), which is generally consistent with historical data ARCO's groundwater elevation and <br /> analytical data are summarized in Table 2 Chevron's groundwater elevation and analytical data are <br /> summarized In Tables 1 and 3 Table 4 presents historical groundwater gradient data A <br /> groundwater elevation contour map of the two sites Is presented as Figure 2 Groundwater <br /> concentrations for both sites are summarized for TPHg, benzene, and MtBE in Figure 3 Attachment <br /> 1 contains ARCO's historical SVE and recent AS system operational data Attachment 2 contains <br /> I IChevron1942751Periodic Monitoring\QMR1200312003 revised QMR Chev and Arcoi doc <br />