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Third Quarter 2003, Groundwater Monitoring Report <br /> October 30, 2003 <br /> . Page 2 <br /> Number of Detections Minimum Maximum <br /> Constituents above the MDL of the 10 Concentration in prg/L(Well ID) Concentration in ug/L(Well ID) <br /> Total Samples <br /> TPHg 4 94(MW-6) 180(MW-5) <br /> Benzene 2 NO 0 6(MW-2 and Muni-10) <br /> MtBE 8 2(MW-4) 1,900(MW-1) <br /> Ethylbenzene 3 1 (Muni-10) 7(MW-5) <br /> Total xylenes 3 2(MW-2 and MW-5) 5(Muni 10) <br /> Definitions <br /> MDL=Method Detection Limit <br /> ,ug/L=Micrograms per Liter <br /> NO =Not Detected <br /> TBA, DIPE, ETBE, 1,2-DCA, and EDB were not detected in samples from any of the wells During <br /> the fourth quarter 2003, a groundwater confirmation sample will be collected from Municipal well # 10 <br /> and analyzed for TPHg, BTEX, and the fuel oxygenates MtBE, EtBE, DIPE, TAME, TBA, 1,2-DCA, <br /> EDB, and ethanol <br /> DISCUSSION (ARCO) <br /> On September 24, 2003, SECOR International Incorporated (SECOR) conducted groundwater <br /> monitoring and sampling for the third quarter 2003 ARCO station 2133, in conjunction with Gettler- <br /> Ryan performing groundwater monitoring and sampling for Chevron service station 9-4275 <br /> Nineteen ARCO wells were sampled during this event Groundwater samples were analyzed for <br /> TPHg, BTEX, and the fuel oxygenates MtBE, EtBE, DIPE, TAME, TBA, 1,2-DCA, EDB, and ethanol <br /> Groundwater elevations across the site decreased by an average of 1 78 feet A summary of <br /> laboratory data is listed below <br /> Number of Detections Minimum Maximum <br /> Constituents above the MDL of the 19 Concentration In prg/L(Well ID) Concentration in pg/L(Well ID) <br /> Total Samples <br /> TPHg 4 66(E-3) 6,200(E-10) <br /> Benzene 3 0 56(E-6) 240(E-10) <br /> MtBE 10 0 52(PR-1) 1,500 (E-10) <br /> Definitions <br /> MOIL=Method Detection Limit <br /> ,ug/L=Micrograms per Liter <br /> NO =Not Detected <br /> i <br /> Groundwater flow across both sites was to the south at an approximate gradient of 0 00 foot per foot <br /> (ft/ft) which is inconsistent with historical data Groundwater gradient has typically been to the north i <br /> across bath sites ARCO's groundwater elevation and analytical data are summarized in Tables 2 <br /> . and 4 Chevron's groundwater elevation and analytical data are summarized in Tables 1 and 3 <br /> Table 5 presents historical groundwater gradient data Groundwater concentrations for both sites <br /> 11Chevron1942751Periodic Monitoring\QMR1200312003 revised QMR Chev and Arcot doc <br />