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S E C 0 R <br /> First Quarter 2004, Groundwater Monitoring Report <br /> April 30, 2004 <br /> Page 2 <br /> Number of Detections <br /> above the MDL of the 9 Minimum Maximum <br /> Constituents Total Samples Concentration in pg/L(Well ID) Concentration in pg/L(Well ID) <br /> TPHg 5 53(MW-4) 2,100(MW-2) <br /> Benzene 2 0 7(MW-5) 6(MW-2) <br /> MtBE 7 3(MW-7) 1 800(MW-3) <br /> Ethylbenzene 3 0 5(MW-1) 6(MW-2) <br /> Total xylenes 3 0 5(MW-5) 10(MW-2) <br /> Definitions <br /> MDL=Method Detection Limit <br /> pg/L=Micrograms per Liter <br /> ND =Not Detected <br /> GROUNDWATER MONITORING DISCUSSION (ARCO) <br /> On March 16, 2004, SECOR conducted 1Q04 groundwater monitoring and sampling for ARCO <br /> service station 2133, in conjunction with Gettler-Ryan performing groundwater monitoring and <br />�I sampling for CHEVRON service station 9-4275 Twenty wells were sampled during 1Q04 <br /> Groundwater samples were analyzed for TPHg, BTEX, and the fuel oxygenates MtBE, EtBE, DIPE, <br /> TAME, TBA, 1,2-DCA, EDB, and ethanol A summary of laboratory data is listed below <br /> Number of Detections Minimum Maximum <br /> Constituents above the MDL of the 20 Concentration in pg1L(Well ID) Concentration in pg1L(Well ID) <br /> Total Samples <br /> TPHg 6 63(E-6) 1 300(E-10) <br /> Benzene 1 ND 1 (E-9) <br /> MtBE 11 0 57(E-2) 770(E-10) <br /> Ethylbenzene 1 ND 3 6(E-9) <br /> Total xylenes 1 ND 11 (E-9) <br /> Definitions <br /> MDL=Method Detection Limit <br /> pg/L=Micrograms per Liter <br /> QUARTERLY RESULTS SUMMARY (CHEVRON & ARCO) <br /> Groundwater flow across both sites was to the north at an approximate gradient of 0 003 foot per <br /> foot (ft/ft) Groundwater gradient has typically been to the north across both sites A groundwater <br /> elevation contour map of the two sites is presented as Figure 2 Groundwater concentrations for <br /> both sites are summarized for TPHg, benzene, and MtBE in Figure 3 CHEVRON's and ARCO's <br /> groundwater elevation and analytical data is summarized in Tables 1 and 2, respectively <br /> CHEVRON's and ARCO's groundwater analytical data for oxygenated compounds is presented in <br /> Tables 3 and 4, respectively Historical groundwater gradient data is presented in Table 5 Field <br /> and laboratory procedures are presented in Attachment A CHEVRON's laboratory analytical <br /> results, chain-of-custody documents, and field data sheets are provided as Attachment B ARCO's <br /> laboratory analytical results, chain-of-custody documents, and field data sheets are provided as <br /> Attachment C <br /> 1 1Chevron1942751Periodic Monitonng\QMR1200411Q04 QMR doc <br />