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Fourth Quarter 2003, Groundwater Monitoring Report <br /> January 30, 2004 <br /> Page 2 <br /> t <br /> Number of Detections Minimum Maximum <br /> Constituents above the MDL of the 9 Concentration in yg1L(Well ID) Concentration in yg/L(Well ID) <br /> Total Samples <br /> TPHg 3 290(MW-1) 1,400(MW-5) <br /> Benzene 2 ND 2(MW-2 and MW-5) <br /> MtBE 7 8(MW-4) 1,400(MW-1) <br /> Ethylbenzene 3 0 8(MW-1) 57(MW-5) <br /> Total xylenes 2 19(MW-5) 29(MW-2) <br /> Definitions <br /> MDL=Method Detection Limit <br /> yg/L=Micrograms per Liter <br /> ND =Not Detected <br /> GROUNDWATER MONITORING DISCUSSION (ARCO) <br /> On December 18, 2003, SECOR conducted 4Q03 groundwater monitoring and sampling for Arco <br /> service station 2133, in conjunction with Gettler-Ryan performing groundwater monitoring and <br /> sampling for Chevron service station 9-4275 SECOR's request for a reduction from quarterly to <br /> semi-annual sampling of wells E-2, E-8, E-11 and E-12, a reduction from quarterly to annually <br /> sampling of wells MW-4 and MW-5, and a reduction from semi-annual to annual sampling of wells E- <br /> 7, PR-2, BHD-2, MW-2, and MW-3 was approved by the San Joaquin County, Environmental Health <br /> Department (SJC/EHD) as stated In the letter presented in Attachment E Therefore, five Arco wells <br /> (E-8, E-9, E-10, PR-1, and BHD-1) were sampled during 4Q03 Groundwater samples were <br /> analyzed for TPHg, BTEX, and the fuel oxygenates MtBE, EtBE, DIPE, TAME, TBA, 1,2-DCA, EDB, <br /> and ethanol Groundwater elevations across the site increased by an average of 061 feet A <br /> summary of laboratory data is listed below <br /> Number of Detections Minimum Maximum <br /> Constituents above the MDL of the 5 Concentration In yg/L(Well ID) Concentration in yg1L(Well ID) <br /> Total Samples <br /> TPHg 4 60(E-8) 3,300(E-10) <br /> Benzene 2 1 2(E-9) 78(E-10) <br /> MtBE 5 0 52(PR-1) 1,100(E-10) <br /> Ethylbenzene 2 3 4(E-9) 54(E-10) <br /> Total xylenes 2 7(E 9) 220(E-10) <br /> Definitions <br /> MDL=Method Detection Limit <br /> ug/L=Micrograms per Liter <br /> QUARTERLY RESULTS SUMMARY (ARCO & CHEVRON) <br /> Groundwater flow across both sites was to the north at an approximate gradient of 0 002 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 /> 11Chevron1942751Periodic Monitoring\QMR1200314003 revised QMR Chev and Arcoll doc <br /> 1 <br />