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Ms. Lori Duncan S E C ® 1R <br /> May 6, 2005 <br /> Page 2 <br /> r� <br /> GROUNDWATER MONITORING DISCUSSION <br /> On March 7 and 8, 2005, SECOR conducted 1Q05 groundwater monitoring and sampling <br /> for CHEVRON service station 9-4275 and ARCO service station 2133. Nine monitoring <br /> wells were sampled at CHEVRON service station 9-4275, and seventeen monitoring wells <br /> were sampled at ARCO service station 2133. The City of Stockton Municipal District would <br /> not operate Municipal well #10, and would not allow SECOR to collect a sample during <br /> 1 Q05. Groundwater samples were analyzed for total petroleum hydrocarbons as gasoline <br /> (TPHg), benzene, toluene, ethylbenzene, and xylenes (BTEX), and the fuel oxygenates <br /> methyl-tertiary-butyl-ether (MtBE), ethyl-tertiary-butyl-ether (EtBE), di-isopropyl ether <br /> (DIPS), tertiary-amyl-methyl-ether (TAME), tertiary-butyl-alcohol (TBA), 1,2 dichloroethane <br /> (1,2 DCA), and 1,2 dibromoethane (EDB). A summary of laboratory data is listed below. <br /> CHEVRON <br /> Number of Detections Minimum Maximum <br /> Constituents above the MDL of the 9 Concentration,In N9.IL ell.ID Concentration'in fL. <br /> Total Samples Ing (Well ID) <br /> TPHg 3 58(MW-1) 2,100(MW-2) <br /> Benzene 1 ND 3(MW-2) <br /> MtBE 8 8(MW-4, MW-6,MW-7) 1,400(MW-3) <br /> Ethylbenzene 2 2(MW-5) 13(MW-2) <br /> Total xylenes 1 ND 5(MW-2) <br /> Definitions: <br /> MDL=Method detection limit <br /> NgIL=Micrograms per liter <br /> ND =Not detected <br /> ARCO <br /> lN, <br /> Number of Detections k r ? s <br /> above the ML]t_of the 77 Minimum Maximum <br /> Constituents concentratio <br /> TotalSamples n in NgIL(Well ID) Concentration in�rgli.(WelilD) <br /> TPHg 1 ND 160(E-10) <br /> Benzene 1 ND 1 (E-10) <br /> MtBE 4 0.52(PR-1) 3.8(E-10) <br /> Ethylbenzene 1 ND 0.79(E-10) <br /> Total xylenes 1 ND 1 A(E-10) <br /> Definitions: <br /> MDL=Method detection limit <br /> NgIL=Micrograms per liter <br /> ND =Not detected <br /> • <br /> t\Chevron1942751Periodic MonitoringlQ M R1200511Q05.doc <br />