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itt l�� Chevron Products Company 2 Chevron Service Station 9-4275 _ __ July 31.2001 referenced site. Nine Chevron wells and Muni well# 10 were monitored and sampled during this event. Water level elevations measured during this monitoring event are summarized in Figure 2. During the second quarter,the groundwater gradient was to the southwest at 0.002 ft/ft. This is consistent with historical data. Groundwater samples were analyzed for total petroleum hydrocarbons quantified as gasoline(TPHg),benzene,toluene, ethylbenzene,and xylenes(BTEX),and the fuel oxygenates including methyl-tertiary-butyl-ether(MtBE),ethyl- tertiary-butyl-ether(EtBE),di-isopropyl ether(DIPE),tertiary-amyl-methyl-ether(TAME),tertiary-butanol(or tertiary-butyl-alcohol [TBA]), 1,2 dichloroethane(1,2 DCA), 1,2 dibromoethane(EDB),methanol, and ethanol. DIPE,ETRE, 1,2 DCA, and EDB were not detected in samples from any of the wells. TPHg was detected in samples collected from two wells at concentrations of 120 micrograms per liter(µg11) (MW-4) and 2,100µg11 (MW- 2) (Figure 3). Benzene was detected in the sample collected from one well (MW-2) at a concentration of NjAg/l.13 Toluene was detected in four wells sampled this quarter at concentrations ranging from 0.54µg11 (MW-5) to 0.64 gg/l (MW-4 and MW-9). Ethylbenzene was detected in samples collected from two wells at concentrations of 0.55 µg/1 (MW-5)and 24µg11(MW-2). Xylenes was detected in samples collected from three wells at concentrations of 0.63 µg11 (MW-5 and MW-4)and 3.4µg11(MW-2). MtBE was detected in samples from five wells at concentrations ranging from 0.78µg11 (MW-5)to 2,100µgll (MW-1) (Figure 4). TBA was detected in samples from two wells at concentrations ranging from 12µg/l (MW-2) to 64 µg/l (MW-4). TAME was detected in samples from three wells at concentrations ranging from 1.22 µg11 (MW-4)to 17 µg11(MW-1). Groundwater analytical data is summarized in Table 1 and Table 2. ATTACHMENTS: • Table I —Historical Groundwater Elevation and Analytical Data • Table 2—Groundwater Analytical Results—Oxygenate Compounds • Figure 1 --Site Location Map • Figure 2—Groundwater Elevation Contour Map • Figure 3—TPHg Isoconcentration Map,May 10,2001 • Figure 4—Benzene Isoconcentration Map,May 10,2001 • Figure 5—MtBE Isoconcentration Contour Map,May 10,2001 • Attachment A-Field and Laboratory Procedures • Attachment B -Field Data Sheets • Attachment C-Certified Laboratory Analytical Reports and Chain-of-Custody Documentation cc: Marty Hartzell,RWQCB-CVR,Sacramento,CA Bob Cochran,Chevron Products Company,San Ramon,CA _ 1:IChevron1942751Periodic Monitoring\Q M R12QMRO1.doc