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` r Chevron Products Company 2 Chevron Service Station 9-4275 Octoher 30 2001 • DISCUSSION: On August 20, 2001, SECOR conducted groundwater monitoring and sampling for the third quarter 2001 at the Arco station No. 2133 (2908 West Benjamin Holt Drive) and Chevron station 9-4275. Nine Chevron wells and municipal well No. 10 were sampled during this event. Arco wells were also sampled but this data is not included in this report;However Figures 2 and 3 summarizes groundwater elevations and dissolved concentrations at the Arco station No. 2133 for the third quarter 2001. Water level elevations measured during this monitoring event are summarized in Figure 2. During the third quarter,the calculated groundwater gradient flowed to the north ranging from 0.002 ft/ft to 0.004 ft/ft. This gradient 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). Benzene,Toulene,DIPE,ETBE, and EDB were not detected in samples from any of the wells. TPHg was detected in samples collected from four wells at concentrations ranging from 51 micrograms per liter(gg/L) (MW-4) to 170 gg/L(MW-2). Ethylbenzene was detected in the sample collected from MW-5 at a concentration of 0.95 gg/L. Xylenes was detected in the sample collected from MW-2 at a concentration of 0.61 gg/L. MtBE was detected in samples from six wells at concentrations ranging from 1.3 gg/L(MW-6) to 1,700 gg/L(MW-1). TBA was detected in samples from three wells at concentrations ranging from 9.9 gg/L (MW-4) to 110 gg/L(MW-1). TAME was detected in samples from three wells at concentrations ranging from 0.85 gg/L (MW-4) to 13 gg/L (MW-1). 1,2-DCA was detected in the sample collected from MW-9 at a concentration of 0.72 gg/L. Groundwater concentrations are summarized for TPHg,Benzene and MtBE in Figure 3. Groundwater analytical data is summarized in Table 1 and Table 2. ATTACHMENTS: . • Table 1 —Historical Groundwater EIevation and Analytical Data • Table 2—Groundwater Analytical Results—Oxygenate Compounds • Figure I —Site Location Map • Figure 2—Groundwater Elevation Contour Map,August 20,2001 • Figure 3—Groundwater Concentration Map, August 20,2001 • 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 1AChevron1942751Periodic Monitoring\Q M R13QMR01.doc