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Date July 31, 2002 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No: 5469 Address: 130 South Wilson Way, Stockton, California <br /> ARCO Environmental Engineer: Paul Supple <br /> Consulting Co./Contact Person: Stratus Environmental, Inc. 1 Jay R. Johnson <br /> Consultant Project No: U5469-04-3 <br /> Primary Agency/Regulatory ID No: Rebecca Setliff, San Joaquin County Public Health Services <br /> WORK PERFORMED THIS QUARTER (Second 2002): <br /> 1. Groundwater samples were collected from monitoring wells MW-1 through MW-10 and submitted for <br /> laboratory analysis. <br /> 2. Groundwater monitoring data was compiled and evaluated. <br /> WORK PROPOSED FOR NEXT QUARTER (Third 2002): <br /> 1. Quarterly groundwater monitoring and sampling will continue at the site. The next sampling event is <br /> tentatively scheduled for August 2002. Groundwater samples will be collected from monitoring wells <br /> MW-1 through MW-10 and analyzed for total petroleum hydrocarbons as gasoline (TPHG), benzene, <br /> toluene, ethylbenzene, and total xylenes (BTEX) using USEPA Method 8015/8020 DHS LUFT, and for <br /> tertiary butyl alcohol (TBA), methyl tertiary butyl ether (MTBE), di-isopropyl ether (DIPE), ethyl tertiary <br /> butyl ether (ETBE), tertiary amyl methyl ether (TAME), 1,2-Dichloroethane (1,2-DCA), and ethylene <br /> dibromide (EDB) using USEPA Method 8260B. <br /> Current Phase of Project: Monitoring <br /> Frequency of Groundwater Sampling: All Monitoring Wells=Quarterly <br /> Frequency of Groundwater Monitoring: Quarterly <br /> Sampling Date: Aril 23,2002 <br /> Is Free Product(FP) Present on Site: No <br /> FP Recovered This Quarter: N/A <br /> Cumulative FP Recovered to Date: NIA <br /> Approximate Depth to Groundwater: 39.69 to 40.51 feet bgs <br /> Groundwater Flow Direction: Northeast <br /> Groundwater Gradient: 0.0017 <br /> DISCUSSION: <br /> MTBE was detected in groundwater samples collected from wells MW-1, MW-3 through MW-8, and <br /> MW-10. TPHG and benzene were detected in the sample collected from wells MW-3 (78 µg11 and 1.5 <br /> µg11), MW-4 (11,000 pgll and 4,700 µg11), and MW-8 (27,000 µg11 and 16,000 µg/1). TPHG was also <br /> detected in samples collected from well MW-9 (59 pg/1). Benzene was also detected in samples collected <br /> from wells MW-5 (2.9 µg11) and MW-10 (1.2 pg/1). 1,2-DCA was detected in the samples collected from <br /> P:1Bp-Arco for URS\5469\Quarterly\Arco_5469_2Q02.doc Stratus <br />