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r <br /> ~ Bmwn and Caldwell <br /> Consultants <br /> 23 5 Street <br /> `.acranlcma <br /> F <br /> Cahlarnia 95a?4.7092 <br /> 9161 444•n123 <br /> ;ax 191614 <br /> July 16, 1990 <br /> Mr. Kyle Christie <br /> ARCO Products Company RECEIVED <br /> 2000 Alameda de las Pulgas J U L 2 Q M9 <br /> Post Office Box 5811 <br /> Sar. Mateo, California 94402 ENVIRONMW A1. tiEALTH017-3214-63 <br /> PERMIT/SERVICES <br /> Subject: Report on January 1490 Quarterly Groundwater Sampling <br /> at ARCO Station 434,501 Kettleman Lane, Lodi, California <br /> F <br /> f <br /> Dear Mr. Christie: <br /> This letter report describes the January groundwater sampling of eight on-and off-site monitoring <br /> wells at ARCO Products Company(ARCO) Station 434 in Lodi. A total of ten on- and off-site <br /> a groundwater monitoring wells (of which eight are monitored quarterly) were installed between <br /> April 1987 and June 1988. The purpose of the monitoring wells is to characterize hydrocarbon <br /> occurrence in groundwater beneath the site resulting from a December 1986 gasoline leak at <br /> Station 434. <br /> E Figure 1 shows the location of monitoring wells,benzene concentrations in groundwater samples <br /> collected from these wells during January 1990, groundwater contours, and the direction of <br /> groundwater flow. <br /> From April 1987 to January 1990, water levels in each well were measured monthly. The <br /> average depths to groundwater for each measuring event showed the groundwater to fluctuate <br /> from a high of 49 feet below ground surface in April 1987 to a low of 61 feet in August and <br /> September 1989. <br /> e Between July and November 1987, and again between May and July 1988, free product <br /> accumulated in monitoring wells W-2 and W-3. The maximum product thickness measured <br /> during these time periods was 3.18 feet of free product in monitoring well W-2. A total of 52 <br /> gallons of gasoline were recovered from these two wells during these two periods. Product has <br /> f <br /> not been detected in monitoring wells W-2 or W-3 since August 1988. <br /> To trace the dissolved hydrocarbon trends systematically, in the fall of 1988, ARCD authorized <br /> quarterly groundwater sampling and analysis for benzene, ethylbenzene, toluene, and xylene <br /> (BBTX). At the request of the California Regional Water Quality Control Board,Central Valley <br />