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Tracy Well Survey -5- 28 December 1995 <br /> RWQCB <br /> Table 1). The highest concentration of chloroform was detected at 2040 µg/1 in the sample from <br /> MW-4A(see Table 1). <br /> Ground water monitoring reports from WESTON indicate that, since April of 1990, with the <br /> exception of the February 1992 sampling round, chloroform concentrations have been consistently <br /> detected in excess of the State MCL of 100 µg/1 in samples from monitoring well TEP-MW4A <br /> (Table 4). <br /> Figure 6 graphically displays the concentrations of chloroform detected in ground water samples <br /> from the Triple E Produce monitoring wells during the survey period. This data was compiled <br /> from Triple E Produce Monitoring Reports completed by Weston. <br /> Lyoth Loading Station <br /> The Lyoth Loading station is a former Chevron bulk fuel loading station, located directly east of <br /> the DDRW Tracy facility and northwest of the All Pure Chemical Co.(Figure 1). <br /> The Lyoth Loading station has two monitoring wells(MW-1 and MW-2) on site (see site map - <br /> Figure 8). These wells are screened within the upper horizon at an interval from 11 to 26 feet <br /> bgs. <br /> Both monitoring wells were sampled by Regional Board staff during December of 1992. No <br /> VOC contamination was detected in MW-1. MW-2 contained petroleum contamination which <br /> created masking affects during the analytical procedures resulting in a detection limit for CC14 of <br /> 200 pg/l. Because of this increased detection limit, results were inconclusive regarding the <br /> presence of carbon tetrachloride or chloroform contamination in the ground water samples <br /> collected from MW-2 at this site. <br /> CONCLUSIONS <br /> Carbon tetrachloride contamination <br /> The data evaluated indicates that a plume of CC14 ground water contamination exists along a <br /> north-south path in the vicinity of South Banta Road. Concentrations are highest in ground water <br /> analyzed from wells at the All Pure Chemical site and decrease in ground water wells to the north. <br /> Since 1991, the concentration of CC14 in ground water at APC appears to have increased <br /> considerably. <br /> Based on the local gradient and the distribution of carbon tetrachloride concentrations in ground <br />