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' 25 February 2005 • AGE-NC Project No 95-0104 Page 4 of 10 ethylbenzene and xylenes (BTEX) have not been detected in ground water samples collected from the site since June 2001 IFrom January 1995 to March 1997, dissolved 1,2-DCA concentrations at the site were as high as 540 µg/l (MW-1) 1,2-DCA was not analyzed in the ground water samples collected from the site between March 1997 and June 2001 Analysis of ground water samples for 1,2-DCA did resumed in June 2001 (Table 3) 1,2-DCA concentrations have been declining since the initiation of quarterly ground water monitoring The highest concentration of 1,2-DCA detected at the site over the past two years was 18 µg/l, detected in well MW-5 the closest down gradient well to the former UST area Concentrations of dissolved 1,2-DCA have migrated northeast, the consistent ground water flow direction at the site, toward and beyond MW-5 (Figure 6) It would appear that MW-5 has I become the location of the highest concentrations of dissolved 1,2-DCA and the core of the 1,2- DCA-impacted ground water Dissolved 1,2-DCA has been detected one or more times, since June 2001, notable in the samples collected from wells VW-1, MW-1, MW-5 and MW-6 1,2-DCA concentrations had not been detected in deeper-screened wells MW-2, MW-3 and MW-4 prior to the September 2004 sampling event 1,2-DCA was detected in well MW-4 at a low concentration of 0 83 µg/1, with the level of ground water only 3 15 feet above the screen interval of well MW-4 The vertical extent of 1,2-DCA-im acted ground water at the site appears to be defined outside of p the core area of contamination by wells MW-2, MW-3 and MW-4 However, the vertical extent is ' unknown in the area immediately down gradient of the former UST area and in the location of well MW-5 The lateral extent of 1,2-DCA-impacted ground water is undefined down-gradient of the former UST area beyond well MW-5 (Figures 5 and 6) ' WELL SURVEY-DOMESTIC WATER WELL DESTRUCTION Ground water samples collected from the domestic well located approximately one hundred-fifty to two hundred feet south(downgradient) of the former UST area in April 1993 contained substantial halogenated volatile organic compounds As a result, use of the domestic water well was discontinued in April 1993 In July 1996, the well was sealed and capped under a San Joaquin ' County permit AGE reviewed performed a door-to-door survey to determine the locations of water wells within a 2,000-foot radius of the subject property AGE representatives observed 58 private domestic water wells within a 2,000-foot radius of the site Well construction information was obtained from the State of California Department of Water Resources and interviews with property owners and tenants A domestic water well receptor is located approximately 250 feet northeast of the site in the down gradient direction While drinking water at and near the site is currently provided by the California Water Service Company(Cal Water),which maintains a municipal well and tank • approximately 2,000 feet north of the site between East Waterloo Road and Cherokee Road No Advanced CeoEnvironmental,Inc