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u <br /> PUBLIC tALTH SERVIttS <br /> p,qU►N <br /> SAN JOAQUIN COUNTY i z: <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 9JT02 D qc►Fo���P <br /> 209/468-3420 O <br /> MAR 17 JM <br /> US RENTALS <br /> 2081 E CHARTER WY <br /> STOCKTON, CA 95205 Site code: 2223 <br /> Re: US Rentals, 1444 Mariposa Rd.,Stockton, CA 95205 <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) <br /> has reviewed the quarterly monitoring report prepared by Wallace-Kuhl & Associates <br /> dated November 12, 1997 for the above referenced site. <br /> Ground water has risen over the tops of the monitoring well screen interval. Therefore, <br /> results of the past four quarterly sampling events may not represent groundwater <br /> conditions. <br /> A review of soil sample results for the site indicates the deepest soil sample was taken at <br /> 81 feet in 1993. Sample results were .017parts per million (ppm) benzene, .012 ppm <br /> toluene and .0076 ppm xylene. Since no deeper investigative work has been done, the <br /> vertical extent of contamination is unknown at this site. San Joaquin County Public <br /> Works Flood maps for 1977 showed groundwater in this area to be at about 80 feet below <br /> fie• <br /> The three monitor wells were installed from 100 feet to 200 feet from the underground <br /> tank locations, so monitoring data closer to the source of contamination doesn't exist. <br /> The monitor wells are screened from 64 feet to 84 feet below grade. Even with these <br /> conditions groundwater contamination was evidenced in 1996 when groundwater was at <br /> 62 feet below grade. <br /> The groundwater gradient has shown a fluctuation from a southwest direction in October <br /> 1993 to the northwest in August 1996 to east in November 1997. The reason for this <br /> divergent gradient has not been clarified. <br /> Review of file documents for this site reveals that an over-excavation of contaminated <br /> soil occurred on November 9, 1992. As per information received from Matt Taylor during <br /> the recent February 25, 1998 quarterly sampling, contaminated soil from over-excavation <br /> on November 9, 1992, at this site was removed off site. No documentation of the soil <br /> disposal has been received by PHS/EHD. <br /> A soil vapor extraction system was planned for this site. The current plan for continued <br /> contamination investigation and remedial action for this site is unknown. <br /> A Division of San Joaquin County Health Care Services <br />