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.d <br /> PRELIMINARY INVESTIGATION AND EVALUATION REPORT <br /> San Joaquin Marketing Association <br /> 1750 East Channel Street <br /> Stockton, California <br /> 1.0 INTRODUCTION <br /> In April 1993 , Mr. Herman Campora of the San Joaquin Marketing <br /> Association (SJMA) retained Geological Audit Services, Inc. <br /> J (GeoAudit) to prepare a Site Contamination Workplan for the <br /> property located at 1750 East Channel Street, Stockton, California <br /> (the site) . The location of the site is illustrated on Figure 1. <br /> The workplan was approved by the San Joaquin County Public Health <br /> J <br /> Services / Environmental Health Division (PHS/EHD) in June, and <br /> GeoAudit was retained to perform the work specified in the <br /> workplan. <br /> The assessment. performed on June 23, 1993 , consisted of the <br /> drilling of one boring near the center of the former underground <br /> storage tank excavation. This report presents the results of this <br /> assessment. <br /> 2. 0 BACKGROUND <br /> The site is located in a flat industrial/commercial area of central <br /> Stockton (Figure 1) . The site is underlain by unconsolidated <br /> Quaternary alluvial sediment consisting mostly of clayey silt to <br /> sandy silt. Groundwater is reported to be at 65-70 feet below <br /> surface grade in monitoring wells on a nearby property. Seasonal <br /> high groundwater is estimated to be approximately 45 to 50 feet <br /> below grade. <br /> In October of 1986, three underground storage tanks (UST's) were <br /> removed from the site: (1) 10, 000-gallon diesel tank; (1) 2 , 000- <br /> gallon regular leaded tank; and (1) 1, 500-gallon regular leaded <br /> tank. Soil samples collected from beneath the tanks indicated that <br /> contamination was present. Total extractable petroleum hydrocarbons <br /> (TEPH) were detected at concentrations as high as 3 , 000 ppm. Total <br /> lead was detected at concentrations as high as 65 ppm. <br /> Contamination was centered beneath the middle tank. A site plan <br /> with the boring location is illustrated on Figure 2 . On March 9, <br /> 1993 , San Joaquin County PHS/EHD informed SJMA that an assessment <br /> of the vertical and lateral extents of soil contamination at this <br /> site would be required. <br /> 1 <br /> .J <br />