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SOIL BORING INSTALLATION <br /> 1549 East Channel Street <br />' Stockton, California <br /> SITE DESCRIPTION <br /> IThe site is located in a flat light-industrial/commercial area of <br /> central Stockton (Figure 1 - Location Map, 7 . 5 Minute Stockton West <br />' Quadrangle, USGS Topographic Map Series, 1987) . The site is <br /> currently vacant. <br /> The site is underlain by unconsolidated Quaternary alluvial <br /> sediment. The upper twenty feet consists of clayey sands to silty <br /> sands. Groundwater was not encountered in this investigation, but <br /> is more than 60 feet below surface grade. <br /> PREVIOUS WORK <br /> According to existing records, one 8, 000 gallon diesel tank and one <br /> 10, 000 gallon diesel tank were removed from the site on 7 October <br /> 1988 . Soil contamination was encountered during the tank removal. <br /> The contaminated soil was excavated from the tank cavity and <br /> stockpiled adjacent to the cavity. The stockpiles were <br /> characterized and transported to a licensed disposal facility (see <br /> GeoAudit Stockpiled Soil Removal Report of 16 November 1992) . <br /> I �—On 12 July a 1, 000 gallon gasoline tank was removed from the <br /> site. According to information provided to the SJ PHS/EHD, soil <br /> samples collected from beneath the tank showed detectable levels of <br /> total petroleum hydrocarbons (TPH as gasoline at 6, 100 ppm) and <br /> purgeable aromatics (benzene at 11. 5 ppm; toluene at 430 ppm; <br /> ethylbenzene at 380 ppm; and xylene at 1, 870 ppm) . <br /> IGeoAudit submitted a soli remediation plan/soil boring site <br /> assessment work plan to the SJ PHS/EHD on 21 August 1992 . GeoAudit <br /> proposed to drill approximately five soil borings to a depth of 30 <br /> feet, the presumed maximum depth of soil contamination. <br /> PROCEDURES <br /> Drilling was performed on 9 October 1992 . Soil boring B1 was <br /> located in the center of the former tank cavity, in order to <br /> determine the probable maximum vertical extent of contamination. <br /> The CME-75 and two man drill crew were supplied by West Hazmat <br /> Drilling Corporation. <br /> Discrete soil samples were collected ahead of the drill bit using <br /> a split-tube sampler loaded with three pre-cleaned 2 . 5 by 6 inch <br /> brass tubes. The samples were obtained at five-foot intervals, <br /> using a 140 pound hammer. To avoid cross contamination, the <br /> sampling equipment was washed in a tri-sodium phosphate (TSP) <br /> solution and rinsed twice with water prior to each sampling run. <br />