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• <br /> WORK PLAN FOR THE INSTALLATION <br /> GROUNDWATER MONITORING WELLS <br /> 1649 East Channel Street <br /> Stockton, California <br /> INTRODUCTION <br /> In accordance with a request from Mr. Ed Gotelli of Mid-Cal <br /> Leasing, Geological Audit Services, Inc. (GeoAudit) has prepared <br /> this work plan to install three (3) groundwater monitoring wells at <br /> 1649 East Channel Street, Stockton, California (the site) . <br /> SITE DESCRIPTION <br /> The 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 is currently estimated at 65 - 75 feet below <br />. surface grade (San Joaquin County Department of Public Works, Flood <br /> Control Section, 1990) . <br /> PREVIOUS WORK <br /> TANK REMOVAL <br /> One 8 , 000 gallon diesel tank and one 10, 000 gallon diesel tank were <br /> removed from the site on 7 October 1988 . Soil contamination was <br /> encountered during the tank removal. The contaminated soil was <br /> excavated from the farmer tank cavity. The excavated soil was <br /> characterized and disposed of at a properly licensed landfill <br /> facility. <br /> On 12 July 1992 , a 1, 000 gallon gasoline tank was removed from the <br /> site. According to a letter from the San Joaquin County Public <br /> Health Services - Environmental Health Department (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 /> SOIL BORING INSTALLATION <br /> On 9 October 1992 , a soil boring was installed in the center of the <br />• tank cavity (B1; see Figure 2) . This boring was advanced to a depth <br /> of 60 feet. Samples were collected at five foot intervals and <br /> analyzed for total petroleum hydrocarbons (TPH as gasoline) and <br /> volatile aromatics (BTE&X) . <br />