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REPORT OF <br /> CONTAMINANT FATE AND TRANSPORT MODELING <br /> for <br /> Stockton Police Facility <br /> 22 East Market Street <br /> Stockton, California <br /> 1.0 INTRODUCTION AND PURPOSE <br /> h <br /> Smith Environmental Technologies Corporation has prepared this report on behalf of the;City of <br /> Stockton Public Works Department far,lsubmittal to and San Joaquin County Public Health Services <br /> ' Environmental Health Division (PHS/EHD) and the California Regional Water Quality Control Board <br /> (RWQCB). The purpose of the report°is to present the results of contaminant fate and transport <br /> modeling performed at the City of Siockton Police Facility in Stockton, California (Figure 1). <br /> Hydrocarbon impacted soil has been detected beneath the site during previous site investigations and a <br /> mathematical model was used to determine the fate and transport of impacted soil. <br /> J 2.0 HYDROGEOLOGIC SETTING <br /> The subject site is located in Stockton, California(Figure 1) situated on level terrain underlain by flood <br /> basin deposits of Pleistocene and Holocene age. These sediments are composed of clay, silt, and some <br /> sand. In the San Joaquin Valley, the Flood Basin Deposits (Holocene) have been estimated to be as <br /> much as 100 feet thick (USGS, 1985). ;;The USDA Soil Conservation Service identifies these'soils as <br /> "Jacktone Clay" (USDA, 1992)with soil organic matter content of 2 to 5 percent (1.16 to 2.9 percent <br /> organic carton). Because of their fine='grained nature, these deposits in general do not yield much <br /> water to wells and impede the vertical 'movement of water. The majority of groundwater used for <br /> irrigation and drinking water supplies is'extracted from more permeable water bearing zones beneath <br /> the flood basin deposits. <br /> } Based on data from on-site borings, the.soils beneath the subject site are comprised of clay and silt <br /> + from the surface to approximately 28 feet below surface grade, and silt and silty sand from 28 to 55 <br /> feet below grade, the total depth explored. A zone of fat clay (CH) exists from approximatelyE7 to 10 <br /> feet below grade which apparently significantly limits the potential for vertical migration of <br /> contaminants. <br /> r <br /> w\9436fte w Uses iLdoc 1 <br /> f Y� <br />