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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 /> Smith Environmental Technologies Corporation has prepared this report on behalf of the City of <br /> Stockton Public Works Department for submittal to and San Joaquin County Public Health Services <br /> Environmental Health Division (PHS/EHD) and the Calyforma 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 Stockton Pohce 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 /> 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, 1986) 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 carbon) 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 /> 1 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 approximately 7 to 10 <br /> feet below grade which apparently significantly lituts the potential for vertical migration of <br /> --- contaminants --- -_ -- - - - - ---- <br /> w 19436fteportskesoJ doc 1 <br /> SMTH <br /> i <br />