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4.4 Preliminary Site Conceptual Model <br /> The Site Conceptual Model (SCM) is a written and/or graphical representation of the unauthorized release <br /> scenario, site characteristics (geology, hydrogeology, etc ) and the likely distribution of constituents of <br /> concern <br /> at the site The SCM links potential sources to potential receptors through transport of chemicals in air, <br /> soil, surface and groundwaters It also provides a technical framework for the entire project and a <br /> communications tool for regulatory agencies, responsible parties, and other parties involved in the <br /> investigation and ultimate cleanup of the site <br /> The overall goals of the Site Conceptual Model are listed below <br /> 1 Identify how the distribution of chemical is changing in space and time, <br /> 2 Identify potential current and future receptors, <br /> 3 Identify environmental issues that need to be addressed <br /> The Parmar Texaco Preliminary SCM Includes the following bask site information parameters <br /> 1 Site Description Parmer Texaco, 521 North Cherokee Lane, Lodi, ,California <br /> 2 Land Use Former Service Station Equipment Supplier Current land use is automotive tire <br /> service shop <br /> 3 Water Use City of Lodi supplied water and City of Lodi sewer and storm drain service <br /> provided to property No release of to ground surface of any liquids Several water supply <br /> wells for both individual properties and municipal water supply source within distance of <br /> 2,000 feet <br /> 4 Chronology of Events five USTs were probably in service from about 1965-1983 UST not <br /> used after 1983 Only contaminant is gasoline as petroleum hydrocarbon Benzene, 1,2- <br /> DCA, and MTBE occur at concentrations of concern MTBE concentrations on site exceed <br /> primary MCL of 13 µg11 1,2-DCA concentrations on site exceed primary MCL of 5 µg/1 <br /> Benzene concentrations on site exceed the primary MCL of 5gg/1 <br /> 5 Site Stratigraphy and Hydrogeoloay Stratigraphy is at least upper 60 foot thickness of <br /> interbedded medium to fine grained sands and silt or clayey silt lenses that are several feet <br /> thick These sediments contain the petroleum hydrocarbon release Hydrogeology is <br /> summarized by flow direction that is southwesterly to southerly at a low-gradient Local flow <br /> Pae 23 <br /> Mam1D IEnwonmentallPanntQTexacolReportslSAR1203 wpd g <br />