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L <br /> LFebruary 3,2005 <br /> NOA Project Number: E040143A <br /> LIn the early 1900s,natural levels of nitrate in ground water were measured in forty-three (43) wells <br /> throughout the Sacramento Valley by Bryan (1923). It was thought that ground water at that time <br /> was dose to"natural" conditions. Based on the work by Bryan,it is estimated that under"natural" <br /> Lconditions,ground water concentration containing nitrate is no more then about 13.5 mg/L-NO3 (3 <br /> mg/L-N). Areas having 24.75 mg/L-NO3 (5.5 mg/1,N) or more are those in which nitrate <br /> concentrations may be increasing (Hull, 1984). <br /> LDBCP is a nematocide and soil fumigant for vegetables and grapes. It is thought to cause health <br /> L problems consisting of kidney damage,liver damage,and cancer. The use of DBCP was <br /> discontinued in 1979. The Environmental Protection Agency (EPA) set the maximum contaminant <br /> limit(MCL) at 0.2 parts per billion (ppb) because the EPA believes that given present technology <br /> L and resources, this is the lowest level to which water systems can reasonably be required to remove <br /> this contaminant should it occur in drinking water. <br /> 4.5 Well Water Sample Collection, Handling, and Transportation <br /> LThe samples were collected in a clean plastic container, then decanted into clean,glass vials. The <br /> samples were then transported on ice and remanded under chain of custody to Precision Enviro- <br /> Tech, Stockton. <br /> L 4.6 Chain of Custody <br /> The Chain of Custody document has been included in the appendix of this report. <br /> i <br /> 6' 5.0 SOIL PROFILE AND GEOLOGIC INFORMATION <br /> LThe Site is depicted on the Preliminary Geologic Map of the San Francisco- San Jose Cenozoic <br /> Deposits of the Tracy Quadrangle, California (1981), as within a region of Quaternary Fan Deposits <br /> and Quaternary Dos Palos Alluvium.The Fan Deposits are composed of gravel, sand silt and clay. <br /> kThe Dos Palos Alluvium is a unit of flood basin deposits: poorly sorted gravel, sand silt and day <br /> ` (Plate 7). <br /> L The surface and near surface soils located at the Site are reported by the San Joaquin County Soil Survey <br /> to be composed of Willows clay,partially drained, 0-2 percent slopes (Plate 8) (USDA, 1992). Table <br /> 3 presents some selected properties of the soil: <br /> L <br /> 1 <br /> L <br /> L 6 .*44 <br /> L <br />