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January 4,2006 <br /> NOA Project Number: E05166B <br /> ` In 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 close to "natural" conditions. Based on the work by Bryan,it is estimated that under"natural' <br /> conditions,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/L-N) or more are those in which nitrate <br /> concentrations may be increasing (Hull, 1984). <br /> DBCP was detected in the water sample. DBCP is a nematocide and soil fumigant for vegetables <br /> and grapes. It is thought to cause health problems consisting of kidney damage,liver damage,and <br /> cancer. The use of DBCP was discontinued in 1979. The Environmental Protection Agency (EPA) <br /> set the maximum contaminant limit (MCL) at 0.2 parts per billion (ppb) because the EPA believes <br /> that given present technology and resources, this is the lowest level to which water systems can <br /> ` reasonably be required to remove this contaminant should it occur in drinking water. <br /> 4.5 Well Water Sample Collection, Handling, and Transportation <br /> <. %f The samples were collected in a sterile plastic container and two sterile glass vials. The samples were <br /> then transported on ice and remained under chain of custody to Precision Enviro-Tech,Stockton. <br /> 4.6 Chain of Custody <br /> The Chain of Custody document has been included in the appendix of this report. <br /> 5.0 SOIL PROFILE AND GEOLOGIC INFORMATION <br /> The Site is depicted on the USGS Preliminary Geologic Map of the Bellota Quadrangle as within the <br /> Quaternary Riverbank Formation. Quaternary Riverbank Formation (upper and middle members) <br /> ~ these units are arkosic alluvium forming Mokelumne River terraces and alluvial fan; chiefly sand; <br /> probably glacial outwash lower fans;abundant volcanic detritus (Plate 7). <br /> r The surface and near surface soils located at the Site are reported by the San Joaquin County Soil Survey <br /> to be composed of San Joaquin loam, thick surface,0-2% slopes (Plate 8) (USDA, 1992). Table 4 <br /> presents some selected properties of these soils: <br /> 6 <br />