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July 11, 2007 <br /> NOA Project Number: E07094A <br /> In the early 1900s,natural levels of nitrate in ground water were measured in forty-three (43) wells <br /> - 1 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/1,N) or more are those in which nitrate <br /> concentrations may be increasing (Hull, 1984). <br /> ' } DBCP was not found 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 /> FiThe sample for nitrate was collected in a sterile plastic container, the sample for DBCP was <br /> collected in two sterile glass vials. The samples were then transported on ice and remained under <br /> F1chain of custody to FGL Environmental, Stockton. <br /> 4.6 Chain of Custody <br /> E 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 Geologic Map of the San Francisco-San Jose�uadrangle (1991) as within <br /> the Quaternary Modesto Formation (Plate 7). These map units represent arkosic alluvium forming <br /> Mokelumne River terraces, channel ridges and alluvial fans. <br /> The surface and near surface soils located at site are reported by the San Joaquin County Soil Suruey to <br /> be composed of Jack Tone clay and Jack Tone Urban Land Complex, both 0-2 % slopes (Plate 7) <br /> F (USDA, 1992). Table 2 presents some selected properties of these soils: <br /> t. <br /> F1 6 <br />