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\./ ..' <br /> LOctober 5,2005 <br /> NOA Project Number: E05129A <br /> L <br /> The presence of nitrates is not uncommon in shallow ground water aquifers in San Joaquin County <br /> and other parts of the Central Valley. Nitrate in ground water occurs as a result of the application <br /> of fertilizers,livestock waste,and untreated septic tank waste. Nitrate is mobile and often <br /> accumulates in the shallow ground water zones. <br /> I <br /> V <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 /> Lwas 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 not found in the sample. DBCP is a nematocide and soil fumigant for vegetables and <br /> 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 /> L <br /> 4.5 Well Water Sample Collection, Handling, and Transportation <br /> L <br /> The nitrate sample was collected in a sterile plastic container;the DBCP sample was collected in two <br /> L sterile glass vials. The samples were then transported on ice and remained under chain of custody to <br /> Precision Enviro-Tech in Stockton. <br /> L4.6 Chain of Custody <br /> The Chain of Custody document has been included in the appendix of this report. <br /> lr <br /> 5.0 SOIL PROFILE AND GEOLOGIC INFORMATION <br /> The Site is depicted on the Preliminary Geologic Map of Cenozoic Deposits of the Tracy <br /> Quadrangle, California (1981), as within a region of Quaternary Alluvium. The unit is one of <br /> poorly sorted gravel, sand silt and clay (Plate 3). <br /> i 7 <br /> --44 <br /> L <br />