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September 30, 2007 NOA Project Number: E07141A It is Neil O. Anderson and Associate's opinion that, in general, near surface aquifers are more likely to have elevated concentrations of Nitrate and DBCP than the deeper aquifers. However, the contaminant concentration of one aquifer cannot give any indication as to the concentrations of any,�-'— other aquifer regardless of proximity. The presence of nitrates is not uncommon in shallow groundwater aquifers in San Joaquin County and other parts of the Central Valley. Nitrate in ground water occurs as a result of the application of fertilizers,livestock waste, and untreated septic tank waste. Nitrate is mobile and often accumulates in the shallow ground water zones. In the early 1900s, natural levels of nitrate in ground water were measured in forty-three wells tYree (43) throughout the Sacramento Valley by Bryan (1923). It was thought that ground water at that time was close to "natural" conditions. Based on the work by Bryan,it is estimated that under "natural" conditions, the ground water concentration of nitrate is no more then about 13.5 mg/L-NO3 (3 mg/L-N). Areas having 24.75 mg/L-NO3 (5.5 mg/L-N) or more are those in which nitrate concentrations ay be increasing (Hull, 1984). D� P was not detected ' the water sample. DBCP is a nematocide and soil fumigant for veg�t$bles-and-grapes. It is thought to cause health problems consisting of kidney damage, liver damage, and cancer. The use of DBCP was discontinued in 1979. The Environmental Protection Agency (EPA) set the maximum contaminant limit (MCL) at 0.2 parts per billion (ppb) because the EPA believes that given present technology and resources, this is the lowest level to which water systems can reasonably be required to remove this contaminant should it occur in drinking water. 4.5 Well Water Sample Collection, Handling, and Transportation The samples were collected in a sterile plastic container and two sterile glass vials. The samples were then transported on ice and remained under chain of custody to FGL Environmental, Stockton. \ 4.6 Chain of Custody The Chain of Custody document has been included in the appendix of this report. 5.0 SOIL PROFILE AND GEOLOGIC INFORMATION The site is de ori the Preliminary Geologic Map of the San Francisco - San Jose Cenozoic Quadra , as within region of Quaternary Fan deposits. The unit consists of gravel, sandy silt and,c y (Plate 3). The sur ace and near surface soils located at the site are reported by the San Joaquin County Soil Survey to be composed of the Capay clay,wet, 0-2% slopes (Plate 4) (USDA, 1992). Table 2 presents some selected properties of the soils: 5