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L LJuly 28,2006 NOA Project Number: E05167B LThe presence of nitrates is not uncommon in shallow ground water 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 (43) wells 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,ground water concentration containing nitrate is no more then about 13.5 mg/L-NO3 (3 6 mg/L-N). Areas having 24.75 mg/L-NO3 (5.5 mg/L-N) or more are those in which nitrate concentrations may be increasing (Hull, 1984). LDBCP was not detected in the water sample. DBCP is a nematocide and soil fumigant for vegetables 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 Lsystems can reasonably be required to remove this contaminant should it occur in drinking water. 4.5 Well Water Sample Collection,Handling, and Transportation The nitrate sample was collected in a sterile plastic container, the DBCP sample was collected in two sterile glass vials. The samples were then transported on ice and remained under chain of custody to LFGL Environmental in Stockton. 4.6 Chain of Custody The Chain of Custody document has been included in the appendix of this report. L 5.0 SOIL PROFILE AND GEOLOGIC INFORMATION L The Site is depicted on the California Geological Survey Geologic Maf�of Cenozoic Def osits of the San Francisco-San Jose Quadrangle (199 1) as within the CDMG Map 5A. The Modesto Formation consists of Arkosic alluvium forming Mokelumne River terraces and alluvial fan; chiefly sand with minor j gravel and silt;probably glacial outwash (Plate 7). The surface and near surface soils located at the Site are reported by the San Joaquin County Soil Survey to be composed of Galt clay, Hollenbeck silty clay,Jacktone clay and Stockton clay, all 0-2% slopes (Plate 8) (USDA, 1992). Table 3 presents some selected properties of these soils: i L 5 L