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L L July 30,2005 NOA Project Number: E05089A 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' f` conditions,ground water concentration containing 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 may be increasing (Hull, 1984). Y DBCP was not detected in the water sample. The Environmental Protection Agency (EPA) set the maximum contaminant limit (MCL) for DBCP at 0.2 parts per billion (ppb) because the EPA Lbelieves 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. 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. 4.5 Well Water Sample Collection, Handling, and Transportation The samples were collected in a sterile plastic container, then decanted into sterile,glass vials. The samples were then transported on ice and remanded under chain of custody to Precision Enviro- Tech, Stockton. 4.6 Chain of Custody i The Chain of Custody document has been included in the appendix of this report. L 5.0 SOIL PROFILE AND GEOLOGIC INFORMATION LThe Site is depicted in the US Department of the Interior Geological Survey Open File Report 80- 535, as Holocene Alluvium. This map unit is described as, "Channel,levee, and floodplain deposits; chiefly silt and clay with fine sand along principle drainage ways." The surface and near surface soils located at the Site are reported by the San Joaquin County Soil Survey to be composed of Capay clay,wet, 0 to 2 percent and 2-5 percent slopes.The surface is also Lcomposed of Stomar clay,0-2 percent slopes (USDA, 1992;Plate 4). Table 3 presents some selected properties of this soil type: L L L 6 L '404 L