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7 September 9, 2005 - NOA.Project Number: E05110A The presence of-nitrates is not uncommonin-shallow ground water aquifers in San Joaquin County and other parts of the Central Valley. Nitrate in groundwater 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 mg/L-N). Areas having 24.75 mg/L-NO3 (5.5 mg/L-N) or more are those in which nitrate concentrations rimy be increasing (Hull, 1984). DBCP was not found in the saiinple. 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 systems can reasonably be required to remove this contaminant should it occur in diinking water. 4.5 Well Water Sample Collection, Handling, and Transportation The sample for nitrate was collected in a sterile plastic container,-the sample for DBCP was collected in two sterile glass vials:-The samples were_then transported on ice and remained under- chain of custody to Precision Enviro-Tech, Stockton. 4.6 Chain of Custody_ The Chain-of Custody document .-has been-included in.the.appendix-of this report... 5.0 50IL'PROFILE ANDVGEOLOGIC INFORMATION The Site is depicted on the USGS Pteliminary Geologic Map of San Francisco - San Jose F1 Quadrangle as within the Quaternary Riverbank Formation. Quaternaty Riverbank Formation is composed of: weathered,reddish gravel, sand, and silt forming clearly recognizable alluvial terraces and fans (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 Madera sandy.loam and Madera-Alamo complex;leveled;both 0-2% slopes (Plate 8) (USDA',.1992).'Table 2 presents some selected properties of these soils. Fi _..