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L u `/ LNovember 3,2004 NCA Project Number: E040119A 4.4 Water Sample Constituents y The water sample was analyzed for nitrate and DBCP. Nitrate was found at Non Detectable (ND) Levels at location DRS-1 and 6.9 mg/L-NO3 at location DRS-2 which is below the maximum contaminant level (MCL) set by the US EPA of 45 mg/L-NO3. DBCP was ND in both ground .�f� water samples. The analytical reports prepared by Precision Enviro-Tech can be found in the appendix of this report. L The 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. LIn 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 lr 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 L mg/L-N). Areas having 24.75 mg/I NO3 (5.5 mg/L-N) or more are those in which nitrate concentrations may be increasing (Hull, 1984). 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 L 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 water sample was obtained at the well head at both locations (Plate 5). The samples were Lcollected in a clean plastic container, then decanted into clean,glass vials. The samples were then (�.5) transported on ice and remanded under chain of custody to Precision Enviro-Tech,Stockton. David Welch of NCA collected the water samples. L 4.6 Chain of Custody LThe Chain of Custody document has been included in the appendix of this report. 64 G� L 5.0 SOIL PROFILE AND GEOLOGIC INFORMATION LThe Site is depicted on the USGS Geologic Map of the Sacramento-San Joaquin Delta, California, [` 1982.The map show the Site as Holocene peat and mud as part of tidal wetlands and waterways 5 '404 L