SU0003895 SSNL - Laserfiche WebLink

Home Browse Search

September 9, 2005 NOA Project Number. E05112A LAssociate's opinion that near surface aquifers are more likely to have elevated concentrations of Nitrate and DBCP than the deeper aquifers. However, the contaminant concentration in one aquifer does not give any indication as to the concentrations of any other aquifer regardless of proximity. f 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 Lfertilizers,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 was close to "natural" conditions. Based on the work by Bryan,it is estimated that under"natural" Lconditions,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 Lconcentrations may be increasing (Hull, 1984). DBCP was not found in the 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 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 nitrate sample was collected in a sterile plastic container;the DBCP sample was collected in two �4 sterile glass vials. The samples were then transported on ice and remained under chain of custody tote LPrecision Enviro-Tech,Stockton. 1t �Otl ffi : 4.6 Chain of Custody t i The Chain of Custody document has been included in the appendix of this report 5.0 SOIL PROFILE AND GEOLOGIC INFORMATION LThe Site is depicted on the Preliminary Geologic Map of the San Francisco - San Jose Quadrangle, California (1991),is within a region of Quaternary Fan deposits. The unit is composed of gravel, sandy silt and clay (Plate 3). IL L 6 ..44L