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L November 8, 2004 NOA Project Number: E0401 10A L �.3 Potential Ground Water Contamination Issues L Identifying potential ground-water contamination sources was not part of the scope of work for the soil suitability study. Potential ground-water contamination can occur from a number of sources which often include leaky underground storage tanks, agricultural activities, dairies, septic systems, L and stone water infiltration. Any past agricultural activities and the present use of septic systems in the area should be considered potential ground-water contamination sources. Li/4.4 Water Sample Location Three water samples were collected from an irrigation pipe fed by the on-site irrigation water well L on October 1, 2004 by Ms. Abigail Racco of our office. The locations of the well and water sample are indicated in Plate 1. L ,4.5 Water Sample Constituents The water sample was analyzed for nitrate and DBCP. Nitrate was found at 6.0 mg/L-NO3,below [ the maximum contaminant level (MCL) set by the US EPA of 45 mg/L-NO3. DBCP was not Ldetected in the water sample. The analytical reports prepared by Precision Enviro-Tech can be found in the appendix of this report. 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. L 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 groundwater at that time was dose to "natural' conditions. Based on the work by Bryan,it is estimated that under"natural' L 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-NO, (5.5 mg/L-N) or more are those in which nitrate concentrations may be increasing (Hull, 1984). LDBCP 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 Lthis contaminant should it occur in drinking water. L L 5 '004 L