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I February 24,2006 NOA Project Number: E05139B drilling of a percolation test hole to a depth of 25 feet on January 30,2006. 4.2 Potential Ground Water Contamination Issues 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 L which often include leaky underground storage tanks, agricultural activities, dairies, septic systems and storm water infiltration. Agricultural activities and the use of septic systems and dairies in the area should be considered potential ground-water contamination sources. L4.3 Water Sample Location L Both septic permits indicate that there is an existing well on the property near the rice dryer / structures. The water sample was taken from the spigot of the bathroom inside the office building. L4.4 Water Sample Constituents [ The water sample was analyzed for nitrate and DBCP. Nitrate was found'r 115.5 L- O3,which ` ) is below the maximum contaminant level (MCL) set by the US EPA of 4 mg/L- 03. DBCP was ^� V not detected in the water sample. The analytical reports prepared by Precision nviro-Tech can be Lfound in the appendix of this report. ` 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. In the early 1900s,natural levels of nitrate in ground water were measured in forty-three (43)wells 6 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 vi 24.75 mg/L-NO3 (5.5 mg/L-N) or more are those in which nitrate concentrations may be in reasing (Hull, 1984). L DBCP was not detected in a water sample. DBCP is a nematocide and soil fumigant for Vegetables and grapes. I s thought to cause health problems consisting of kidney damage,liver L darimgerand e 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 Lsystems can reasonably be required to remove this contaminant should it occur in drinking water. { (r 5 'oAL L