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L <br /> L September 10, 2004 <br /> NOA Project Number: E040104A <br /> 4.2 Potential Ground Water Contamination Issues <br /> Identifying potential ground-water contamination sources was not part of the scope of work <br /> ` for the soil suitability study. Potential ground-water contamination can occur from a number <br /> of sources which often include leaky underground storage tanks, agricultural activities, dairies, <br /> septic systems, and storm water infiltration. Any past agricultural activities and the present <br /> +� use of septic systems in the area should be considered potential ground-water contamination <br /> sources. <br /> 4.3 Water Sample Location <br /> L One domestic and one agricultural well exist on the Site. No records of these wells were <br /> found during file review at EHD on September 1, 2004. <br /> ` Three water samples were collected from an outside faucet fed by the on-site domestic water <br /> well on August 25, 2004 by Ms. Abigail Racco of our office. The locations of the well and <br /> water sample are indicated in Plate 1. <br /> 4.4 Water Sample Constituents <br /> • The water sample was analyzed for nitrate and DBCP. Nitrate was found at 32.5 mg/L-NO31 <br /> below the maximum contaminant level (MCL) set by the US EPA of 45 mg/L-NO3. DBCP <br /> was not detected in the water sample. The analytical reports prepared by Precision Enviro- <br /> Tech can be found in the appendix of this report. <br /> b, The presence of nitrates is not uncommon in shallow ground water aquifers in San Joaquin <br /> County and other parts of the Central Valley. Nitrate in ground water occurs as a result of <br /> „ the application of fertilizers, livestock waste, and untreated septic tank waste. Nitrate is <br /> ►. mobile and often accumulates in the shallow ground water zones. <br /> In the early 1900s, natural levels of nitrate in ground water were measured in forty-three (43) <br /> wells throughout the Sacramento Valley by Bryan (1923). It was thought that ground water at <br /> that time was close to "natural' conditions. Based on the work by Bryan, it is estimated that <br /> under "natural' conditions, ground water concentration containing nitrate is no more then <br /> 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 <br /> those in which nitrate concentrations may be increasing (Hull, 1984). <br /> L <br /> 6 <br /> '0004 <br /> V <br />