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February 3, 2005 NOA Project Number: E040116A drilling of the percolation test holes to a depth of 3.0 feet on December 13, 2004 and January 17, 2005. 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. A Surface and Subsurface-Contamination Report addressed this issue (NOA, 2003). Please refer to this report for descriptions. Potential ground-water contamination can occur from a number of sources which often include leaky underground storage tanks;agricultural activities, dairies, septic systems, and storm water infiltration. Any past agricultural activities and the present use of septic systems in the area should be considered potential ground=water contamination sources. 4.3 Water Sample Location 4 1 � One permit, dated October 14, 1980,was found for the subject property address of 23544 Banta Road. This permit was for the replacement of a pipe and shorted wire for the domestic/private well.The permit does not indicate the depth or screening of the well. A water sample was taken from the pipe manifold near the well head from the well near the house Fi on December 14, 2004 (Plateal). 4.4 Water Sample Constituents The water Y e was ana sample zed for nitrate and DBCP. Nitrate was not detected in the water sample. DBCP was detected in the water sample at.0823 µg/L,below the EPA MCL- of 0.2 µg/L. The Fianalytical reports prepared by Precision Enviro-Tech can be found 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 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 having 24.75 mg/L-NO3 (5.5 mg/L-N) or more are those in which nitrate concentrations may be increasing (Hull, 1984). �� 5