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i February 15,-2006 k NOA Project Number: E06006A 4.2 Potential Ground Water Contamination Issues 1 Identifying potential ground water contamination sources was not part of the scope of work for the F1soil suitability study. Potential ground water contamination can occur from a number of sources which often include Fi 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 No well permits were found €or the subject property address of 9103 South Airport Way during file 4 review at EHD on January 31, 2006. -However, one domestic well and one agricultural well are located on the Site. The locations of the wells are indicated on PlateJ. One water sample was taken on January 31,-2006 from the closest spigot to the domestic well on the northeast side of the residence. The location of the sample is depicted ori Plate 1. 4.4 Water Sample Constituents The water sample was analyzed for nitrate and DBCP. Nitrate was found at 114;mg/L-N031 well F1 above the maximum contaminant level{MCL) set by the US EPA'of 45 mg/L-NO3. DBCP was not detected in the water sample. The analytical reports prepared by.FGL Environmental can be found in the appendix of this report. The presence of nitrates is riot 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 y was close to "natural" conditions. Based on the work by Bryan, it is estimated that under"natural" conditions,ground water concentrationcontaining 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 {"4 concentrations may be increasing (Hull, 1984). a R 5