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November 19,2004 NOA Project Number: E04107A 4.3 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 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. Mr. Mike Huggins, supervising environmental health specialist R.E.H.S. of EHD,indicated that this area c onl has high levels of nitrate in the shallow aquifer. The EHD.believes there is nitrate contamination of ground water e ow the site, an in the area,is a potential problem. 4.4 Water Sample Location As per the request of Mr.-Mike Huggins, the ground water sample was collected from the ground txT�rina excavated on the site October 28, 2004. Ms. Nancy Rosulante ek an r. Damer or our office excavated the boring and collected the water sample. The location of thejround water bo ' ercolatio P-. ch is cated on Plate 2. 4.5 Water Sample Constituents The water sample was analyzed for nitratF and 1�BC_P. Nitrate was found at 1.1 m /L-NO ell 4/0-` /11`!/Z.- below 11` f, below the maximum contaminant level (MCL) set by the US EPA of 45 mg/L-NO3. DBCP was A� not detected in the water sample. The analytical reports, and a chain of custody 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. As noted earlier, Mr. Mike Huggins has indicated this area has high nitrate levels in the well water. 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 nitrate concentration is no more then about 13.5 mg/L-NO3 (3 mg/L-N). F! 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). ! 1 5 F! Fj