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` May 26,2005 NOA Project Number: E05004A the drilling of one of the percolation test holes to a depth of 25 feet on May 13,2004. The ground water level was found to be at 18 feet below the ground surface. 4.2 Potential Ground Water Contamination Issues Identifying potential ground-water contamination sources was not part of the scope of work for the Lsoil 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. L /4.3 Water Sample Location One well permit was found for the subject property address of 23250 North Sowles Road during file review at EHD on January 28, 2005. This permit, dated February 17, 1985,was for the installation of a new domestic well. A water sample was taken on April 25, 2005 from the pipe manifold near the domestic well head 7� Y Q near the house on the property by Mr Conor McGee of our office (Plate 1). U14_ 7 1 : /4.4 Water Sample Constituents ��ii The water sample was analyzed for nitrate and DBCP. Nitrate was found at<: 1.3 me/L-NOS,. below the maximum contaminant level (MCL) set by the US EPA of 45 mg/L-NO3. D -IMP-Wriis-not detected in the water same le. The analytical 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' f� 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). L L 5 "04 I �