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r February 6, 2006 <br /> NOA Project Number. E05173A <br /> Page 5 <br /> ` 4.0 GROUND WATER INFORMATION <br /> 4.1 Ground Water Depth and Gradient <br /> The San Joaquin County Flood Control and Water Conservation District (1998 and 1999) ground <br /> water depth and elevation maps were reviewed to determine the ground water levels near the Site. <br /> The Fall 1998 and Spring 1999 maps are the most current maps available from the County. <br /> ` Examination of these maps indicates that no water level dda ble for the Tracy/Banta area, <br /> which includes the Site, and no definite comments as to epth or dient flow direction can be <br /> made.The depth to water in this area is typically abtt <br /> 10fee The depth to ground water <br /> r <br /> below the site is not known. <br /> 4.2 Potential Ground Water Contamination Issues <br /> Identifying potential ground-water contamination sources was not part of the scope of work for the <br /> soil suitability study. <br /> ` Potential ground-water contamination can occur from a number of sources which often include leaky <br /> underground storage tanks,agricultural activities,dairies, septic systems,and storm water infiltration. <br /> Any past agricultural activities and the present use of septic systems in the area should be considered <br /> ` potential ground-water contamination sources. Please see section 4.3 for additional water quality <br /> details. <br /> ` 4.3 Water Sample Location <br /> LTbree water we . exist on the subject property. A nitrate and DBCP well water s was collected <br /> ntrlreestic water eE head located at 33510 S. Koster Road,nroyose arcel 4. <br /> The water sample was analyzed for nitrate d DBCP. Nitrate was found a 19.9 NO3,w4U— <br /> �` below the m ' ntaminant le (MCLet by the US EPA of 45 mg/L- 03. DBCP was not <br /> etected in the water sample. The c reports prepared by Precision Enviro-Tech can be found <br /> In e appendix of this report. <br /> The presence of nitrates is not uncommon in shallow ground water aquifers in San Joaquin County <br /> and other parts of the Central Valley. Nitrate in ground water occurs as a result of the application of <br /> fertilizers,livestock waste,and untreated septic tank waste. Nitrate is mobile and often accumulates <br /> in the shallow ground water zones. <br /> In the early 1900s,natural levels of nitrate in ground water were measured in forty- ee (43) tells <br /> throughout the Sacramento Valley by Bryan (1923). It was thought that ground water ne <br /> was close to "natural' conditions. Based on the work by Bryan,it is estimated that under"natural' <br /> 5 <br />