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July 6,2007 <br /> NOA Project Number: E07096A <br /> 2.3 Current and Future On-Site Ground Water Uses �] <br /> The use of ground water for drinking water is planned for the proposed development. Zz <br /> 3.0 SOURCES AND IMPACT OF NITRATE TO GROUND WATER <br /> 3.1 Current Off-Site Sources of Nitrate <br /> F1 Septic systems, agriculture, and dairies in the area may be the most significant sources of nitrate in 01, <br /> the county. Septic tank use in the vicinity is discussed in the SSS report (Dillon&Murphy, 2007). <br /> F13.2 Contribution of Rainfall <br /> An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. The <br /> estimate of deep percolation of rain is based on the average monthly precipitation of rain fall and <br /> 0 evapotranspiration for Stockton, California. The estimate first determines whether the average <br /> monthly precipitation exceeds average monthly potential evapotranspiration. If so,then the <br /> difference is potential deep percolation. This method does not consider runoff. See Plate 1 for the <br /> data and calculation. <br /> Average potential evapotranspiration was obtained from the California Irrigation Management <br /> Information System (CIMIS). Stockton is located within evapotranspiration zone number 12. The <br /> average rain fall for the Stockton area was obtained from the Western Regional Climate Center <br /> P (www.wrcc.dri.edu), and was found to be 14.96 inches per month for the years 1965 through 1977. <br /> Based on this method,the average deep percolation of rain for the Stockton area is estimated to be <br /> 4.00 inches. The nitrate concentration of rain fall was estimated to be 1 mg/L-N (Hantzsche and <br /> F1 Finnemore, 1992). <br /> 3.3 Current On-Site Sources of Nitrate <br /> Current on-site sources of nitrate include any current septic systems on the property. No additionalFi <br /> sources of nitrates besides septic effluent,groundwater and rainfall are recognized. l 3 J <br /> 3.4 Future On-Site Sources of Nitrate <br /> 3.4.1 Quantity and Quality of Domestic Wastewater From Proposed Project <br /> The following discussion is for determining the long-term waste water flow generated from the <br /> p proposed residences or commercial usage for the nitrate loading analysis and should not be used for <br /> septic system design purposes. Typically,use estimates for the sizing of septic systems include a <br /> peak use factor,whereas the numbers discussed here are based on long-term averages. <br /> 4 <br /> Fj 4 . <br /> F1 <br />