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um <br /> vow January 4,2006 <br /> NOA Project Number: E05166B <br /> ilm j/3.3 Current and Future On-Site Ground Water Uses <br /> 3 A description of the existing wells on the Site is included in Section 4.3 of the SSS. Ground water is <br /> ` currently used for residential purposes. Ground water will be developed and used on the rest of the <br /> parte s'mthe future. <br /> 4.0 SOURCES AND IMPACT OF NITRATE TO GROUND WATER <br /> 4.1 Current Off-Site Sources of Nitrate <br /> Septic systems,agriculture, and dairies in the area may be the most significant sources of nitrate. <br /> `� Septic tank use in the vicinity is discussed in Section 3.4 was found to be moderate. The ground <br /> water sample, discussed in Sections 4.3 through 4.6 of the SSS,was found to have a nitrate <br /> concentration of 1.74 m /L-NO3. This concentration indicates that the ground water aquifer is <br /> ` ely not experiencing nitrate leaching from various sources in the area over the long term. <br /> r 4.2 Contribution of Rainfall <br /> y, a <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 rainfall and <br /> ` evapotranspiration for Lodi, California. The estimate first determines whether the average monthly <br /> precipitation exceeds average monthly potential evapotranspiration. If so, then the difference is <br /> potential deep percolation. This method does not consider runoff. See Plate 9 for the data and <br /> calculation. <br /> Average potential evapotranspiration and average rainfall data was obtained from the California <br /> ` Irrigation Management Information System (CIMIS). The data from January 1988 to December <br /> 2004 was used for the calculation. <br /> ` Based on this method, the average deep percolation of rain for the Lodi area is estimated <br /> inches. The nitrate concentration of rain fall was estimated to be 1 mg/L-N (Hantzsche and <br /> Finnemore, 1992). <br /> ,/4.3 Current On-Site Sources of Nitrate <br /> Current on-site sources of nitrate include the current septic systems for the residences. <br /> 3 <br />