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N%1.11 I."001 <br /> June 14,2005 <br /> TOA Project Number: E05066A <br /> 3.2 Potential Ground Water Contamination Issues <br /> A discussion of issues related to potential ground water contamination is included in Section 4.2 of <br /> the SSS. <br /> /3.3Current and Future On-Site Ground Water Uses <br /> 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. The existing well is to be removed and a new well will be <br /> installed on the property. <br /> 4.0 SOURCES AND IMPACT OF NITRATE TO GROUND WATER <br /> y 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 9.83 mg/L-NO3. <br /> Y 4.2 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 /> �- 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 precipitation was obtained from the Western Regional Climate Center. The data for the <br /> �- Lodi Station (#045032) is available from July 1948 to September 2004. <br /> Average potential evapotranspiration was obtained from the California Irrigation Management <br /> `. Information System (CIMIS) Zone 12. <br /> Based on this method, the average deep percolation of rain for the Lodi area is estimated to b k5.7�6 <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 system for the residence. <br /> 3 <br />