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Farmington Murphy Prope, <br /> Our PrOject Number: E072�3A Page 3 <br /> December 24,2007 <br /> 2.2 Potential Ground Water Contamination Issues <br /> A discussion of issues related to potential ground water contamination is included in Section 4,2 <br /> of the SSS completed by Dillon & Murphy. <br /> 2.3 Current and Future On-Site Ground Water Uses <br /> A ground water wells exists on the site, as noted in Section 4.3 of the $SS by Dillon & Murphy. <br /> We understand ground water will be developed and used on the site in the future. <br /> 3.0 SOURCES AND IMPACT OF NITRATE TO GROUND WATER <br /> 3.1 Current Off-Site Sources of Nitrate <br /> Septic systems, agriculture, and dairies in the area may be the most significant sources of <br /> nitrate in ground water. Septic tank use in the vicinity is discussed in Section 3.4 of the SSS by <br /> Dillon & Murphy. <br /> 3.2 Contribution of Rainfall <br /> An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. <br /> The estimate of deep percolation of rain is based on the average monthly precipitation of rain <br /> fall and evapotranspiration for South Stockton, California. The estimate first determines <br /> whether the average monthly precipitation exceeds average monthly potential <br /> evapotranspiration. If so, then the difference is potential deep percolation. This method does <br /> not consider runoff. See Plate 1 for the 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. <br /> Average rainfall was obtained from the Western Regional Climate Center (Station 048558) for <br /> both the north and south Stockton areas. <br /> Table 1. <br /> Estimate of_peep Percolation of Rain for the Site <br /> Location Deep Percolation of Rain <br /> South Stockton Plate 1a 3.3 inches <br /> North Stockton Plate 1b 4.7 inches <br /> Average: 4.0 inches <br /> Based on this method, the average deep percolation for both the rain for the north and south <br /> Stockton area is estimated to be 4.0 inches. The nitrate concentration of rain fall was <br /> estimated to be 1 mg/L-N (Hantzsche and Finnemore, 1992). <br /> 3.3 Current On-Site Sources of Nitrate <br /> There are no current on-site sources of nitrate except for natural processes. <br /> '.44 <br /> 902 Industrial Way-Lodi.CA 95240•209.367.3701 -Fax 209,369.4228 (72007 Neil 0.Anderson&Assocvmv,Me <br />