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November 19, 2004 <br /> NOA Project Number: E040107A <br /> 2.3 Current and Future On-Site Ground Water Uses <br /> A description of the existing wells on the Site is included"in Section 4.2 of the SSS. Ground water is <br /> rlused for domestic purposes and is developed on the northern parcel. <br /> F1 3.0 SOURCES AND IMPACT OF NITRATE TO GROUND WATER <br /> 3.1 Current Off-Site Sources of Nitrate } <br /> F1We recognize that septic systems, agriculture, and dairies in the area may be the most significant <br /> sources of nitrate. Septic tank use in the vicinity is discussed in Section 3.4 of the SSS and is 'Y �.. <br /> estimated to 78 systems per s ware mile. The ground water sample, discussed in Sections 4.4 <br /> F1through 4.7 of the SSS,was found to have a nitrate concentration of 1 Ll mg/L-NO- This y <br /> concentration of this sample suggests that the ground water aquifer is may not bexe periencing i'gy,F1 <br /> nitrate leaching from sources in the area. <br /> 3.2 Contribution of Rainfall <br /> FiAn 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 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 4 for the <br /> data and calculation. <br /> P <br /> Averagepotential evapotranspiration was obtained from the California Irrigation Management <br /> Information System (CIMIS). Tracy is located within evapotranspiration zone number 12. The <br /> average rainfall for the Tracy Pump Station, obtained from the Western Regional Climate Center, <br /> F was 12.14 inches (average for February 1955 to June 2004). <br /> Based on this method, the average deep percolation of rain for th� e Tracy area is estimated to be 0.45 <br /> inches. The nitrate concentration of rain fall was estimated to be 1 mg/L-N (Hantzsche and <br /> Fj Finnemore, 1992). <br /> 3.3 Current On-Site Sources of Nitrate <br /> There are no operating current on-site sources of nitrate. <br /> 3.3.1 Existing Septic System <br /> There are no septic systems on either parcel. <br /> 3 <br /> Fill <br />