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L � � <br /> LNovember 27,2006 <br /> NOA Project Number: E06087A <br /> 2.3 Current and Future On-Site Ground Water Uses <br /> LThe use of ground water for drinking water is planned for the proposed development. There is <br /> currently one well on the Site. <br /> 3.0 SOURCES AND IMPACT OF NITRATE TO GROUND WATER <br /> 3.1 Current Off-Site Sources of Nitrate <br /> V <br /> Septic systems,agriculture, and dairies in the area may be the most significant sources of nitrate in <br /> the county. Septic tank use in the vicinity discussed in Section 3.4 was found to be very small. The <br /> onsite water well was tested for nitrate and DBCP. Neither constituent was detected. <br /> 3.2 Contribution of Rainfall <br /> r <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 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 9 for the <br /> data and calculation. t% <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 /> L (www.wrcc.dri.edu),and was found to be 15.98 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 /> 4.0 inches. The nitrate concentration of rain fall was estimated to be 1 mg/L-N (Hantzsche and <br /> Finnemore, 1992). <br /> 3.3 Current On-Site Sources of Nitrate <br /> L <br /> Current on-site sources of nitrate include the two current septic systems on the property. No <br /> additional sources of nitrates besides septic effluent,groundwater and rainfall are recognized. <br /> L <br /> i <br /> I� <br /> L <br /> 4 <br /> '-444 <br /> L <br />