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wr <br /> -F1 <br /> December 12,2006 <br /> NOA Project Number: E06094A <br /> f-• <br /> 2.0 GROUNDWATER ANALYSIS <br /> 3 <br /> 4 <br /> 2.1 Regional Ground Water <br /> According to San Joaquin County Flood Control and Water Conservation District maps of Spring <br /> 1999,groundter'iri the vicinity is estimated to be between five and ten feet below ground surface: <br /> 2.2 Current and Future On-Site Ground Water Uses <br /> The use of ground water for drinking water is planned for the proposed development. There are <br /> we on site associated with the residences on the property. <br /> currently two <br /> 3.0 SOURCES AND IMPACT OF NITRATE TO GROUND WATER <br /> -y 3.1 Current Off-Site Sources of Nitrate <br /> Septic systems,;agriculture, and dairies in the area may be the most significant sources of nitrate in <br /> the county. <br /> In an attempt to determine the septic system density for the vicinity of the Site, our office reviewed <br /> a recent aerial photograph of the subject property available from Google Earth. We counted the <br /> 7" building clusters within one square mile of the Site, and made the assumption that each building <br /> cluster has one;septic system. Using this method,we determined that there are a minimum of 200 <br /> septic system per square mile in the immediate vicinity of the Site. It is unclear whether the entire <br /> area utilizes septic systems for domestic waste water disposal. <br /> - ' The general use of the vicinity is residential. <br /> 3.2 Contribution of Rainfall <br /> An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. The <br /> i 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 /> g <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 1 for the <br /> . € data and calculation. <br /> .Average potential evapotranspiration was obtained from the California Irrigation Management <br /> i -Information Spstem-(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 /> (www.wrcc.dri.edu), and was found to be 15.98 inches per month for the years 1965 through 1977. <br /> i <br />