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Soil Suitability/Nitrate Loading Study Irerracon <br /> Proposed Commercial Truck Yard ■ Stockton, CA <br /> August 16, 2019 ■ Terracon Project No. NA197053 <br /> 2.2.3 Current and Future On-Site Ground Water Uses <br /> There are no groundwater wells on the site. A groundwater is proposed to be developed on the <br /> southern portion of the site prior to development. <br /> 2.3 Sources and Impact of Nitrate to Groundwater <br /> 2.3.1 Current Off-Site Sources of Nitrate <br /> Septic systems in the area may be the most significant sources of nitrate in groundwater. Septic <br /> tank use in the vicinity is discussed in Section 1.3.5. <br /> 2.3.2 Contribution of Rainfall <br /> An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. <br /> Average precipitation and potential evapotranspiration data was obtained from the California <br /> Irrigation Management Information System (CIMIS)from the Holt(248)and Manteca (070), CIMIS <br /> stations located nearest to the site. The estimate of deep percolation of rain is based on the <br /> average monthly precipitation of rain fall and evapotranspiration for San Joaquin County, <br /> California. The estimate first determines whether the average monthly precipitation exceeds <br /> average monthly potential evapotranspiration. If so, then the difference is potential deep <br /> percolation. This method does not consider runoff, although due to the relatively flat nature of the <br /> site runoff should be minimal. <br /> Table 9. <br /> Estimate of Deep Percolation of Rain <br /> Location Average Deep Percolation of Rain <br /> French Camp Area 1.77 inches per year <br /> Based on this method, the average deep percolation of rain for the French Camp Area is <br /> estimated to be 1.77 inches/year. <br /> The nitrate concentration of rainfall is estimated to be 1 mg/L-N (Hantzsche and Finnemore, <br /> 1992). <br /> 2.3.3 Current On-Site Sources of Nitrate <br /> The current on-site sources of nitrate include natural processes. <br /> 2.3.4 Future On-Site Sources of Nitrate <br /> Future on-site sources of nitrate include the proposed septic system and natural processes. <br /> Responsive■ Resourceful ■ Reliable 14 <br />