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Soil Suitability / Nitrate Loading Study <br />Ernst Property ■Tracy,CA <br />February 21, 2019 revised April 9, 2019 ■ Terracon Project No.NA197000 <br />Responsive ■Resourceful ■Reliable 13 <br />2.2.3 Current and Future On-Site Ground Water Uses <br />There are reportedly no wells used to supply drinking water on the site, as noted in Section 1.4.3. <br />2.3 Sources and Impact of Nitrate to Groundwater <br />2.3.1 Current Off-Site Sources of Nitrate <br />Agriculture and septic systems in the area may be the most significant sources of nitrate in <br />groundwater. Septic tank use in the vicinity is discussed in Section 1.3.4. <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 Tracy (167) station. The estimate of <br />deep percolation of rain is based on the average monthly precipitation of rain fall and <br />evapotranspiration for San Joaquin County, California. The estimate first determines whether the <br />average monthly precipitation exceeds average monthly potential evapotranspiration. If so, then <br />the difference is potential deep percolation. This method does not consider runoff, although due <br />relatively flat nature of the site runoff should be minimal. <br />Table 4. <br />Estimate of Deep Percolation of Rain <br />Location Average Deep Percolation of Rain <br />San Joaquin County 1.01 inches per year <br />Based on this method, the average deep percolation of rain for San Joaquin County is estimated <br />to be 1.01 inches/year. The nitrate concentration of rainfall is estimated to be 1 mg/L-N <br />(Hantzsche and Finnemore, 1992). <br />2.3.3 Current On-Site Sources of Nitrate <br />The current on-site sources of nitrate include the existing septic system and natural processes. <br />2.3.4 Future On-Site Sources of Nitrate <br />Future on-site sources of nitrate are discussed in section 1.3.7. <br />2.3.4.1 Quantity and Quality of Wastewater from Project <br />The following discussion is for determining the long-term wastewater flow generated from the <br />proposed development for the nitrate loading analysis and should not be used for septic system