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Soil Suitability/ Nitrate Loading Study Irerracon <br /> Ernst Property ■ Tracy, CA <br /> February 21, 2019 revised April 9, 2019 ■ Terracon Project No. NA197000 <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 <br /> Responsive■ Resourceful ■ Reliable 13 <br />