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Soil Suitability / Nitrate Loading Study Irerracon <br /> Thor Property n Stockton, CA <br /> July 19, 2018 r Terracon Project No. NA187029 <br /> 2.2.2 Potential Ground Water Contamination Issues <br /> A discussion of issues related to potential groundwater contamination is included in Section 1.4.2. <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 /> The estimate of deep percolation of rain is based on the average monthly precipitation of rain fall <br /> and evapotranspiration for Stockton, 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. Average potential evapotranspiration <br /> was obtained from the California Irrigation Management Information System (CIMIS). Refer to <br /> Appendix F for the data and calculation. <br /> Table 4. <br /> Estimate of Deep Percolation of Rain for the Site <br /> Location Deep Percolation of Rain <br /> Stockton 3.3 inches per year <br /> Based on this method, the average deep percolation of rain for the Stockton area is estimated to <br /> be 3.3 inches/year. The nitrate concentration of rainfall is estimated to be 1 mg/L-N (Hantzsche <br /> and Finnemore, 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 are discussed in section 1.3.7. <br /> Responsive ■ Resourceful ■ Reliable 13 <br />