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Soil Suitability I Nitrate Loading Study <br /> Proposed Global Carrier Inc. ■ Manteca, California 1rerracon <br /> August 8, 2018 s Terracon Project No. NA187034 <br /> 2.2 Groundwater Analysis <br /> 2.2.1 Regional Groundwater <br /> A discussion of regional groundwater, including depth to groundwater and flow gradient is <br /> included in Section 1.4.1. No significant seasonal trends were evident from the sources <br /> consulted. <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 /> One domestic groundwater well is located south of the existing garage and is anticipated to <br /> provide potable water for the future site development. <br /> 2.3 Sources and Impact of Nitrate to Groundwater <br /> 2.3.1 Current Off-Site Sources of Nitrate <br /> Agriculture land use, residential septic systems, and industrial septic systems in the area may be <br /> contributing sources of nitrate to groundwater. A groundwater study titled Addressing Nitrate In <br /> California's Drinking Water Technical Report 2 Nitrogen Sources and Loading to Groundwater <br /> dated 2012 prepared by the University of California Davis for the Tulare Lake Basin and Salinas <br /> Valley, indicated crop land contributed 96% of the human-generated nitrate sources to <br /> groundwater. The study indicated other minor contributors to nitrate in groundwater included <br /> waste water treatment plants, septic systems, corrals, lagoons and urban runoff. Based on the <br /> groundwater study, agricultural land use on the site and vicinity is anticipated to be the highest <br /> contributor to nitrates in groundwater. <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 Manteca, 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 G for the data and calculation. <br /> Responsive■ Resourceful ■ Reliable 14 <br />