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Nitrate Loading Study Irerracon <br /> Arellano Property r-� Stockton, California <br /> April 26, 2019 Terracon Project No. NA187058 <br /> A groundwater study titled Addressing Nitrate In California's Drinking Water Technical Report 2 <br /> Nitrogen Sources and Loading to Groundwater dated 2012 prepared by the University of <br /> California Davis for the Tulare Lake Basin and Salinas Valley, indicated crop land contributed <br /> 96% of the human-generated nitrate sources to groundwater. The study indicated other minor <br /> contributors to nitrate in groundwater included waste water treatment plants, septic systems, <br /> corrals, lagoons and urban runoff. Based on the groundwater study, agricultural land use on the <br /> site and vicinity is anticipated to be the highest contributor to nitrates in groundwater. <br /> 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). Data from the Manteca (070)and Holt(248) <br /> stations was used to estimate a rainwater recharge rate. The estimate is based on the average <br /> monthly precipitation of rain fall and evapotranspiration (ETo) for Stockton. The estimate first <br /> determines whether the average monthly precipitation exceeds average monthly ETo. If so, then <br /> the difference is potential deep percolation. This method does not consider runoff. <br /> Table 2. <br /> Estimate of Deep Percolation of Rain <br /> Location Average Deep Percolation of Rain <br /> Stockton Area 2.64 inches per year <br /> Based on this methQd, the average deep percolation of rain for Stockton�is estimated to be <br /> 2.64 inches/year. The)nitrate concentration of rainfall is estimated to be 1 mg/L-N (Hantzsche <br /> and Finnemore, 1992). <br /> 3.3 Current On-Site Sources of Nitrate <br /> The current on-site sources of nitrate include the existing residential septic system and natural <br /> processes. <br /> 3.4 Future On-Site Sources of Nitrate <br /> Based on a review of the site plan, the western portion of the existing agricultural building is <br /> proposed to be developed with a two-story residence. Per information provided by Mr. Solorio, <br /> the proposed addition will include a three bedroom residence and additional septic system. <br /> Therefore, the future on-site sources of nitrate will include the existing residential septic system, <br /> the proposed residential septic system, and natural processes. <br /> 3.5 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 a Resourceful n Reliable 6 <br />