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Soil Suitability / Nitrate Loading Study <br /> 11065 North Alpine Road I Stockton, California r rerracon <br /> June 30, 2026 1 Terracon Project No. NA267068 <br /> Table 9 <br /> Net Rainfall Recharge <br /> CIMIS Station Average Precipitation Potential ETO ET Actual ET Net Rainfall <br /> Number/ Adjustment Recharge <br /> Location (in/year) (in/year) Factor (in/year) (in/year) <br /> 262/Linden 15.51 53.37 0.38 20.28 5.74 <br /> Based on this method, the average net rainfall recharge for the site is estimated to be <br /> 5.74 inches/year. <br /> The nitrate concentration of rainfall is estimated to be 1 mg/L-N (Hantzsche and <br /> 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, natural <br /> processes, and agricultural practices. <br /> 2.3.4. Future On-Site Sources of Nitrate <br /> Future on-site sources of nitrate will include a proposed septic system, the existing <br /> septic system, natural processes, and agricultural practices. <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 <br /> from the proposed development for the nitrate loading analysis and should not be used <br /> for septic system design purposes. Typically, use estimates for septic system sizing <br /> include a peak use factor. <br /> The total maximum daily flow rate for the proposed septic system is 420 gpd (see <br /> section 1.3.7). In February 2020 (SR0081473), the EHD approved a revised calculation <br /> method for long-term average discharge of wastewater and recommended using 100 gpd <br /> for the 1st bedroom plus 50 gpd for each additional bedroom in the Hantzsche/Finnemore <br /> equation. Therefore, we will utilize 200 gpd. <br /> The average total nitrogen concentration of domestic wastewater is normally considered <br /> to be 20 to 85 mg/L-N with 35 to 45 mg/L-N being typical (Crites and Tchobanoglous, <br /> 1998, Table 4-14). It is estimated that commercial use will have higher concentrations <br /> of total nitrogen when compared to residential use. For the purposes of the nitrate <br /> loading estimate, an estimated average concentration for total nitrogen in wastewater <br /> for the project is approximately 45 mg/L-N. <br /> Facilities I Environmental I Geotechnical I Materials 17 <br />