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Soil Suitability 1 Nitrate Loading Study Ehlers Property Lodi, California May 13, 2021 Terracon Project No. NA217019 Irerracon California Irrigation Management Information System (CIMIS) from the Lodi Station (042) and Lodi West Station (166). The estimate first determines whether the average monthly precipitation exceeds average monthly evapotranspiration (ET). If so, then the difference is potential rainfall recharge. This method does not consider runoff, although due to the relatively flat nature of the site, runoff should be minimal. In February 2020, the EHD approved an adjustment to the evapotranspiration (ET) rate based on net rainfall recharge calculation utilizing University of California (UC) plant factors (PF) for established landscape plants. Terracon calculated the ET adjustment factor (actual ET) based on the anticipated commercial landscape. Refer to Appendix F Water Balance Recharge Analysis for monthly precipitation and ET averages. Table 8. Net Rainfall Recharge Based on this method, the average net rainfall recharge for the site is estimated to be 11.55 inches/year. The nitrate concentration of rainfall is estimated to be 1 mg/L-N (Hantzsche and Finnemore, 1992). 2.3.3 Current On -Site Sources of Nitrate The current on-site sources of nitrate include natural processes and the existing septic systems. 2.3.4 Future On -Site Sources of Nitrate Future on-site sources of nitrate include the existing septic systems and natural processes. 2.3.4.1 Quantity and Quality of Wastewater from Project Refer to Section 1.1 and 1.3.7 for further discussion regarding usage rates quantities selected. The average total nitrogen concentration of domestic wastewater is normally considered to be 20 to 85 mg/L-N with 35 to 45 mg/L-N being typical (Crites and Tchobanoglous, 1998). It is estimated that commercial use will have higher concentrations of total nitrogen when compared to residential use. For the purposes of the nitrate loading estimate, it is estimated that the average concentration for total nitrogen in wastewater for the project is approximately 85 mg/L-N over the long term. Responsive n Resourceful ■ Reliable 14 ET Net Rainfall CIMIS Station Average Precipitation Potential ETO s Adjustment t Actual ET Recharge Number/ Location (in/year) (in/year) Factor (in/month) (in/year) 042/Lodi 15.46 50.50 0.175 8.84 11.55 166 Lodi West Based on this method, the average net rainfall recharge for the site is estimated to be 11.55 inches/year. The nitrate concentration of rainfall is estimated to be 1 mg/L-N (Hantzsche and Finnemore, 1992). 2.3.3 Current On -Site Sources of Nitrate The current on-site sources of nitrate include natural processes and the existing septic systems. 2.3.4 Future On -Site Sources of Nitrate Future on-site sources of nitrate include the existing septic systems and natural processes. 2.3.4.1 Quantity and Quality of Wastewater from Project Refer to Section 1.1 and 1.3.7 for further discussion regarding usage rates quantities selected. The average total nitrogen concentration of domestic wastewater is normally considered to be 20 to 85 mg/L-N with 35 to 45 mg/L-N being typical (Crites and Tchobanoglous, 1998). It is estimated that commercial use will have higher concentrations of total nitrogen when compared to residential use. For the purposes of the nitrate loading estimate, it is estimated that the average concentration for total nitrogen in wastewater for the project is approximately 85 mg/L-N over the long term. Responsive n Resourceful ■ Reliable 14