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Nitrate Loading Study Irerracon Roque Property® Victor, California July 6, 2018 ■Terracon Project No. NA187032 3.2 Contribution of Rainfall An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. The estimate of deep percolation of rain is based on the average monthly precipitation of rain fall and evapotranspiration near Lodi, California. The estimate first determines whether the average monthly precipitation exceeds average monthly potential evapotranspiration. If so, then the difference is potential deep percolation. This method does not consider runoff, although due to the relatively flat nature of the site, runoff should be minimal. Average precipitation and potential evapotranspiration were obtained from the California Irrigation Management Information System (CIMIS)website and the Western Regional Climate Center. Refer to Appendix B for the data and calculation. Table 1. Estimate of Deep Percolation of Rain for the Site Location Deep Percolation of Rain Lodi 5.76 inches per year Based on this method, the average deep percolation of rain for the Lodi area is estimated to be 5.76 inches/year. The nitrate concentration of rainfall is estimated to be 1 mg/L-N (Hantzsche and Finnemore, 1992). 3.3 Current On-Site Sources of Nitrate We understand the site is developed with an existing two bedroom residence and septic system; therefore, the current on-site sources of nitrate include the existing septic system and natural processes. No additional sources of nitrates besides septic effluent, groundwater, and rainfall are anticipated. 3.4 Future On-Site Sources of Nitrate We understand the site is proposed to be developed with a two bedroom mobile home and additional septic system. Therefore, the future on-site sources of nitrate will include the existing septic system, the proposed additional septic system, and natural processes. 3.5 Quantity and Quality of Wastewater from Project The following discussion is for determining the long-term wastewater flow generated from the proposed development for the nitrate loading analysis and should not be used for septic system design purposes. Typically, use estimates for the sizing of septic systems include a peak use factor, whereas the numbers discussed here are based on long-term averages. The estimated sewage flow rates for use categories are available from a number of references. The uses presented below were guided by the San Joaquin County On-Site Wastewater Disposal Responsive■ Resourceful ■ Reliable 5