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Sources of Nitrate Dairies, orchards that require fertilization in sandy soils, and septic systems have been found to be the most significant sources of nitrate in ground water. Recharge Rate of Rainfall One of the most determinant factors in the Hantzsche and Finnemore equation is the rate of recharge from percolating waters, which mix with the downward-percolating effluent generated by on-site septic systems. In the original Hantzsche and Finnemore paper, only "average recharge rate of rainfall" was considered. Based on San Joaquin County Environmental Health Department policy (personal communication, March 18, 2019), the recharge input for the Hantzsche and Finnemore equation should be derived from average monthly precipitation of rainfall and evapotranspiration rates for the area; the data should be obtained from the California Irrigation Management Information System (CIMIS), preferably from stations located within San Joaquin County. Recharge is calculated by first determining whether the average monthly precipitation exceeds average monthly potential evapotranspiration. If so, then the difference is the percolating recharge water into the aquifer. Runoff and stream infiltration drainage are not factored into the calculation. This approach likely under-estimates recharge to the aquifer and, consequently, over-estimates nitrate loading. For the project Site, the local percolation and evapotranspiration rates are presented in Plate 12. The Site is located closest to the CIMIS Ripon station (249). Data for the Ripon station were available for 2017 and 2018; based on the calculation shown, the estimated rate of recharge from percolating waters for the Ripon station is determined to be 3.12 inches. A statistical error of 46 percent is associated with this value. Quality of Rainwater Hantzsche and Finnemore utilize 1 mg/L-N as the nitrate concentration of rainwater; in the past, Live Oak has utilized this value for the nitrate loading calculation. In May 2019, Live Oak collected rainwater during two storm events in Lodi; the samples were analyzed for nitrate by FGL Environmental of Stockton. Each sample was collected in a clean, dry, stainless steel bowl, then decanted into a plastic container and placed on ice for transport. Nitrate was detected in the May 17 sample at a concentration of 0.4 mg/L-N and in the May 19 sample at a concentration of 0.2 mg/L-N. The laboratory analytical results are attached as Appendix 6 of this report. Live Oak then averaged the concentrations of the two samples, for a value of 0.3 nig/L-N to represent the nitrate concentration of rain. LOGE 1925 Page 9