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depth of the ground -water aquifer, it is possible that any remaining surface contaminants may be transported to the first saturated zone of the aquifer. 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. The Site is located in an area where many orchards have been planted in sandy soil. Percolating Recharge Waters 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, "average recharge rate of rainfall" was utilized. 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). 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. The Site is located closest to the CIMIS stations at Ripon and Manteca. Data from the Ripon station were available for 2017 through 2021; based on the calculation shown, the estimated rate of recharge from percolating waters for the Ripon station is determined to be 2.67 inches (Plate 16). A statistical error of 66 percent is associated with this value. Data from the Manteca station were available for 2014 through 2021; based on the calculation shown, the estimated rate of recharge from percolating waters for the Manteca station is determined to be 3.21 inches (Plate 17). A statistical error of 54 percent is associated with this value. The two stations are then averaged, for a regional rate of recharge of 2.94 inches. Quality of Rainwater Hantzsche and Finnemore listed 1 mg/L-N as the nitrate concentration of rainwater for their original calculation; in the past, Live Oak has also utilized this value for the nitrate loading calculation. To determine a more accurate local value, Live Oak has collected rainwater during several recent storm events in Lodi. Each sample was collected in a clean, dry, LOGE 2233 Page 11