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the surface, the more biologic treatment may occur. If permeable soils exist to the depth <br /> of the ground-water aquifer, it is possible that any remaining surface contaminants may <br /> be transported to the first saturated zone of the aquifer. <br /> Sources of Nitrate <br /> Dairies, orchards that require fertilization in sandy soils, and septic systems have been <br /> found to be the most significant sources of nitrate in ground water. <br /> Percolating Recharge Waters <br /> One of the most determinant factors in the Hantzsche and Finnemore equation is the <br /> rate of recharge from percolating waters, which mix with the downward-percolating <br /> effluent generated by on-site septic systems. In the original Hantzsche and Finnemore <br /> paper, "average recharge rate of rainfall" was utilized. <br /> Based on San Joaquin County Environmental Health Department policy (personal <br /> communication, March 18, 2019), the recharge input for the Hantzsche and Finnemore <br /> equation should be derived from average monthly precipitation of rainfall and <br /> evapotranspiration rates for the area; the data should be obtained from the California <br /> Irrigation Management Information System (CIMIS). Recharge is calculated by first <br /> determining whether the average monthly precipitation exceeds average monthly <br /> potential evapotranspiration. If so, then the difference is the percolating recharge water <br /> into the aquifer. Runoff and stream infiltration drainage are not factored into the <br /> calculation. This approach likely under-estimates recharge to the aquifer and, <br /> consequently, over-estimates nitrate loading. <br /> The Site is located closest to the CIMIS station at Staten Island (station 242). Data for <br /> the Staten Island station were available for the past four years; based on the calculation <br /> shown, the estimated rate of recharge from percolating waters for the Staten Island <br /> station is determined to be 11.78 inches (Plate 13). A statistical error of 45 percent is <br /> associated with this value. <br /> Quality of Rainwater <br /> Hantzsche and Finnemore listed 1 mg/L-N as the nitrate concentration of rainwater for <br /> their original calculation; in the past, Live Oak has also utilized this value for the nitrate <br /> loading calculation. <br /> In May 2019, Live Oak collected rainwater during two storm events in Lodi; in March <br /> and May 2020, Live Oak collected two additional samples at the same location. Each <br /> sample was collected in a clean, dry, stainless steel bowl, then decanted into a plastic <br /> LOGE 20-36 <br /> Page 9 <br />