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of the ground-water aquifer, it is possible that any remaining surface contaminants may be transported to the first saturated zone of the aquifer. Clay-containing soils, like those observed on the Site, tend to inhibit downward movement of nitrate due to adsorption of the nitrate ions to the soil. 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 within a residential neighborhood that relies on septic systems; orchards lie to the east, west, and north of this neighborhood. 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), 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. The project Site is located relatively far from any San Joaquin County CIMIS stations (13.5 and 14.2 miles to the closest stations) but considerably closer (5.2 miles) to a station monitored by the Western Regional Climate Center (WRCC). In addition, the CIMIS stations are located east and northeast of the Site, while the WRCC station is located northwest of the Site; as a result, data from the two sources have been averaged to present a reasonable representation of rainfall levels near the Site. CIMIS Holt and Ripon Stations For the CIMIS data, the local precipitation and evapotranspiration rates obtained through CIMIS are presented in Plates 15 and 16. The closest San Joaquin County CIMIS stations to the Site are Ripon (249), located approximately 13.5 miles east of the LOGE 2637 Page 9