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water aquifer, it is possible that any remaining surface contaminants may be transported to the first saturated zone of the aquifer. Clay soils, like those found on this Site, also 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. 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, 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. The project Site is located relatively far from any CIMIS stations (10.3 and 12.2 miles to the closest stations within San Joaquin County) but closer (7.5 miles) to a station monitored by the Western Regional Climate Center (WRCC). As a result, two scenarios have been run for the Site, the first using strictly CIMIS data, and the second using a combination of CIMIS and WRCC data. Recharge Scenario 1 — CIMIS Ripon & Holt Stations For the CIMIS-only scenario, the local percolation and evapotranspiration rates obtained through CIMIS are presented in Plates 12 and 13. The closest CIMIS stations to the Site are Ripon (249) and Holt (248), located approximately 10.3 and 12.2 miles away, respectively. Data for these stations were available for 2017, 2018, and 2019. Based on the calculation shown, the estimated rate of recharge from percolating waters for the Ripon station is determined to be 3.00 inches (Plate 12); the estimated rate of recharge LOGE 20-48 Page 9