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e LOGE 1907: Bavaro SS/NLS Addendum 3 Page 2 March 15, 2019 adsorption and adhesion in the soil would tend to substantially reduce the concentration of percolating effluent. The Hantzsche and Finnemore equation is a conservative approximation of ground- water nitrate-nitrogen concentration resulting from the combined effect of on-site sewage disposal systems and percolating recharge waters. The equation and method is for estimation of long-term effect ground-water quality, and is not intended for prediction of seasonal changes (Hantzsche and Finnemore, 1992). The method takes into account the development area, soil denitrification factor, rate of recharge from percolating waters, waste effluent quantity, and waste effluent nitrate concentration from on-site septic systems, and predicts the nitrate concentration of percolating effluent. Mass Transport Soil Properties The percolation tests have revealed that the surface soils have good permeability. The soil will allow infiltration of water. The longer the effluent remains near the surface, the more biologic treatment may occur. If permeable soils exist to the 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. First ground water is predicted at 65 to 75 feet below ground surface for this Site; consequently, nitrate reduction would be anticipated as the septic effluent percolates downward. 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 Background 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 discussed, though other downward- percolating waters (including irrigation water and seepage from streams and canals) are known to contribute to recharge as well. In fact, Hantzsche and Finnemore state that "the application of the methods presented in this paper and the reasonableness of the results are ... limited by the accuracy with which the rainfall recharge fraction can be estimated or determined by the user. For best results, the user should perform a thorough water balance analysis."