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LOGE 2126 Page 5 NITRATE LOADING STUDY The method utilized for the nitrate loading analysis is based on a simple and convenient mass balance formula, discussed in a published paper by Hantzsche and Finnemore (1992). Hantzsche and Finnemore have found from investigations conducted in the Chico, California area, the water quality in the upper saturated ground-water zone closely approximates the quality of percolating effluent from septic systems. They have developed a simple method that could be used to estimate the quality of the percolating effluent from septic systems. The quality of the percolating effluent may represent the potential worst-case condition the upper aquifer would experience from the use of on- site septic systems. Mixing and dilution in the aquifer as well as adsorption and adhesion in the soil 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 precipitation of rain. The equation and method are for estimation of long-term effect ground-water quality, and are not intended for prediction of seasonal changes (Hantzsche and Finnemore, 1992). For the purpose of the Hantzsche and Finnemore equation, only septic effluent is included in the nitrate loading calculation; no other potential sources of nitrate are considered. The method takes into account the development area, soil denitrification factor, rainfall recharge rate, rainfall nitrate concentration, waste effluent quantity, and waste effluent nitrate concentration from on-site septic systems. On-Site Sources of Nitrate The septic systems from the existing houses are the current and future source of nitrate on the Site. Live Oak searched the septic system permits on file at the San Joaquin County Environmental Health Department; no permits were identified for the Site addresses. No contribution from any irrigation or soil amendment is considered for the Hantzsche/Finnemore method. It is assumed that any irrigation or soil amendments would be applied at close to agronomic rates for a net balance of plant irrigation and nutrients.