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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 article 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 ever 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). 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 system from the existing house is the current on-site source of nitrate. One septic permit was identified for the Site from among the San Joaquin County Environmental Health Department permit files; two additional permits which could refer to the Site are attached as well: • May 1960 permit for new residential septic system. The permit indicates a 1,000- gallon septic tank, an 80-foot leach line, and a 33-inch diameter by 15- to 20-foot deep seepage pit. The address listed is 11860 Valpico. • July 1985 permit for repair to leach line at residential septic system. • June 2005 permit for addition of 30- by 40-foot filter bed to existing residential septic system. The address listed is 11850 W. Valpico; the owner is listed as Ricardo and Irene Marrun (subject Site). These permits have been attached to this report. LOGE 1840 Page 6