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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 current on-site source of nitrate is the existing house. Because the house will be demolished, however, it is not included in the nitrate loading analysis. One septic system is located on the site; it will likely be demolished along with the house. Three septic permits were identified for the Site from among the San Joaquin County Environmental Health Department permit files (attached): • September 1956 permit for addition of 48-inch diameter by 25-foot deep seepage pit to existing residential septic system; • November 1973 permit for addition of 30-foot leach line and one 33-inch diameter by 25-foot deep seepage pit to existing residential system; • May 2010 permit for replacement septic system utilizing a 1,500-gallon septic tank, two 40-foot leach lines, and two 36-inch diameter by 25-foot deep seepage pits. The future on-site sources of nitrate will be the new septic systems for the proposed houses. • LOGE 1836 Page 6