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December 23,2002 Job Number: LG02492 Page 7 L proposed facility, deep percolation of rain water containing nitrate, agricultural fertilizers, and winery waste. L The method utilized in this analysis is based on a simple mass balance formula discussed in a published article by Hantzsche and Finnemore'that provides a convenient and simplified method to estimate long-term ground-water nitrate impacts on an area-wide basis. Hantzsche and Finnemore found that over a long period of time,water quality in the upper saturated ground- water zone closely approximates the quality of percolating recharge waters. They have found that L their approach is a good planning tool and provides useful information to planners and local officials but with some real limitations. In Hantzsche and Fennemore's article, published in Ground Water, they mention that"...the equation ignores dispersion, lateral flow, and mixing ` with ground water flow from up-gradient areas. These processes would generally contribute to additional reduction of nitrate-nitrogen concentrations in ground water to the extent that the ` nitrate-nitrogen concentration of ground-water flow from up-gradient areas is lower." The Hantzsche and Fennemore equation'provides"...a conservative(worst case) first ` approximation of ground-water nitrate-nitrogen concentration resulting from the combined effect of on-site sewage disposal systems and precipitation. This (the equation and approach) is for estimation of long-term effect(i.e., over years) on ground-water quality, and is not intended for prediction of seasonal changes." The Hantzsche and Fennemore' equation takes into account development area, soil denitrification 6- factor,rainfall volume, rainfall nitrate concentration, the waste effluent quantity, and waste effluent nitrate concentration. The formula, assumptions and calculations used for the analysis are shown on Plates 8 and 9. The units of nitrate used in the mass balance equation are nitrate-N whose maximum drinking water contaminate level is 10 mg/L. 5.1 Nitrates from Septic System and Rain Fall 6. The total average nitrate concentration of the typical septic waste is normally considered to be 45 ` mg/L-N 8 (This concentration is not related to the maximum contaminate level for drinking water L ' Hantzshe N.N.,Finnemore,E.J. 1991,Predicating Ground-Water Nitrate-Nitrogen Impacts. Ground Water,Vol.30,No.4. L 8 Otis,M.,Boyle,W.C., 1980,Design manual,onsite wastewater treatment and disposal systems:U.S. Environmental Protection Agency,EPA 625/1-80-012. (See page 100,table 6-1). L 'VE�Spi