SU0002188_SSNL - Laserfiche WebLink

Home Browse Search

o October 4,-tool - Octo Job Number:LG00-287 i Page 10 y the subject parcel. If.a.site.is.contributing excess nitrogen to ground water, ground water quality can be impacted. The nitrate sources considered for this project are percolating septic effluent from proposed facility, and deep percolation of rain water containing nitrate.. The method utilized in this analysis isbased 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 groundwater 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 their approach is a good planning tooLand 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 l ' nitrate-nitrogen concentration of ground-water flow from up-gradient areas is.lower.". The Hantzsche and Fennerriore equation'provides"...a conservative(worst case) first f 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. iL estimation of long-term effect(i.e., over years) on ground-water quality, and is not intended for prediction:of seasonal-changes." The Haritzsche and Fennemore7 equation takes into account development area,soil . denitrification 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 1.0 mg/l. ; Nitrates from Septic System The average nitrate concentration of the typical septic waste is normally'considered to be ( s 45 mg/L-N (Not to be confused with the MCL for drinking water of 45 mg/L-NOD., To Hantzshe N.N:,:Finnemore,E.J. 1991,Predicating,Ground-WaterNitrate-Nitrogen Impacts. Ground Water,Vol. 30,No.4. " s Otis,RJ.,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). Z