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• ' r VILQM^ Htice Lee Sts-sse-Oo. 0706 P . 5/6p. 4 <br /> .��tjj'�j�j�+ � <br /> a7li..+.[ ''!'l.'i L SfL Project No. 0 ndbi D <br /> TOO&W, f a� Appendix D <br /> Page t).2 <br /> There is a 20 porcent removal of nitrogen in the septic tattle before discharge to the leach field <br /> (Kaplan, O. Benjamin, Septic Systems Handbook page 148, 1988, Lewis Publishers) <br /> Denitrification is the process by which nitrogen gas is released into the environment as bacteria <br /> consumes the oxygen available from nitrate in the effluent Denitrification is expressed as a percent of <br /> the original conoentratioo of nitrogen in the matrix. Soils with high erganio contents, high pH, sad <br /> high moisture contents, typically clays denitrify about 35 percent on the high end. Sandy soils with a <br /> high percolation rate denitrify at a much lower rate, on the order of 10 to 15 percent. We have <br /> assumed a denitrification factor of 15 percent <br /> The average precipitation in the region is around 17 inches per year. The background concentration of <br /> rainwater was estimated at 0.17 mgtL N, based on the values provided by HantTsche and Finnemore, <br /> 1991, <br /> Waste Loadimr Calculation! <br /> l=(310gaVday)(1cf77.48gal)(16.5persons/4acresxlacre/43,560012in/ft)(365day/year) <br /> I= 17.2 inch/year <br /> Nw=(I Sg/dayperson)(i,000mg/0(0.9—20%reduction in tank)(80gpd)(1 gal/3.78L) <br /> Nw-- 40mg/L as N <br /> Combined Loading Calculation: <br /> Nc-- [(17.2 in/ymX40mg/L as N)(1-0.15)-+ (l7 in7ym)(.t7mg/L-N)]/(17.2in/yr+ 17 in/yr) <br /> Ne = 17 mg(L as N (greater than MCL= 10 mg/L as N) <br /> The results of the analysis indicate that a specifically designed septic system will be required to handle <br /> the anticipated effluent without significant risk of the development of methemoglobinemia. This <br /> conclusion is based solely upon the dwee of accuracy for the method of detamtination and the <br /> assumptions utilized therein. <br /> 7 <br />