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x <br /> rFD. CAILCULATED IMPACT FROM NITRATE-NITROGEN LOADING <br /> The calculated (or estimated) nitrate impact to the soil and ultimately to the groundwater is extremely <br /> difficult to determine due to the number of variables involved. The following calculations are based <br /> on using a conventional or traditional type of septic system consisting of two septic tanks, leachf eld <br /> and seepage pits. <br /> HANTZSCHE/FINNEMORE EQ UA TION FOR SEPTIC SYSTEM IMPA CT <br /> IN,v(1 -d)+RNb <br /> Nr= (I+ R) <br /> Where: <br /> Nr= Resultant average concentration of nitrate-nitrogen in recharge water-(ppm NO,-N) <br /> f I = Volume rate of wastewater entering the soil averaged over the gross developed area in <br /> + } inches per yr <br /> Nw= Total nitrogen concentration of wastewater in N mg/L (66 mg N/L/day) <br /> d = Fraction (%) of nitrate-nitrogen loss due to denitrification in the soil <br /> R = Average recharge rate of rainfall -inches per yr(13) <br /> Nb= Background nitrate-nitrogen concentration of rainfall recharge, exclusive of wastewater <br /> influences (pprn NO,-N) <br /> Values and Assumptions <br /> F <br /> 68 gals/person/day x 4 people per household x 3 new houses+ 1 existing house/7.32 Ac x 365 d/yr=2.00 in/yr. <br /> 1= 43,560 cu ft/Ac ft x 7.48 gal/cu ft x (1 ft/12 in) <br /> Nw = 66 mg/L- 20% reduction from two septic tanks in series = 53 mg/L N <br /> I <br /> d 10% from biomat and 15% from saturated clay soil conditions under leachlines and seepage pits. <br /> Nb = Assumed to be 0.1 ppm NO3-N <br /> F,' <br /> 2.00 in/yr(53 mg N/Q (1 - 0.25) + (13.5 in/yr x 0.1_mg/L) <br /> Nr = (2.00 in/yr+ 13.5 in/yr) <br /> �f Nr = 5.2 ppm as NO3-N or 23.2 ppm as NO3 <br /> Y <br /> J]I� <br /> t� ' <br /> 4 <br /> 9 <br /> I , <br /> Chesney Consulting <br />