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r�� <br /> Where: <br /> i <br /> Nr = Resultant average concentration of nitrate-nitrogen in recharge water-(ppm NO3-N) <br /> I = Volume rate of wastewater entering the soil averaged over the gross developed area in inches per yr <br /> Nw = Total nitrogen concentration of wastewater in mg N/L <br /> d = Fraction(%)of nitrate-nitrogen denitrified. <br /> R = Ave. recharge rate of rainfall -inches per yr From San Joaquin County Isohyetal map.NLS§3.2 <br /> Nb = Background nitrate-nitrogen concentration of rainfall recharge, exclusive of wastewater influences <br /> (ppm NO3-N)- <br /> Values and Assumptions: <br /> I=9,984 gals=total WW/yr=1,335 cu ft =0.00547 in/yr <br /> 67.19 Ac x 43,560 sq ft/Ac x(1 ft/12 in) <br /> Nw= 62 mg N/L <br /> d = Assume 10%due to the low percentage of clay soil at the soil-effluent interface. <br /> R = 9.5 in/yr. <br /> Nb= Assumed to be 0.1 ppm NO3-N <br /> 0.00547 in/,3r((62 mg N/L) (1 -0.10)+(9.5 in/yr x 0.1 m /g_L) <br /> Nr = (0.00547 in/yr+9.5 in/yr) <br /> Nr = 0.132 ppm as nitrate-nitrogen(NO3-N), <br /> IV. SEPTIC SYSTEM DESIGN: OPERATIONAL PARAMETERS AND COMPONENTS <br /> A. SEPTIC TANK <br /> Septic tanks store accumulated sludge, scum and effluent(clear zone)volumes, which in turn affect <br /> treatment of nitrogen within the tanks. Detention time calculations demonstrate that when the <br /> maximum ADF is applied to the existing tank,there remains ample detention time: <br /> Detention Time Calculation: <br /> Detention Time= 1,200 gal tank capacity x 0.70(30%volume lost to sludge/scum accumulation) <br /> 1.5 (Peaking factor)x 32 gals/day(ADF) <br /> Detention Time= 17.5 days.The minimum acceptable detention time is 1.0 day. <br /> B. FILTER BED SIZING CALCULATIONS <br /> Base Tank Capacity(BTC)= 1,200 gal. Leachline Equivalent Requirement= 1,200 gallons BTC+ 32 gpd <br /> ADF x 0.200 sandy loam Soil Factor(SF)=246 lineal feet of Leachline(LFLL). <br /> 246 LFLL x 3 (Filter Bed Soil Factor)=740 sq ft. Filter bed is to be rectangular: 37 ft E-W,20 ft N-S. <br /> Pae -6- <br /> Chesney Consulting <br />