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\/`I V %/ F he/Finnemore Equation is used below to estimate the resultant average nitrate-nitrogen n in the effluent recharge water at a maximum volume of 1,000 gpd with a Total ncentration of 103 mg N/L: HE/FINNEMORE EQUATION INW,(1 - d) +RNh Nr= (I + R) Where: Nr= Resultant average concentration of nitrate-nitrogen in recharge water- (ppm NO3-N) I = Volume rate of wastewater entering the soil averaged over the gross developed area in inches per yr. Total area of subject property =6.2 ac. Nw= Total Nitrogen concentration of wastewater in mg/L (103 mg N/L) d = Fraction(%) of nitrate-nitrogen loss due to denitrification in the soil (15%) R = Average recharge rate of rainfall - inches per yr(11 in.) Nb= Background nitrate-nitrogen concentration of rainfall recharge, exclusive of wastewater influences (ppm NO3-N) Values and Assumptions: 1,000 gals/day x 255 workday/yr=255,000 gals/vr=34,090 cu ft WW/vr = 1.5 in/yr I= 43,560 cu ft/Ac ft x 6.2 Ac x (1 ft/12 in) Nw= 103 mg N/L -nitrogen reduction in the septic tanks= 15%with two tanks= 88 mg N/L d = 10% from biomat formation and 15% (=25%) from clay content in soil and the use of peat under laterals. Nb = Assumed to be 0.1 ppm NO3-N 1.5 in/vr(88 mg N/L) (1 - 0.25) + (11 in/yr x 0.1 m¢/L) Nr = (1.5 in/yr+ 11 in/yr) Nr = 8.0 ppm as NO3-N or 35.6 ppm as NO3 C. Wastewater Disposal System Design Specifications Septic Tanks Influent from the three buildings will gravity flow into two separate - 2,000 gallon tanks in series. If it is determined in the future, after the project is completely built-out, that there must be additional nitrate impact mitigation, these two septic tanks may have to be replaced with nitrate treatment systems. Sufficient area must be reserved for this possibility. Pressurized effluent will be pumped to the filter bed for disposal. Effluent filters, such as Orenco's BioTube effluent filter vault or a Zabel filter will be required in the second tank. Za . Page -8- Clresney Consulting