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Values and Assumptions: I = 550 gpd x 365 d/v = 200,750 gals/y = 26,838 cu ft = 3.15 in/yr 2.35 Ac x 43,560 sq ft/Ac x (1 ft/ 12 in) Nw = 45 mg N/L d = Assume 33% N reduction in 2,000 gal septic tank and 30% denitrification due to 17% clay content soil. R = 3.78 in/yr. (Table 3) Nb = Assumed to be 0.1 ppm NO3-N 3.15 in/yr (45 mg N/L x (1- 0.33)) = 94.97 x 0 - 0.30) = 66.48 + (3.78 in/yr x 0.1 mg/L) = 9.65 ppm Nr = (3.15 in/yr + 3.78 in/yr) Nr = 9.65 ppm as nitrate -nitrogen (NO3-N) or 43.8 ppm as nitrate (NO3) IV. WASTEWATER TREATMENT SYSTEM - OPERATIONAL CRITERIA SSS§ 3.7. Discussions on the efficient operation of the effluent disposal methods, disposal field longevity, and environmental protection are based upon the parameters discussed within this report. The onsite wastewater treatment system (OWTS) for the proposed three bedroom modular home, is as follows: A 2,000 gallon septic tank is to be installed nearest the influent line from the modular structure. Effluent from this tank gravity flows to a four -hole distribution box. Effluent will then gravity flow equally to three 100 ft leachlines. A. SEPTIC TANK Septic tanks store the accumulated sludge, scum and effluent (clear zone) volumes, which in turn affect treatment of Total Nitrogen (TN) within the tank. Total Nitrogen is the summation of ammonia -nitrogen (NH4) and organic nitrogen (proteins, amino acids, enzymes). Since the septic tank is predominately anaerobic, nitrogen cannot exist in its oxidized state as nitrate (within the septic effluent) for any length of time and is rapidly reduced to NO or NO2- The following calculation illustrates that a 2,000 gallon septic tank will be ample size for sufficient hydraulic residence time (HRT) of influent for the proposed modular home. A septic tank effluent filter shall be installed on the outlet tee of this tank. Detention Time: Detention Time = 2,000 gal total tank capacity x 0.70 (30% volume lost to sludge/scum accumulation) 1.5 (Peaking Factor) x 200 gals/day Detention Time = 4.7 days. The minimum acceptable detention time is 1.0 day. 7 Chesney Consulting