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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 OWTS for the proposed three bedroom structure, is as follows: 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 1,200 gallon septic tank will be ample size for sufficient hydraulic residence time (HRT) of influent for the proposed three bedroom modular home. Detention Time: Detention Time = 1,200 gal total tank capacity x 0.70 (30% volume lost to sludge/scum accumulation) 1.5 (Peaking Factor) x 420 gals/day Detention Time = 1.2 days. The minimum acceptable detention time is 0.5 day. The calculated detention time is based on using an exorbitant flow volume of 420 gpd (70 gpdpc x 2 people/bedroom = 140 x 3 bedrooms = 420 gpd), as described in the USEPA Manual. A reasonable flow volume of 210 gpd yields a detention time of 2.6 days. B. LEACHFIELD REQUIREMENTS FOR THE PROPOSED THREE BEDROOM MODULAR HOME: Since the percolation test result was acceptable and the nitrate loading was determined to be under the MCL, a conventional OWTS can be installed for this project. The subject property is located in an area designated by EHD as "High Water -Table Areas." The requirement is a 1,200 gallon septic tank and 100 lineal ft of leachline (LFLL) per bedroom = 300 LFLL. If a filter bed disposal configuration is decided upon, the area would equal 300 x 4 = 1,200 sq ft. C. SETBACKS FROM DOMESTIC WELLS The attached aerial photo illustrates the well distances from the SFR adjacent to the south (Mrs. Erskine's parents home) and the recently drilled domestic well for the subject property located near the north property line. 7 Chesney Consulting