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B. FILTER BED DESIGN AND EFFLUENT ACCEPTANCE The configuration of the disposal structure can be two methods: leachline trench to a maximum 24 inches wide and maximum 42 inches deep, or a filter bed arrangement. The calculations are as follows for leachlines: 1,200 gallon Base Tank Capacity(BTC)+Average Daily Flow(ADF)= 1,200+210 gpd= 1,410 gals. 1,410 gals x 0.225 (SF) =317 lineal ft of leachline (LFLL). The Site Plan indicates two - 85 ft leachlines for a total of 170 LFLL. Therefore, a filter bed arrangement should be considered: 317 LFLL x 4 = 1,268 sq ft of calculated filter bed area. The illustrated primary disposal area consists of: 20 ft x 85 ft= 1,700 sq ft. QQ The proposed filter bed dimensions can be 10 ft wide x 85 ft long= 850 sq ft, and 1 ft deep. The entire I ft depth must be installed below the clay layer that exists from 0-2.5 ft. Using a filter bed depth of 1 ft, we find the entire filter bed has an effluent acceptance area of. 1 + 10 + 1 x 85 = 1,020 sq ft. The acceptance rate correlated with the observed perc rate as referenced on Page 3 is determined to be 0.671 gals/sq ft/day. Therefore,the filter bed soils will theoretically accept 1,020 sq ft x 0.671 gals/sq ft/day=684 gpd. The septic tank, primary and sufficient 100% replacement areas are denoted on the attached Site Plan produced by Haggerty Construction. Influent will enter the tank, which will be situated northeast of the guard house. Effluent gravity flows from the septic tank, into a distribution box (D-box - not shown),then enters two, 3-inch dia. perforated laterals capped at the ends that run level. This will allow equal gravity distribution of effluent throughout the filter bed. The laterals should be equal distance apart within the filter bed area. V. CONCLUSIONS AND RECOMMENDATIONS SS S§ The surface and shallow subsurface soils underlying the subject property where the prop se filter bed is to be installed, reveals a medium permeability. There is a change in soil structure at approximately 2.5 ft below grade from a an/heavy clay to a clay loam. The filter bed soils can theoretically accept 684 gals/day. The ADF was determined to be 210 gpd. However, advanced biomat formation will impede the permeability of the receiving soils to an indeterminable extent. A decrease in soil permeability of 50%can be considered plausible. Consequently,the receiving soils with a mature biomat may manage: 1,020 sq ft x 0.671+2 gals/sq ft/day= 342 gals/day. NLS The nitrate loading calculations show the resultant effluentfrome subject property will theor ally possess a_nitrate-nitrogen concentration of approximately 2.6 ppin which is approximately one-fourth the Federal nitrate Maximum Contaminant Level (MCL). r ` l NLS 4, , SSS§ �7. All decentralized wastewater management systems (septic systems)will eventy fail. A reasonable lifespan for the primary area system can be expected based on the proposed components of the septic system, equal distribution of effluent,and the indigenous clay loam soil structure with an acceptable permeability. This lifespan can be measured in years. 8