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is q PRESSURIZED FILTER BED SIZING CALCULATIONS Base Tank..Capacity= 1,200 gal (always used) Base Tanki,Capacity(BTC) +Average Daily Flow(ADF)x Soil Factor(SF)_ 1,200 gal BTC +700 gal ADF x .250 SF (Clay Soil) =475 lineal feet of leachline.(LFLL) 475 x 4 (Clay Soils)= 1,900 sq. ft. filter bed area. Proposed filter bed area=40 ft E-W wide x 50 feet N-S length=2,000 sq. ft. 8 Infiltrator Chambers N-S x 6.25 ft length/chamber=50 ft N-S M 12 Infiltrator Chambers E-W x(2.83 ft+0.5 ft spacer)= 3.33 ft width/Chamber=40 ft E-W. Therefore,'�a total of 8 x 12 = 96 Standard Infiltrator Chambers SC (Shallow Cover) are required. 100% Replacement Area: Use of existing leachfield: Approximately 25 ft E-W x 100 ft N-S = 2,500 sq. ft. The triangular area in the extreme SWC or the property can also be reserved and activated for a replacement area: 0.5 x 35 ft x 80 ft = 1,400 sq. ft. .i IV. CONCLUSIONS AND RECOMMENDATIONS A nitrate concentration of 259 ppm, determined in the water table under the existing leachfield at the west end of the subject facility, has precipitated the decision by EHD to place the entire complex on the proposed pressurized filter bed system as designed in this report. The water table nitrate concentration of 56 ppm upgradient to this leachfield indicates that the existing leachfield is the source of the nitrate contamination. The percolation rates obtained indicate a marginally acceptable soil permeability with the permeability decreasing as the soil becomes saturated. Effluent management, and therefore design criteria should be based on the permeability of the soil eventually reaching a long term application rate (LTAR) of approximately 0.2 to 0.5 gals/ft'/day due to biomat formation. h Several scientific studies have demonstrated that the infiltration capacity of a soil absorption system is dependant primarily by the formation of the biomat and not by the permeability of the soil. The-biomat is a biological, slimy substance which forms on the soil-effluent interface over time. Effluent hydraulic loading rates under equilibrium conditions range from a conservative criterion of 0.125 gal/ft /day to 0.5 gal/ft'/day. The actual infiltrative surface (IS) under the hifiltrator'Chambers is 6.25 ft x 2.83 ft = 17.69 ft . 17.69 ft' x 96 Standard Infiltrator Chambers SC = 1,700 W. If the Average Daily Flow is taken to be 345 gals/day based on the anticipated daily number of people on-site, the Long-term Application Rate (LTAR) = 345 _ 1,700 = 0.20 gals/ft'/day. The designed Chambered filter bed that will be placed high in elevation will take advantage of the indigenous clay soils that will inhibit nitrification, and for the nitrification that does occur, the clay soils'should promote denitrification. This was apparently evidenced by the soil test results under the!proposed and existing disposal fields. The denitrification potential in combination with landscape grass in the filter bed area should also reduce nitrate impact by evapotranspiring a percentage of the effluent through the louvers during favorable weather times of the year. 15 Chesney Consulting