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� • . <br /> 01/08/2003 Page 1 <br /> � <br /> Mound Design Worksheet <br /> � (FOR FLOWS UP TO 1200 GPD) <br /> A. Estimated gpd= 750 <br /> � B. SEPTIC TANK CAPACITY; 2000 gallons . <br /> � C1. Depth to restricting layer- 24 in h s <br /> 2. Depth of percolation tests= 14 inches <br /> 3. Percolation rate= 20 � <br /> � 4. Land slope= 5 % <br /> D1. Multiply flow rate (A) b� 0.83 sq.ft./gpd to obtain required area of rock layer: <br /> � A x 0.83 = 750 gpd x 0.83 = 622.0 sq.ft. <br /> 2. Select width of rock layer (10 feet or less) = 10 ft. <br /> � 3. Length of rock layer-area/width = 63 ft. <br /> E1. Multiply rock area by rock depth to get cubic feet of rock: <br /> � 622 sq.ft. x 0.9 ft. = 559.8 cu.ft. + 56.0 cu.ft. for tapering <br /> 2. Divide cu.ft. by 27 cu.ft./cu.yd. to get cubic yards: <br /> 615.8 cu.ft. /27 = 22.g cu yd <br /> � 3. Multiply cubic yards by 1.4 to get weight of rock in tons: <br /> 22.8 cu.yd. x 1.4 ton/cu.yd. = 31.9 ns. <br /> � F1. Percolation rate in top 12 inches of soil = 2p mpi. <br /> 2. Select allowable soil loading rate from table: 0.45 dgp /sq.ft. <br /> 3. Calculate adsorption width �atio by dividing rock layer loading rate . <br /> � of 1.20 gpd/sq.ft. by allowable soil loading rate: ; <br /> 1.20 gpd/sq.ft. / 0.45 gpd/sq.ft.= 2.67 sc�/ft/pallon <br /> 4. Multiply adsorption width ratio by rock layer width to get required <br />� adsorption width 2.67 x 10 ft. = 26.7 ft. <br />� Absorption Width Sizing <br /> Perc rate Soil Gpd Ratio of absorption width <br /> m� Texture Sa/ft to rock layer width <br />� 0.1-5 fine sand 0.60 2.00 <br /> 6-15 sandy loam 0.79 1.52 <br /> 16-30 loam 0.60 2.00 <br />� 31-45 silt loam 0.50 2.40 <br /> 46-60 clay loam 0.45 2.67 <br /> 60-120 clay 0.24 5.00 <br />� >120 clay 0.20 6.00 <br />� <br />� <br />