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MOUND DESIGN WORKSHEET \ (For flows up to 1200 gpd) MOUND B ' 375 gpd or measured X 1.5 = gpd B. SEPTIC TANK LIQUID VOLUMES: 2 - 1250's C. SITE EVALUATION INFORMATION 1. Depth of clean sand req. 20.00 inches or 1.67 feet 2. Depth of percolation tests = 12 inches 3. Perc. Rate 23 mpi 4. Land Slope 3.0 percent D. ROCK LAYER DIMENSIONS 1. Multiply flow rate by 0.83 to obtain required area of rock layer: 375 gpd X 0.83 sq ft/gpd 311.25 sq. ft. rock area 2. Select width of rock layer (Max 10' if<120, or max 5' if>120) 10.0 eet 3. Rockbed length (area/width) 311 sq. ft. I 10.0 feet = 33 feet E. ROCK VOLUME 1. Multiply rock area by rock depth to get cubic feet of rock: 311.25 sq. ft X 1.0 = foot = 311 cubic feet 2. Divide cubic feet by 27 to get cubic yards: 311 cu. ft. / 27 = 11.5 cubic yards 3. Multiply cubic yards by 1.4 to get weight of rock in tons: 11.5 cu. yd. X 1.4 = 16.1 tons X 10 % = 20.2 ton req'd F. ADSORPTION WIDTH 1. Percolation rate in top 12 inches of soil is 23.0 m i Soil Texture is SICL ISize for Clay Loam 2. Select allowable soil loading rate from table: 0.45 gpd / sq. ft. PEC RATE MPI SOIL TEXTURE GPD I SQ.FT. RATIO FASTER>0.1 COARSE SAND 1.20 1.00 0.1 TO SAND 120 1,00 0.1 TO 5 FINE SAND 0.60 2.00 6 TO 15 SANDY LOAM 0.79 1.52 16 TO 30 LOAM 0.60 2.00 31 TO 45 SILT LOAM 0.50 2.40 46 TO 60 CLAY LOAM 0.45 2.67 60 TO 120CLAY 0.24 5.00 - >120 CLAY 0.20 6.00 3. Calculate adsorption width ratio by dividing rock layer loading rate of 1.20 gpd / sq. ft. by allowable soil loading rate.- 1.20 ate:1.20 gpd/ sq. divided by 0.45 gpd / sq. ft. equals 2.67 4. Multiply adsorption width ratio by rock layer width to get required adsorption width- 2.67 X 10.0 feet = 27 feet adsorption width additional feet added.