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MOUND DESIGN WORK SHEET(For Flows up to 1200 gpd) _ <br /> A. Average Design FLOW <br /> A-1: Estimated Sewage Flows in Gallons per Day <br /> number of <br /> Estimated 1.I,0 gpd (see figure A:1) bedrooms Class I Class II Class Ill Class IV <br /> or measured — x 1.5 (safety factor) = gpd 2 300 225 180 60% <br /> 3 450 300 218 of the <br /> 4 600 375 256 values <br /> B. SEPTIC TANK Capacity 5 750 450 294 in the <br /> 6 900 525 332 Class I, <br /> a—i gallons (see figure C-1) 7 1050 600 370 II, or Ill <br /> 8 1200 675 408 columns. <br /> C. SOILS (refer to site evaluation) C-l: Septic Tank Capacities(in Ballon) <br /> Liquid capacity <br /> Number of Minimum Liquid Liquid capacity with with disposal& <br /> 1. Depth to restrictinglayer = a.o t ..3Capacity g <br /> feet Bedrooms arbage disposal <br /> Pa ylift inside <br /> 2. Depth of percolation tests = /. 6 feet 2 or less 750 1125 1500 <br /> 3. Texture c.L.)V. 40 r07\ 3 or 1000 1500 2000 <br /> 5 or 1500 2250 3000 <br /> Percolation rate ))...0 mpl 7,8 or 9 2000 3000 .114 <br /> 4. Soil loading rate .4.S--- gpd/sqft (seep figure D-33) <br /> 5. Percent land slope_ 1 % ! <br /> D. ROCK LAYER DIMENSIONS <br /> 1. Multiply average design flow (A) by 0.83 to obtain required rock layer area. <br /> 1ç3gpd x 0.83 sqft/gpd 30 z� ;sgft-a l0°20 1150lar <br /> 2. Determine rock layer width = 0.83 sqft/gpd x linear Loading Rate (LLR) <br /> 0.83 sqft/gpd x ) ). gpd/sqft = 10 ft Mound LLR <br /> 3. Length of rock layer = area _width = <br /> " L4)D sqft (D1) = 10 ft (D2) = / ft < 120 MPI <12 <br /> E. ROCK VOLUME > 120 MPI < 6 <br /> 1. Multiply rock area (D1) by rock depth of 1 ft <br /> to get cubic feet of rock <br /> 1-4I o sqft x 1 ft = 4i 0 cuft <br /> 2. Divide cuft by 27 cuft/cuyd to get cubic yards <br /> 410 cuft - 27 cuyd/cuft = 15 cuyd <br /> 3. Multiply cubic yards by 1.4 to get weight of rock in tons <br /> 15" cuyd x 1.4 ton/cuyd = Al tons <br /> D-33: Absorption Width Sizing Table <br /> F. SEWAGE ABSORPTION WIDTH Percolation Rate Loading Rate <br /> in Minutes per Soil Texture Gallons Absorption <br /> •Inch per day per Ratio <br /> (MPI) square foot <br /> Faster than 5 Coarse Sand 1.20 1.00 <br /> Medium Sand <br /> Absorption width equals absorption ratio (See Figure D-33) Loamy Sand <br /> Fine Sand <br /> 6 to IS .. • • 1 <br /> times rock layer width (D2) 16 to 30 Loam 0.60 2.00 <br /> 31 to 45 Silt Loam 0.50 2.40 <br /> 1 Silt <br /> 1 <br /> .LF/ x 1 o ft = 'J.Isp e r2 ft 46 to 60 Sandy Clay Lo, 1 2.67 <br /> Silty Clay Loam <br /> Cloy Loam <br /> 61 io 120 Silty Clay 0.24 5.00 <br /> Sandy Clay <br /> Clay <br /> ' Slower than 120• <br /> "5ynem designed for Jxse soils must be offer or r.erfomraoce <br /> J <br />