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.' MOUND DESIGN WORK SHEET(For Flows up to 1200 d) <br /> A. Average Design FLOW A-1: Estimated Sewage Flows in Gallons per Day <br /> number o <br /> Estimated 4 S0 gpd (see figure A-1) bedrooms Class I clan II class III 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 /> oZ —/00 0allons (see $ure C-1) 7 1050 600 370 II,or III <br /> $ 8 1 1200 1 675 1 408 1 columns. <br /> C. SOILS (refer to site evaluation) Gl: Septic A capacities auons <br /> Number of Minimum li9 uid d l with U uid capacity <br /> 1. Depth to restricting layer= a•0 ¢ a•3 feet <br /> Bedrooms Capacity B�age&po wit disc& <br /> 2. Depth of percolation tests = 40 feet 2aless 750 1125 1500 <br /> 3. Texture 61-�A`A L-0�4wN 3 as wo 2WS a 6 115M 500 2250 3000 <br /> Percolation rate -4.4 mpi 7,8 or 9 2000 30°0 <br /> 4. Soil loading rate t 4.,' gpd/sqft(see figure D-33) <br /> 5. Percent land slope 3 % <br /> D. ROCK LAYER DIMENSIONS <br /> 1. Multiply average design flow (A) by 0.83 to obtain required rock layer area. <br /> gpd x 0.83 sqft/gpd = 3 7 3 sgft+o'5,;=410'6 <br /> 2. Determine rock layer width= 0.83 sqft/gpd x linear Loading Rate (LLR) <br /> 0.83 sqft/gpd x 1-2_ gpd/sgft= 10 ft Mound LLR <br /> 3. Length of rock layer = area+width= <br /> H 10 sqft(D1) + /0 ft (D2) =4_ft < 120 MPI <12 <br /> E. ROCK VOLUME > 120 MPI < 6 . <br /> 1. Multiply rock area (Dl)by rock depth of 1 ft to get cubic feet of rock <br /> L4) o sgft x 1 ft = LhQ cult <br /> 2. Divide cuft by 27 cuft/cuyd to get cubic yards <br /> 4) 0 cuft +27 cuyd/cuft=1S-cuyd <br /> 3. Multiply cubic yards by 1.4 to get weight of rock in tons <br /> 1 S cuyd x 1.4 ton/cuyd =a)_tons <br /> 'D-33: Absorption Width Sizing Table <br /> Percolation Rate Loading Rate <br /> F. SEWAGE ABSORPTION WIDTH in Minutes per Soil Texture Gallana Absorption <br /> Inch per day per Ratio <br /> MPI foot <br /> Faster than 3 Coarse Sand 1.20 1.00 <br /> Medium Sand <br /> Absorption width equals absorption ratio (See Figure D-33) Loamy ;:d n79 I <br /> times rock layer width (D2) t o, o0 <br /> l teaSi t .a0 <br /> 2,v? x�ft =�ft Sill <br /> 46to60 Silt Q0 Loam 0.45 2.67 <br /> 61 to 120 Siltq Clay 0.24 .00 <br /> Sandy pay <br /> i Clay <br /> Slower than 120*1 <br /> •Symm designed for awe soils mm be other or perfomence <br />