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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 of <br /> Estimated O gpd (see figure A-1) bedrooms Class I Class 11 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 1, <br /> a - ►a S v gallons (see figure C-1) 7 1050 600 370 ll, or ul <br /> T,amT c N �rtg .. 8 1200 675 408 columns. <br /> C. SOILS (refer to site evaluation) C-1: Septic Tank Ca acities(in allons <br /> Liquid capacity <br /> Number of Minimum Liquid Liquid capacity with with disposal& <br /> 1. Depth to restricting layer = 'A,ta, R R.Ofeet Bedrooms Capacity garbage disposal lift inside <br /> 2. Depth of percolation tests = ).0 feet 2orless 750 1125 1500 <br /> 3. Texture Lo A vvl S orb 1500 150 2000 <br /> Percolation rate 44."5 mpi 7,s or 9 2000 3000 3000 <br /> 4. Soil loading rate ,4 ��' gpd/sqft (see figure D-33) <br /> 5. Percent land slope 5 % <br /> D. ROCK LAYER DIMENSIONS <br /> 1. Multiply average design flow (A) by 0.83 to obtain required rock layer area. <br /> SD gpd x 0.83 sgft/gpd = (,a sgft <br /> 2. Determine rock layer width = 0.83 sqft/gpd x linear Loading Rate (LLR <br /> 0.83 sqft/gpd x )a gpd/sqft = /o ft Mound LLR <br /> 3. Length of rock layer = area _ width = <br /> c sgft (D1) •. Ick ft (D2) = to a., ft < 120 MPI < 1 2 <br /> to k ay +aqua a�tuo — <br /> E. ROCK VOLUME > 120 MPI < 6 <br /> 1. Multiply rock area (D1) by rock depth of 1 ft to get cubic feet of rock <br /> u90 0 sgft x 1 ft = �t-1 o cuft <br /> 2. Divide cuft by 27 cult/cuyd to get cubic yards <br /> cuft - 27 cuyd/cuft = C-) cuyd <br /> 3. Multiply cubic yards by 1.4 to get weight of rock in tons <br /> cuyd x 1.4 ton/cuyd = 1 '2 tons <br /> D-33: Absorption Width Sizing Table <br /> IF. SEWAGE ABSORPTION WIDTH in`Mianon Rate Loading Rate <br /> n Minuses 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) Fn yaand <br /> nd <br /> 0.79 1 so <br /> times rock layer width (D2) 40 <br /> 3I to 405 <br /> Sill°laoem 0:0 2:0 <br /> 4 x /0 ft = U ft 46 to 60 Sill <br /> Sandy Clay Lo 0.45 2.67 <br /> Silty Clay Loam <br /> 61 io 120 Silty Clay 0.24 5.00 <br /> Sandy Clay <br /> Clay <br /> Slower than 120` <br /> -System designed for these soils must be other or performeoce <br />