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MOUND DESIGN PROCEDURE <br />(For Flows up to 1200 gptl) <br />A. Sewage Flow Rate <br />See D-7 or I-3, 4, or 5, or use <br />metered value; Flow Rate = <br />7-To gpd <br />B. Septic Tank Liquid Volume <br />(see C-3 or C-5) L; J,i gallons <br />C. Soil Characteristics <br />1. Depth to restricting layer <br />such as seasonally saturated <br />soil, bedrock, coarse soil, <br />etc.; 3 O inches <br />2. Depth of percolation tests; <br />/_inches <br />3. Number of percolation test <br />holes; holes <br />4. Ave. percolation rate; <br />25. 1 mp i <br />5. Landslope 7 1% or: <br />D. Rock Layer Dimensions' <br />1. Multiply gpd by 0.83 to <br />obtain required area of <br />rock layer; <br />Z, 'o gpd x 0. 83 =9'Z1.5_ sq f t <br />2. Select width of rock layer <br />(10 feet or less) - /O feet <br />3. Length of rock layer - Area <br />Width Q7,$sq ft to ft <br />- C2 3 ft <br />E. Rock Volume <br />1. Multiply rock area by rock depth <br />to get cubic feet of rock; <br />�11.5 sq ft xQ,75ft = V"cu ft <br />2. Divide cu ft by 27 cu ft/cu yd <br />to get cubic yards; 17.3 <br />3. Multiply cubic yards by 1.4 to <br />get weight of rock in tons; <br />/7.3 cu yds x 1.4 - 16/. 2 tons <br />E-19 <br />F. Pressure Distribution System <br />1. Select number of perforated <br />laterals 6 <br />2. Select perforation spacing <br />-3 ft <br />3. Select perforated lateral <br />length; Note if manifold is <br />at end of rock layer, lateral <br />length is rock layer length <br />less half a perforation <br />spacing. If manifold is in <br />center of rock layer, lateral <br />length is one-half rock layer <br />length less half c perforation <br />spacing. Perforated lateral <br />length = 29.7 ft. <br />4. Divide lateral length by perfor- <br />ation spacing to get number of <br />perforations per lateral <br />?/,Z feet 1. 3 feet = /Q perfs <br />Note: last perforation must be <br />in end cap, (see page E-14) <br />5. Multiply perforations per <br />lateral by number of laterals <br />to get total number of <br />perf itions; <br />/d perfs/lat x 4' lats n 60 <br />6. Determine required flow rate <br />by multiplying number of <br />perforations by flow per <br />perforation (see page E-17) <br />-perfs xQj7ygpin/perf = iff.ygpm <br />7. Select minimum required lateral <br />diameter from table on Page E-17; <br />cater table with perforation <br />spacing, perforation diameter, <br />and number of perforations per <br />lateral. Select minimum <br />diameter for perforated lateral <br />/Yy inches ute: 2 0" <br />G. Basal Width <br />1. Percolation rate in top 12 <br />inches of soil is ??:S&Lmpi <br />2. Select allowable soil loading <br />rate from table on page E-16; <br />&I 0, Y5gpd /f t2 <br />