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• <br /> 77414/ "ttiovE/1-, <br /> • <br /> / S 6 E-19 <br /> MOUND DESIGN PROCEDURE <br /> (For Flows up to 1200 gpd) <br /> • <br /> A. Sewage Flow Rate F. Pre'ssu`re Distribution System <br /> See D-7 or I-3, 4, or 5, or use <br /> metered value; Flow Rate = 1. Select number of perforated ' <br /> 75a gpd laterals <br /> 2. Select perforation spacing <br /> B. Septic Tank Liquid Volume L. 3 ft <br /> (see C-3 or C-5) /23-0 gallons <br /> I COp „ 3. Select perforated lateral <br /> C. Soil Characteristics length; Note if manifold is <br /> at end of rock layer, lateral <br /> 1. Depth to restricting layer leng hi .rock layer length <br /> such as seasonally saturated less half a- perforation <br /> soil, bedrock, coarse soil, spacing. .If manifold is in <br /> etc. ; 7 ff inches center of rock layer, lateral <br /> 2. Depth of percolation tests; length is one-i�alf rock layer <br /> /5 inches length less half a perforation • <br /> spacing. Perforated lateral. <br /> 3. Number of percolation test length = 29. 7 ft. <br /> holes; ,3 holes <br /> 4. Divide lateral length by perfor- <br /> 4. Ave. percolation rate; ation spacing to get number of <br /> 53- S mpi perforations per lateral <br /> 5. Landslope = / % 91,2 feet = 3 feet = /0 perfs <br /> Note: last perforation must be <br /> D. Rock Layer Dimensions ' in end cap, (see page E-14) <br /> 1. Multiply gpd by 0.83 to 5. Multiply perforations per <br /> lateral.. by number of laterals <br /> obtain required area of <br /> rock layer; to get total number• of <br /> . 750 gpd x 0.83 =(21.S sq ft perforations; <br /> /0 perfs/lat x lats = (0 <br /> 2. Select width of rock layer <br /> (10 feet or less) _ /0 feet 6. Determine required flow rate <br /> by multiplying number of <br /> 3. Length of rock layer = Area perforations by flow per <br /> Widtha2,5sq ft /p fterforation <br /> P (see page E-17) <br /> 0. 3 ft GO..p .r.f.s. •x0.7ygpm/perf = 5eV.Ygpm <br /> • <br /> E. Rock Volume 7. Select minimum required lateral <br /> diameter from table on Page .E-17; <br /> 1. Multiply rock area by rock depth enter table with perforation <br /> to get cubic feet of rock; spacing, perforation diameter, <br /> (22.5 sq ft xO. 75ft = W7 cu ft and number of perforations per <br /> 2. Divide cu ft by 27 cu ft/cu yd lateral. Select minimum <br /> • diameter for perforated lateral <br /> t- get cubic yards; /13 = <br /> 3. .Multiply cubic yards by 1.4 to ///,,, inches uta. �� <br /> Z <br /> get weight of rock in tons; G. Basal Width <br /> /7.3 cu yds x 1.4 7 .24/.. 2 tons 1. Percolation rate in top 12 <br /> inches of soil is SY $ mpi • <br /> • <br /> 2. Select allowable soil loading <br /> rate from table on page E-16; <br /> • C�. VSgpd/ft2 <br />