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E-20 <br />MOUND DESIGN PROCEDURE (Continued) <br />(For Flows up to 1200 gpd) <br />G.3. Calculate basal width ratio <br />by dividing rock layer <br />loading rate of 1.20 gpd/ft2 <br />by allowable soil loading <br />rate; <br />1.20 gpd/f t2 = 0.60gpd/f t2 = I. 0 <br />Check this value on page E-16. <br />4. Multiply basal width ratio by <br />rock layer width to get <br />required basal width; <br />Z.0 x _of t= 20 f t <br />H. Downslope Dike Width <br />1. If landslope is 3% or more, <br />subtract rock layer width <br />from basal width to obtain <br />minimum downslope dike toe width <br />20 ft- /O ft = _oft <br />2. Calculate mound height at edge <br />of rock layer on downslope side; <br />a. Determine depth of clean sand <br />fill at upslope edge of rock <br />layer: / feet <br />b. Multiply rock layer width by <br />landslope to determine drop <br />in elevation; <br />/0 x % 100 =0.`i ft <br />c. Add drop in elevation to depth <br />of clean sand at upslope edge <br />of rock layer to get depth of <br />clean sand at downslope edge <br />of rock layer. <br />O.y ft + / ft a /.y ft <br />d. Add depth of clean sand at down - <br />slope edge to depth of rock <br />layer to depth of soil backfill <br />to get mound height at downslope <br />edge of rock layer; <br />/.Vft +Q,75ft +/.Zsft - -?.yft <br />e. Enter table on page E-18 with <br />landslope and downslope dike <br />ratio. Select dike multiplier <br />of .?. S/ / 3: / lYOo"f <br />H.2.f. Multiply dike multiplier by <br />downslope mound height to get <br />downslope dike width; <br />-7.VI x .7.1/ = 1/ 6'ft <br />g. Compare the values of step 11.1 <br />and step 11.2.f. Select the <br />greater of the two values as <br />the downslope dike width; <br />//. 6 feet <br />h. Calculate upslope dike width <br />using upslope mound height <br />and upslope dike multiplier <br />trom pages E-18; y 0 f t <br />i. Total mound width is the sum <br />of upslope dike width plus rock <br />layer width plus downslope dike <br />width; <br />80ft + /0 ft +//6ft =?9.Cft <br />3. If landslope is 2.9 percent or <br />less, basal width includes both <br />the upslope and do:nslope dike <br />widths. <br />a. Calculate downslope dike: width <br />using steps N.2.a. through <br />11.2.f; feet <br />b. Calculate upslope dike width <br />using upslope mound height and <br />dike multiplier from Pale E-18; <br />x ft = ft <br />c. Add downslope dike width to <br />upslope dike width to rock <br />layer width to get total mound <br />width; <br />ft + ft + ft ft <br />d. Compare total mound width to <br />required basal width from step <br />G.4. If total mound width is <br />greater than required basal <br />width, use calculated dike <br />widths. If required basal <br />width is greater than total <br />mound width, increase downslopo <br />dike width. <br />