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In this particular example the number of acres per constructed check dam is 7.54. This value is an <br />interpolation of known non-linear values generated by the SEDCAD models, Table 4.8-5a. The capacity <br />of each check dam at an 8% slope based on typical construction is found to be 0.031 ac -ft, Table 4.8-5a. <br />By simply dividing the total watershed acreage by the above acres per check dam gives the number of <br />required check dams. In this case, 40.58 check dams are needed, rounded up to 41. <br />Total water storage needed for this drainage is then calculated by multiplying the number of check dams <br />required by the capacity of each check dam for the specified drainage slope of 8%. <br />[1.26 ac -ft (total storage needed) = 40.58 (number of check dams required) * 0.031 ac -ft (capacity <br />of single check dam)] <br />If dozer basins are used in conjunction with check dams, the as -built storage capacity of the dozer basins <br />in the drainage will be subtracted from the total storage needed and re -solved for the required number of <br />check dams. <br />For example, if it is found that the cumulative as -built capacity of dozer basins in this particular drainage is <br />0.50 acre feet, we re -solve for the number of check dams. <br />[1.26 ac -ft (total storage needed) — 0.50 ac -ft (capacity detained by constructed dozer basins) _ <br />0.76 ac -ft (volume required to be detained by check dams)] <br />The reduced number of check dams is found as follows. <br />[0.76 ac -ft (volume required to be detained by check dams) = x (number of check dams required) <br />* 0.031 ac -ft (capacity of single check dam)] <br />Solving for x, the new required number of check dams is 24.51, rounded up to 25. <br />Using this procedure the required amount of storage capacity for a drainage design can be calculated and <br />executed through the use of check dams and dozer basins. Structures will be built as needed per the <br />recommendations of the calculations and field placed as appropriate to maximize drainage channel <br />stability. <br />4-183m <br />Revision: "- G 7 <br />APR 012015 Approved: <br />