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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I. <br /> <br />The major drainageways will require <br /> <br />either riprap or paving where they pass through the studied part <br /> <br />of the basin, The sides of the main Cottonwood Creek channel should <br /> <br />be improved by use of either riprap, gabions or concrete paving. <br /> <br />The riprap or gabion system is preferable on this stream, provided <br /> <br />that the size of riprap is large enough to resist the full flood <br /> <br />tractive forces. The average weight of riprap pieces should be not <br /> <br />less than 350 pounds. The bottom of this channel should remain as <br /> <br />earth. <br /> <br />The subsurface moisture conditions <br /> <br />along the main channel of south Sub-basin 23 dictate that this <br /> <br />drainageway should be fully lined or placed in an underground <br /> <br />system. In some areas a subdrainage lateral system should also be <br /> <br />used for proper development of the load, In general, concrete <br /> <br />paving with appropriate velocity reduction steps is the preferable <br /> <br />system, <br /> <br />All bridges and concrete boxes along <br /> <br />drainageways must have intake and outlet paved adjacent channels <br /> <br />and scour protection lips at points which use earth bottom channels, <br /> <br />Since a few ditches may be in easements from necessity, precautions <br /> <br />against placing fences across the ditches are required, Placing <br /> <br />any fence, particularly o~ the chainlink variety, across a drainage- <br /> <br />way is a dangerous practice, cannot be recommended and should not <br /> <br />be allowed. <br /> <br />All proposed bridges and concrete <br /> <br />boxes over major drainageways should be designed to carry the <br /> <br />-27- <br />