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design for these locations will need to include the gradation <br />specification, thickness of the riprap layer, and appropriate <br />gravel filter blanket and/or filter cloth underliner. The riprap <br />should extend up 1.he channel banks to a height above the maximum <br />depth of flow. "Typical" design cross sections should be provided, <br />as appropriate. <br />4. Amended page IV-24 states that ditches which are not riprapped <br />or gravel surfaced, along with exposed cut or fill slopes <br />associated with ponds, access roads, etc., will be heavily mulched <br />and seeded upon ~~ompletion of construction. "Erosion control <br />measures such as fiber blankets will be utilized as required to <br />control erosion until the vegetation process is completed." <br />With the exception of certain ditch segments to be specifically <br />identified as discussed above, all perimeter ditches which are not <br />riprapped, as well as adjacent disturbances such as buffer strips, <br />berms, etc., wi1:1 need to be seeded and mulched this fall. <br />Specifications for the fiber blanket product to be used in the <br />ditches will need~to be provided in the application, along with the <br />seedmix to be used. There does not appear to be a seedmix <br />specifically for grass lined channels in the permit application, <br />although the gra:>s component of the cut and fill slope mix <br />specified on pag~a V-42 would appear to be appropriate, with <br />modifications. The specified variety of western wheatgrass in this <br />mix is listed as "Amur"; it should be "Rosana". There is no such <br />grass as "green needle-and-thread"; this should be green <br />needlegrass, (Stipa viridula). Also, the broadcast seeding rate <br />of 30 PLS seeds per square foot is too low. A rate of 80 to 100 <br />PLS per square foot is recommended. A specific seedmix for grass <br />lined channels should be included in the application. Seeded <br />disturbances adjacent to the ditches should be straw mulched as <br />specified in the permit. <br />5. Amended page IV-24 contains the statement that "ditches will <br />be seeded and energy dissipation devices such as cobble dams will <br />be utilized in ditches on steep slopes where water velocity is <br />expected to exceed four feet per second and may cause erosion <br />problems." Cobble check dams have been installed in various <br />locations at spacings indicated on Map 77 and Map 77A on RP-4 and <br />RP-5. Cobble check dams have not been used on RP-2/3 ditches, <br />although they may be warranted in certain locations such as upper <br />segments of the east side perimeter ditch. <br />Apparently, the application contains no specific design for the <br />cobble dams. As noted in the inspection report, the dams consist <br />of piles of the 4" river rock at regular intervals. In some <br />locations, the rock has been piled too high in the ditch, such that <br />the design capacity of the ditch has been reduced at the check dam <br />locations. A specific design for the cobble dams will need to be <br />4 <br />