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<br />- <br /> <br />DISADVANTAGES: 1) Stab; I ity of rlprap blanket is hard to accompilsh. <br /> <br />2) Materljls may be hard to obtain. <br /> <br />3) Heavy 3Quipment required for construction. <br /> <br />4) Difficult to construct where access is limited. <br /> <br />5) Moderahely high initial costs. <br /> <br />COSTS:..!! In-place costs of a riprap blanket <br />and transportation of stone are ~23/cubic <br />bank-foot, tota t cost wou I cI equate to $35 per <br /> <br />including <br />yardS <br />bank-foot <br /> <br />bank preparation, bedding material <br />Assuming 1-1/2 cubic yards per <br />of protection. <br /> <br />MAINTENANCE REQUIREMENTS: This structure Is subject to displacement. The effectiveness <br />of the structure wi II be impaired by thinning of the protective layer or settl ing of the <br />structure. Restoration cf the rock slope protection to the designed top elevation, <br />equivalent thickness, and reduction of voids in the facing should be aecampl ished when <br />needed. <br /> <br />ENV I RONMENTAL ASPECT: No specia I equ i pment or construct ion pract ices are necessary for <br />r i prap protect ion. Th is cspect lessens the Impacts associ ated with construct Ion on the <br />riverine ecosystem. The reck structure, although difficult to walk on, takes on a natural <br />appearance, and is acceptable in recreational areas. If riprap is exposed to freshwater, <br />vegetation wi I I often grow through rocks~ adding structural value to the bank material and <br />restoring plants which can be used by wildlife. Rlprap In an aquatic environment allows <br />for attachment sites for organisms providing a food source and habitat for fish. A <br />negative aspect of riprap is the extensive bank reShaping sometimes associated with Its <br />placement. Removal of vegEltation in preparation for rlprapping can destroy native plants <br />and wi Idllfe habitat and t3ke on a channelized appearance which may not be aesthetically <br />pleasing. Manual placemen't of rlprap may prove to be less environmentally damaging and <br />give the protected area a TOre natura I appearance. Vegetat ion shou I d be a II owed to grow <br />through the riprap. Riprap blankets appear to be the most suitable type of bank structure <br />for roost locations from an overall viewpoint that takes cost-effectiveness and <br />environmental impacts, as w311 as degree of protection, into account. <br /> <br />..!! Estimated costs incl Jded in this brochure assume protection of a 12-foot high <br />streambank. <br /> <br />Y Costs shown are $23 per cub i c yard. Depend i ng on construct Ion methods, actua I cost <br />may vary by plus or minus 21) percent of values presented in this brochure. <br /> <br />12 <br />