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<br />Armorlng Technlqu.. . <br /> <br />e <br /> <br />Sack Revetment - Sacks filled with sand or soil cement are typically used for emergency <br />flood control. however. they can be placed on the bank to deter erosion as well. Burlap <br />sacks are filled with selected material and are placed on the bank and allowed to <br />conform to the bank geometry for temporary control. Sacks can be filled with cement <br />mix. Which when wetted, can bond and form a concrete layer throughout the sack <br />revetment For this type of pennanent placement a recommended mixture of 15% <br />cement and 85% sand should be used. The sacks should be stepped one-half a bag and <br />lie horizontally along the stream bank. Holes or spaces should be included to equalize <br />hydrostatic pressure if the structure is to be penn anent. Figure 4-2 shows a typical <br />diagram of a sack revetment <br /> <br />FIGURE 4. 2 <br /> <br />Sack Revetment <br /> <br />Existing <br />BankJi <br /> <br /> <br />Sack Fill <br /> <br /> <br />IVon2H <br /> <br />1 <br /> <br />Varies <br /> <br /> <br />Varies <br /> <br />,<': <br />"'" . /' <br /> <br />N.W.S. 1 <br />W& <br /> <br />~ <br /> <br />.' <br /> <br />Only soil cement or sand cement filled sacks provide long-term protection if the <br />cements sets properly. Also, burlap sacks deteriorate after awhile. Costs for the sack <br />revetment are relatively high if labor costs are included, and may range from $150 to <br />$300 per linear foot of stream bank. Maintenance costs are estimated 10 be $15 to $25 <br />per year per foot, and the life span is limited. <br /> <br />Soil-Covered Riprap - On streams that carry a heavy suspended sediment load, riprap <br />banks will often become covered with sediment after the stream has experienced several <br />bankfull flows. Once a sufficient layer of silt has been deposited, nallD'aI vegetation <br />consisting of weeds and woody plants will become established quickly. In wban areas <br />or highly visible locations where it is advisable to keep banks mowed for aesthetic or <br />safety purposes, riprap may be covered with soil and seeded to accelerate this process or <br />done in areas where a cover of grass which can be moved is desired. Figure 4-3 shows a <br />typical diagram of soil covered riprap. <br /> <br />e <br /> <br />Benefits of covering riprap with soil and seeding grass are largely aesthetic. Although <br />access to the stream is improved, few aquatic or riparian habitat values are derived. <br />Edaphic and climatic conditions are the major constraints to covering riprap with soil <br />and seeding with vegetation, particularly grass. <br /> <br />Colorado Erosion Control Manual <br /> <br />29 <br />