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Chapter 4 - Best Management Practices for Erosion and Sediment Control <br /> a 4, 05 STRAW BALE BARRIER <br /> ( ES BMP 1 , 05) <br /> a Definition <br /> A temporary sediment barrier consisting of a row of entrenched and anchored straw bales. <br /> a <br /> Purposes <br /> a 1 . To intercept and detain small amounts of sediment from disturbed areas of limited <br /> extent. <br /> a 2 . To decrease the velocity of sheet flows and low-to-moderate level channel flows . <br /> Conditions Where Practice Applies <br /> 1 . Below disturbed areas subject to sheet and rill erosion . <br /> a 2 . Where the size of the drainage area is no greater than 1 /4 acre per 100 feet ( 1 .3 <br /> ha/100 m) of barrier length ; the maximum slope length behind the barrier is 100 feet <br /> (30 m) ; and the maximum slope gradient behind the barrier is 50 percent (2: 1 ) . <br /> a <br /> 3 . In minor swales or ditch lines where the maximum contributing drainage area is no <br /> greater than 2 acres(0 . 8 ha) . <br /> a <br /> 4 . Where effectiveness is required for less than 3 months . <br /> a 5 . Under no circumstances should straw bale barriers be constructed in streams or in <br /> swales where there is a possibility of a washout. <br /> a Planninn Considerations <br /> Improper use of straw bale barriers has been a major problem . Straw bale barriers have <br /> a been used in streams and drainageways where high water velocities and volumes have <br /> destroyed or impaired their effectiveness . Improper placement and installation of the <br /> barriers , such as staking the bales directly to the ground with no soil seal or entrenchment, <br /> a has allowed undercutting and end flow. This has resulted in additions instead of removal <br /> of sediment from runoff waters. Finally, inadequate maintenance lowers the effectiveness <br /> of these barriers . Trapping efficiencies of carefully installed straw bale barriers on one <br />�. project in Virginia dropped from 57 percent to 16 percent in one month due to lack of <br /> maintenance . <br /> There are serious questions about the continued use of straw bale barriers as they are <br /> presently installed and maintained . Averaging approximately $3 to $6 per linear foot <br /> installed ($ 10 to $20 / m) the thousands of straw bale barriers used annually in Florida <br /> a represent sufficient expense that optimum installation procedures should be emphasized . <br /> If such procedures are carefully followed , straw bale barriers can be quite effective . <br /> a 4- 13 <br /> a <br />