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• <br />11 <br />3. In minor shales or ditch lines where the maximum contributing <br />drainage area is no greater than 2 acres. <br />4. Where effectiveness is required for less than 3 months. <br />5. Under no circumstances should straw bale barriers be constructed in <br />live streams or in swales where there is the possibility of a <br />washout. <br />Planninq Considerations <br />Based on observations made in Virginia, Pennsylvania, Maryland, and other <br />parts of the nation, straw bale barriers have not been as effective as <br />many users had hoped they would be. There are three major reasons for <br />this. <br />Improper use of straw bale barriers has been a major problem. Straw bale <br />barriers have been used in streams and drainageways where high water <br />velocities and volumes have destroyed or impaired their effectiveness. <br />Improper placement and installation of the barriers, such as staking the <br />bales directly to the around with no soil seal or entrenchment, has <br />allowed undercutting and end flow. This has resulted in additions instead <br />of removal of sediment from runoff waters (Plate 1.05a). Finally, <br />inadequate maintenance lowers the effectiveness of these barriers. <br />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 <br />to lack of maintenance. <br />There are serious questions about the continued use of straw bale barriers <br />as they are presently installed and maintained." Averaging approximately <br />S1.00 per linear foot, the thousands of straw bale barriers used annually <br />in Florida represent sufficient expense that optimum installation <br />procedures should be emphasized. If such procedures are carefully <br />followed, straw bale barriers can be quite effective. <br />Design Criteria <br />A formal design is not required. <br />Construction Specifications <br />Sheet Flow Applications <br />I. Bales shall be placed in a single raw, lengthwise on the contour, <br />with ends of adjacent bales tightly abutting one another. <br />6i~ 309 <br />