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Chapter 4 - Best Management Practices for Erosion and Sediment Control r 7. When extra strength filter fabric and closer post spacing are used , the wire mesh support fence may be eliminated. In such a case , the filter fabric is stapled or "■ wired directly to the posts with all other provisions of item No . 6 applying . 8 . When attaching two silt, fenIces together, place the end post of the second fence inside the end post of the first fence. Rotate both posts at least 180 degrees on a clockwise directlori to create a tight seat with the filter fabric. Drive both pasts_ into +r. the ground and bury the flap. (See Plate 4 .06g) 9 , The french shall be - backfilled and the soil compacted over the filter fabric . 10 . The most effective application consists of 'a double row of silt fences spaced a minimum of three feet apart. The._ three foot :separation is so that if the first row collapses it will not fall on the second row. - Wire 'or. synthetic mesh is may be used Ow to reinforce the first row. (See Plate 4.06c) 11 . When used to , control sediments from a steep slope , sill ferices should. be placed Om away from the toe of the slope for increased holding capacity. ' (See Plate 4 . 06f) 12. Silt fences shall be removed when they have served their useful purpose , but not before the upslope area has been permanently stabilized . i Channel Flow Applications 1 . If a filter barrier is to be constructed across a ditch line or swale ; the barrier shall of sufficient .length such that the bottom of the end sections of fence are higher in elevation than the top of the center section to eliminate end flow. : The pian configuration shall resemble an arc or horseshoe with the ends oriented upslope. (See Plate 4 .06b) . 2. Use FDOT Standard Index 102 , Chart 1 (Plate 4.06a) as a guide for spacing . 41 3 . The remaining steps for installing a filter barrier for sheet flow applications apply here. Maintenance 1 . Silt fences and filter barriers shall be inspected immediately after each rainfall and at least daily during prolonged rainfall. Any required repairs shall be made immediately. 2 . Should the fabric on a silt fence or filter barrier decompose or become ineffective before the end of the expected usable life and the barrier still be necessary, the fabric shall be replaced promptly. 3. Sediment deposits should be removed after each storm event. They must be removed when deposits reach approximately. one-half the height of the barrier. 4-27