Properly installed silt fence is the most effective temporary sediment control device available

1. Properly installed silt fence is the most effective temporary sediment control device available 100 ft. of effective silt fence can retain 180 tons of sediment.

2. Properly installed silt fence detains water for sedimentation to occur

3. Sediment control devices primarily collect larger particles of soil because clays and silts are very small. Large particles cause further erosion – thus a multiplying effect - once introduced into a stream.

4. Goal of silt fence • Silt fence, for maximum efficacy, should detain water for sedimentation to occur. • Occasionally it may be used to divert stormwater to a storage area. • Silt fence, at a minimum, should retain large soil particles and prevent loss from the site.

5. Two most common problems • Placement issues – won’t pond water or insufficient quantity for the area • Installation issues - inadequate backfill and/or compaction – one weak area allows the fence to fail

6. Placement Installation Support Effective silt fence works like a chain… Each link must work; if one link fails, the system fails Quantity Compaction Attachment

7. A failure on any segmentof the system makes theentire silt fence a completewaste of money!

8. PLACEMENTrefers to specific locations on each construction site, and to specific designs (layouts) at each location.

9. The ends of a “smile” must always be long enough to pond water and sediment.

10. Designs called J-hooks insure water & sediment pond behind each silt fence.

11. Silt Fence Placement Correct Incorrect

12. Correct Silt Fence Placement

13. Incorrect Silt Fence Placement

14. Streets that have been excavated,but not paved, are prime areas for sediment discharge. Recommendsilt fence to control sediment and velocity.

15. Silt fence should pond water to be considered effective.

16. Myth – flat sites do not need protection

17. Stop sediment before it reaches the pavement. stormwater inlet

18. Ditch checks • Do not install silt fence in a continuous flow situation, or on the discharge of an outlet. • Install on the inlet side of a culvert. • A properly installed, compacted, and supported silt fence will retain significant sediment in a ditch situation. • Shallow posting (wood posts?) and poor compaction will not be effective.

19. 25 tons of sediment captured per fence in a ditch situation

20. Concentrated flow is standard on many SWPP’s.

21. Proper installation can withstand concentrated flows

22. Leave room for sediment storage at toe of slope

23. Protect area intakes with larger silt fence structures, if possible

24. Proper placement should insure sedimentation.

25. On-site adjustment is mandatory • Grading plans and PPP’s are often drawn in an office many months prior to disturbance. • The ESC contractor must adjust the plan to properly control the site, or at a minimum notify the site managers of potential problems.

26. Do not use silt fence: • Where you can not create a storage area for runoff, such as on steep slopes, on small areas, or in short segments. • Where you can not prevent water running around the end • In a V-shaped or shallow channel

27. Placement Installation Support Effective silt fence works like a chain… Each link must work; if one link fails, the system fails Quantity Compaction Attachment

28. QUANTITY relates to area of control. The volume of water from a large site can not be controlled in one run of silt fence. Multiple locations or storage areas are often required.

29. Large areas often need additional runs installed in the interior to reduce the volume of water reaching the perimeter fences.

30. Long runs should be avoided. They tend to accumulate sediment in one area, causing premature overflow.

31. Long runs often concentrate water and then overflow

32. Breaking up a run more than doubles storage area

33. Multiple runs slow runoff velocity and add storage area on site.

34. Proper Quantity 100 ft. of silt fence per 10,000 sq. ft.of disturbed area seems to be an adequate rule of thumb for sediment control and economics.

35. Placement Installation Support Effective silt fence works like a chain… Each link must work; if one link fails, the system fails Quantity Compaction Attachment

36. INSTALLATION relates to how the fabric is placed in the soil, appropriate depth of placement, and appropriate backfill for an effective silt fence.

37. Improper installation often leaves silt fence blowing in the wind.

40. No compaction = washouts

41. DOT job with inspector does not insure proper installation.

42. Mechanical installation reduces many labor-related installation problems.

43. Mechanical installation provides consistent, dependable silt fence.

44. The slicing method disturbs, but does not excavate soil, creating an optimal condition for compaction.

45. Placement Installation Support Effective silt fence works like a chain… Each link must work; if one link fails, the system fails Quantity Compaction Attachment

46. COMPACTION relates to soil permeability. Loose or trash-filled backfill is easily saturated with water and washed out under the silt fence. Compacted soil resists saturation, and thus washouts.

47. Silt Fence Study

48. EPA co-sponsored research has shown compaction is the critical factor in silt fence effectiveness. • Trenches must be over-backfilled and mechanically compacted – BEFORE installing posts • Slicing installation must be mechanically compacted before installing posts

50. Poor compaction means washouts