Silt FenceSilt Barrier, Silt Curtain, Floating Silt Curtain, Silt Protector
Silt fence is used as a temporary perimeter erosion prevention & control device around sites where there will be a soil disturbance due to construction and land clearing activities.They are normally manufactured from woven geotextile filter fabric attached to wooden stakes spaced at regular intervals along the site perimeter. The filter fabric should be entrenched in the ground between the support stakes. When installed correctly and inspected frequently, they can be an economical effective barrier to sediment leaving the site.
On occasion you will need staked silt barrier to control sheet flow, or floating silt curtain if your project is in, on or next to a water resource.
Specification
Silt fence is generally used on construction sites with relatively small drainage areas. They are appropriate in areas where runoff will be low-level shallow flow, not to exceed 0.5 cfs. The drainage area required for there use generally should not exceed 1/4 acre per 100-foot of fence length. Slope length above the fence should not exceed 100 feet (NAHB, 1995) as this can have a negative impact on performance. Design Considerations: Fabrics used for silt fences should be a previous sheets of geotextile material such as polypropylene, nylon or polyester. These are chosen based on minimum synthetic fabric requirements, as shown below.
2) Tensile Strength at 20 % (maximum) should allow for Standard Strength of 30 lbs/linear inch (minimum) 3) Elongation effects should consider Extra Strength of 50 lbs/linear inch (minimum) 4) Ultraviolet Radiation allowance of 90 % (minimum) 5) Slurry Flow Rate should be 0.3 gal/ft2/min (minimum) Requirements vary a great deal and good way to find out more is by contacting a local regulatory agency or a Certified Erosion Control Professional.
Inspection should be done frequently, as well as after each rainfall event, to ensure that they are intact. If gaps or tears are found, they should be repaired or the fabric should be replaced immediately. Accumulated sediments should be removed from the fence base when the sediment reaches one-third to one-half the height of the fence to avoid failure. Sediment removal should occur more frequently if accumulated sediment is creating noticeable strain on the fabric. When the silt fence is removed, the accumulated sediment also should be removed.
USEPA (1993) reports the following effectiveness ranges for silt fences constructed of filter fabric that are properly installed and well maintained: Average total suspended solids removal of 70 percent, sand removal of 80 to 90 percent, silt-loam removal of 50 to 80 percent, and silt-clay-loam removal of 0 to 20 percent. Removal rates are highly dependent on local conditions and installation.
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