Amount of added ultraviolet inhibitors
You may have heard about silt fences, filter fences, straw bale or brush fences. These types of fences represent types of sediment barriers which offer erosion protection during a construction. They are temporary structures which prevent the flowing of sediment runoffs.
- Silt fences
They provide amounts of sediment retention, depending on the materials with which they’re made. Wooven materials remain strong enough so as not to require a wire mesh for support and they filter more efficiently than the unwoven synthetic fabrics.
The fabric material is supported by wooden posts or metal posts.
Silt fences have a life span of about 6 months, but this depends on the amount of added ultraviolet inhibitors; are recommended for sloped areas located near ponds and around storm drains.
They are the most expensive in their category.
- Filter fences
This type of silt fence has the role of slowing down the flow of sediment more efficiently than the other categories, having an average life span of about 3 months.
They consist of burlap or synthetic filter fabric and can be wired to steel or stapled to wooden stakes, being relatively inexpensive.
Filter fences are most likely to be found near storm drains or stream channels( with a runoff less than 1 cubic foot/second).
- Straw bales & brush fence barriers
These types of sediment barriers offer a limited retention in the smaller drainage areas.
Straw bales, which are minimum 50 pounds each, reduce erosion and improve water quality when placed below the disturbed area.
Brush windows( cut or compressed) can either be wrapped with fabric, staked on the downhill side or secured with stakes on alternate sides.
The average life span of these 2 types of fences is 3 months, but they should only be used in areas where no other materials are available.