sediment control function Silt fences, or temporary sediment control While a silt fence may be viewed as a filtering Silt fences are either pre-assembled (into a fences, often are the most visible form of device, it is probably better described as an ready-to-install unit) or assembled in the field. erosion or sediment control on a construction energy dissipater. It is a vertical permeable inter- Tractors with special attachments can slice a site. Used properly, silt fences can limit the ceptor designed to slow runoff and allow set- narrow trench in the soil and insert a fabric transport of eroded soil from disturbed areas. tling of soil particles from sediment-laden water. into the trench in a simultaneous operation. A silt fence is not an erosion control Even though the silt fence fabric (geotextile) The geotextile, posts, fastening method, device; it is a sediment control device. As does allow water passage while retaining most post spacing and reinforcement can be spec- soil particles become dislodged due to soil particles, the sediment actually settles out of ified using industry-accepted test methods. human activity, rain, wind and/or other the water before it reaches the fence. Silt fence installation procedures also are natural forces, they become sediment or A silt fence is intended for non-concentrated readily available. “silt.” Silt fences are designed to control water such as sheet flow. It is not intended for this sediment. concentrated flows of channels or swales.
environmental impact components and constructiondesign life and maintenance Sediment in stormwater is a pollutant. Silt fences have become popular over the last A silt fence should remain in place until Other pollutants such as fertilizers, pesti- 25 years. They typically consist of a geotextile sediment flow no longer exists or is being cides, oil and grease make stormwater fastened to wooden or metal posts. Support addressed by other means (i.e., new vegeta- runoff our most common cause of water metal wire or plastic mesh placed between tion). Design life could be a few months or pollution. In the United States, the the fabric and the posts provide reinforce- well over one year. Maintenance is essential Environmental Protection Agency has creat- ment in the event of heavy sediment loads. A for long-term performance, particularly ed the National Pollutant Discharge support rope, or tension cord, may be used at after storms. It may be necessary to “muck Elimination System. This permit program the top of the fence to straighten the posts out” heavy accumulations of sediment to controls water pollution by regulation point and strengthen the fence. The geotextile create capacity for additional sediment. sources that discharge pollutants in the height is commonly 2 to 3.5 feet; the post waters of the United States. Failure to com- height is commonly 3 to 5 feet. The geotextile ply with these regulations can result in work should be placed in a trench to prevent water stoppage and fines. flow from running under the fabric. for more summary information If appropriately specified, placed and main- To find out how tained, a silt fence can be an extremely geosynthetics can SiltSilt FenceFence effective sedimentation control device. It is a provide engineering viable tool that can be used in an effort to Geosynthetic Materials Association solutions, contact protect the environment using proper ero- the Geosynthetic Materials Association at 1801 sion and sediment control procedures. County Road B W.; Roseville, MN 55113-4061; ApplicationsApplications +(1) 651/225-6942; fax +(1) 651/631-9334; e- mail [email protected] or visit www.gmanow.com.
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