subject: Using A Silt Fence In A Construction Area [print this page] Using a silt fence when doing construction near waterways, streams, lakes, or rivers is not only a good idea, it is sometimes a requirement. The fence is a temporary structure but it keeps the dirt that is being excavated around the site from being washed into the nearby water, thus preventing contamination and filling up of streams and ditch lines that feed our lakes and ponds.
In order to work properly your fence must be placed in the downhill area of your site so the run off will travel to it for filtering. Bowl or smile shaping of the fencing will work much better than a long straight line. Cupped, segmented arrangements funnel the water into place while whole straight lines are prone to flooding and washout. The sediment will just flow over the top.
Keep in mind that if your site is a large one, you will need to put in more than one segment of the system. Even one inch of rain on a construction site can produce a great run off. So one length of barrier may not be enough. The segments should all be less than 200 feet long. One hundred feet of fencing to ten thousand square feet of excavation is a good guide to remember.
The bottom edging of your fabric needs to be buried in the soil so that the water doesn't run underneath it. Mechanical installation is the recommended way of installing the system, as it does not dig up the area in the way that trenching does. And mechanical installation does not disrupt the soil like hand trenching does.
As your system is installed, you will have an uphill side and a downhill side. The uphill side is where the water is going to hit your barrier. Because of the pressure that will be applied here, the soil must be compacted so that it will hold the fabric in place. This is another reason to install mechanically. Hand trenching loosens the soil, creating more work and less efficiency. A machine that is specially created for the fencing job is much more efficient.
Your barrier will have to be attached to posts. Wood post are acceptable but steel does a much better job and they last longer. Posts should go into the ground as far as your fabric is deep. So if the membrane is thirty six inches high, your posts need to go into the ground thirty six inches, also.
The distance between your posts is also important to the success of your system. High stress areas need stakes that are closer together (4-5 feet apart). While portions expected to experience lower pressure can work with posts as much as 7 feet apart.
The use of a silt fence in any construction area is crucial to keeping the topsoil in place and preventing pollution to our lakes and streams. Proper installation and arrangement will insure success of the system.
