Top 5 Tips for Choosing and Installing An Effective Silt Fence

Our waterways need protection now more than ever. Many agencies, DOTs, and more are continually using silt fencing as a last ditch effort to keep sediment and stormwater from leaving construction sites and entering local waterways. A great need has also risen to provide additional protection in wetlands and other natural areas where wildlife sensitivity is at an extreme.

Silt fencing provides agencies with a simple, but very effective tool to stop the movement of sediments into waterways. Unwanted sediment runoff often contaminates nearby waterways and erodes terrain when construction work disturbs the soil, which is why silt fence fabric has become a staple in the construction industry.

Another area where silt fencing is starting to gain traction is on wind and solar farm projects. These types of sites are very often rural farmland, making it extremely important to manage sediment runoff and keep it out of the local waterways.

Falling under the geotextiles category, silt fencing is commonly used in these applications to prevent erosion by trapping sediment and preventing excessive runoff. It provides a low cost, easy to maintain way to protect the surrounding environment. The fabrics used for standard staked silt fences fall under three grade-categories, namely economy grade, contractor grade, and DOT grade. These fabrics offer good filtration capabilities, and are able to contain dirt, sediment, and other displaced materials while allowing water to flow through, effectively limiting erosion.

Choosing and Installing An Effective Silt Fence

Silt fences that are improperly installed are very often ineffective. Below are tips for choosing the right type of silt fencing for the job, and how to properly install it.

Height

The slope of the project site will determine what height the silt fencing needs to be. A 16-inch height should be effective on a generally flat site, meaning one that has less than a six percent slope. When the slope increases, taller silt fencing is required. There is a limit, however, to how tall a fence should be. You should never exceed 28-inches because this introduces the threat of flooding below the fence if it should fail. The right height of silt fencing for your project should only be tall enough to account for its installation on the contour of a steeper slope.

Post type

Wood posts have proven to be the most effective and reliable option for installing silt fencing. Although there are alternatives available, wood posts feature large cross sectional areas that help resist side loads, and limit the chance that heavy wind will tear the fabric. Fabric is easily attached with wide crown staples that are a much better option than using zip ties or wire ties with t-posts. In applications where the soil is too hard or rocky for installation of wood posts, t-posts are an acceptable substitute.

Post spacing

Cutting down the space between posts will significantly improve the strength of a silt fence. 10 feet is the maximum acceptable distance between each post. There are no applications where more distance is acceptable, but there are applications where less spacing is required. As an example, turns and low areas will need less space between fence posts. Installing posts 8-feet apart is recommended to ensure your silt fencing stands up to water runoff, strong winds, and other environmental stresses. The additional cost of adding more posts often offsets the cost of maintenance throughout the life of the fencing.

Post length

For typical applications, post length is almost always one-size fits all. Post length should only be 16 inches longer than the height of the silt fence fabric, which allows for the appropriate height needed to drive the post into the ground. This height gives the most benefit and stability to the silt fencing. There are no benefits to using a post more than 16 inches longer than your fencing. The strength limit of the stake is reduced beyond this length, and limits the amount of side load the fence can handle.

Wire backed

Traditionally, adding a wire backing to silt fencing is a great way to increase its strength and stability. Wire backing is typically recommended in high load areas. Posts for wire backed silt fencing should be no more than 6 feet apart. In order to be effective, wire should have a maximum opening of 6-inches by 6-inches and be constructed of at least 14.5-gauge. Wire doesn’t need to be buried to gain lateral support, but it should be in contact with the ground.

A New Generation of Silt Fencing

Agencies have turned to what the industry refers to as the “super silt fence” that is wire backed and designed to withstand the utmost hydraulic and sediment force loadings. However, WINFAB has developed an alternative solution we like to refer to as the next generation silt fence. Offering equivalent stiffness and strength of wire or chain-link backed silt fence, this new line of silt fencing is structurally enhanced to eliminate the need for reinforced wire-fence backing. It is specifically engineered to prevent excessive material elongation and strain, and withstand high-tensile stresses. The resulting product is a silt fence fabric that is able to resist fence deflection and avoid ultimate failure caused by sagging, ripping, or overturning from debris flows, overtopping, and excessive backwater depths. The next generation silt fence — high tensile modulus fabrics provide for a better performing green and economical alternative for supported silt fence applications.

Features and benefits include:

• Easier to install
• Performs equally to that of wire backed silt fence
• Reduces waste at the end of the project (there are lots of pictures out there of mangled up wire backed silt fence that has to go to landfills)
• Is domestically produced

Designed for filtration, separation, and erosion protection applications, WINFAB’s silt fence textiles are designed to help prevent drain system clogging and silt pollution in waterways, as well as reduce the velocity of storm runoff. Our geotextiles are easy to install and maintain, and are guaranteed to be environmentally friendly, ensuring that your project site remains compliant with the latest industry standards. Contact us today to learn more.