Silt fences (or sediment fences) are installed to help control sediment and rill erosion within exposed soil on construction sites by providing a temporary sediment barrier. Silt fences are designed to prevent dirty water from washing into our local waterways during rain events. A single building site can lose truckloads of soil in one storm event.
It is therefore critical, Silt fences are installed correctly to ensure they effectively capture sediment and protect the water quality of our local streams and waterways. To do this, there are a few things to consider.
Silt fence material
Silt fence material is a permeable geotextile fabric that helps capture sediment and slow down the water flow. To work effectively under the strain caused by rain events, it is important the silt fence material is extremely strong and durable. Aussie Environmental provides two geotextile options for different applications, Woven Polypropylene geotextile & a natural biodegradable Jute geotextile.
UV Stabilised Woven Polypropylene
Polypropylene, which is also known as PP for short name, is a thermoplastic resin material that is produced by the polymerization of propylene which is woven into strips/threads to create a light, but strong and heavy duty material. Due to the materials strength and light-weight it is the most commonly used Geotextile material for Silt Fencing.
Aussie Environmental’s polypropylene is UV stabilised and made from 100% virgin PP granules.
EcoFence Jute Geotextile
Aussie Environmental’s EcoFence is a more eco-friendly alternative to plastic (polypropylene) silt fence. Made from 100% biodegradable Jute Geotextile, EcoFence material is ideal for riparian zones and floodplain areas where once installed, it can be left in the environment to naturally break down over time.
Optimal posts for silt fence material
The best type of posts to hold up and secure the geotextile material is hardwood 900mmx 50mm x 25mm timber stakes. There are other types of posts on the market, but at Aussie Environmental, we have found that hardwood timber posts work the best. Timber posts have large cross-sectional areas to resist side loads and the material can be attached securely using wide staples. We have often seen zip or wire ties used, but these aren’t as effective as staples. For most soils, hardwood timber posts are the posts of choice, because they are long lasting and help to secure the silt fence in high winds.
Optimal spacing of the posts
To ensure that these sediment fences work correctly and meet best practice, the posts need to be spaced at a maximum 2 meters apart. If the stakes are spaced any further apart the fence is at risk of becoming compromised; with the runoff finding spaces underneath the fence and eroding the soil. For high flow areas, closer spacing of timber stakes is recommended to secure the fence. The additional cost of a few extra posts is off-set by the knowledge that your fence will withstand higher flows and strong winds and not need any repairing.
Optimal height of the posts
In general, the height of the posts needs to be at least 40cm longer than the geotextile material, as this allows 40cm of the post to be driven into the ground, making it very secure. For silt fence installation, Aussie Environmental has 900mm hardwood timber fence posts that are tailored to suit the height required for the silt fence material to work effectively and for the posts to be stable in the ground.
Silt Fence positioning
Silt fences should be installed on a site before soil disturbance (earth moving) begins, down-slope from the construction area or stockpile. They should always be installed along the contour of the slope you are protecting considering the likely runoff volume (catchment area).
If installing a silt fence on a downward slope you should be constructing “silt fence returns” or “j’s”, positioned perpendicular to the silt fence.
Step by step installation
For step by step installation instructions please find more information here: https://aussieenvironmental.com.au/product/hi-vis-orange-safety-silt-fence-87cmx50m-roll/
Aussie Environmental has been supplying and installing quality sediment control fences for more than 10 years. Our installations are fast, affordable and efficient. Call us on 07 5315 5431 for more information.