20 JulHow to Select the Right Silt Fence For Your Site
Silt Fence is a requirement for most construction sites in the Mid-Atlantic and Southeast. This permeable fence filters stormwater runoff and retains sediment on the construction site. That is why it is installed around the site perimeter, especially in low lying, sensitive areas.
There is a lot of variation in erosion control fence specifications and standards. The fabric type, fence height, post spacing and post type are all subject to variation. That can make it difficult to know which fence to use on site.
That’s why we’re providing a few tips to help you select the right fence for your site.
Set yourself up for success by following these tips:
- Review the project plans
- Familiarize yourself with your local, municipal and state specifications
- Learn why and how to reinforce
Review Project Plans
Construction plans typically contain a Stormwater Pollution Prevention Plan (SWPPP). This plan outlines how the responsible land disturber controls runoff and erosion on the job site. The SWPPP includes an Erosion and Sediment Control Plan. These plans include drawings, specifications and details about the BMPs which includes Silt Fence.
Identify Silt Fence on Project Plans
The project plans will identify where and how to install silt fence. Unfortunately, there is not a universal symbol for Silt Fence.
For example, here are two different variations.
Construction plans will provide a legend and some will even label the plan.
Here is an example of a recent project our Estimators reviewed.
On this project, fence surrounds the storage and stockpile areas.
The legend also notes that the Silt Fence should meet Spec #3.05. You will find specifications and drawings in the Erosion Control Notes and Details.
The following two images are drawings for the same project.
From plate 3.05-2 we learn
- The fence does not need wire support
- The wood stakes should be spaced no more than 6 feet apart
- How to trench in the material
Some drawings, like Plate 3.05-1, also include details about the fabric, the reinforcement and the line poles.
Plan reading involves connecting a lot of pieces of information. Some plans clearly state the silt fence requirements while other plans will leave it more open-ended.
If your plans don’t identify the specified fabric you may find that information in a project specific specification book. This resource may be provided with the plans or by the project engineer.
If it is still unclear, consult local or state standards. State Department of Transportation standards for Silt Fence are typically more stringent on erosion control specifications.
If you need assistance with your project plans, you can send them to our sales team. One of our estimators will take a look and provide quotes based on the standards and specifications.
Know Your Local and State Specifications
Each state has an environmental division that protects and regulates activities that affect the environment.
These departments set standards for controlling runoff and maintaining clean stormwater during construction related activity. Most states’ Department of Transportation (DOT) also set standards for construction activity.
Like most construction standards, Silt Fence specifications vary from state to state. Familiarize yourself with the state environmental standards and the DOT standards to cover all bases.
DOT Silt Fence Fabric
In Virginia, the Virginia Department of Transportation (VDOT) Silt Fence fabric must be a pre-approved product on List Number 63 of the Materials Approved List .
You will notice that it is classified under Geosynthetics for Virginia. That is because Silt Fence is technically a geotextile fabric. For that reason, many state will list the approved Silt Fence fabric under their Geotextiles approval lists.
Fabric requirements are subject to change so it is important to monitor approvals. We monitor these changes and provide cheat sheets for purchasing DOT approved products. We provide Buying Guides for the following Mid-Atlantic states:
- West Virginia
You can find our DOT Buying Guides on our Resources page.
Silt Fence Installation Standards
State DOTs also have Silt Fence installation standards. In Virginia, the Roads and Bridges Specifications Book describes installation standards.
Silt Fence must either meet Type A or Type B Standards and be according to the EC-5 Standard Drawing.
As you can see here, the drawing outlines the requirements for post type, post spacing, fabric height and situational requirements and more.
Recent Change to VDOT Standards
In 2019, VDOT revised their silt fence standard in order to align more closely with AASHTO’s standards.
The new standard states:
- Type A should use wood posts spaced a maximum of four feet apart
- Type B Silt Fence should use steel posts, spaced a maximum of four feet apart
The new standard for Type A and Type B Silt Fence should be used for projects bid after April 2019 or if the VDOT engineer requires the new standard.
The previous standard can still be applied for projects bid before April 2019.
The previous standard states:
- Type A should use wood or steel posts spaced a maximum of six feet apart
- Type B should be reinforced with welded wire and use wood or steel posts spaced a maximum of ten feet apart.
These are big changes for installation requirements. If the wrong standard is applied, contractors risk losing time and money replacing the silt fence. This exemplifies why it is so important to stay on top of DOT standards.
Reinforce Sensitive Areas
Some areas of your site might require additional reinforcement.
Use reinforcement for the following locations:
- Sensitive areas like wetlands
- Installations at the bottom of hills or slopes
- Areas subject to high concentrated flow
These locations will be noted on your project plans and should be identified by a unique symbol for reinforced fence.
Different states and projects will require different reinforcement products. Many Mid-Atlantic projects specify a wire fence like Chain Link, Welded Wire or Hog Wire.
In Virginia, Super Silt Fence is a common wire reinforced fence. Super Silt Fence includes Silt Fence fabric, Chain Link and Galvanized Line Poles. This reinforced barrier is ideal for sensitive areas and locations that are subject to high velocity flow or a high volume of drainage.
Reinforcement is not limited to wire fence.
On a Virginia renewable energy project, the erosion control fence was reinforced with Welded Wire and backed by an 18” Compost Filter Sock. The Compost Filter Sock was an alternative to a Straw Bale barrier.
Reinforcement products like wire fence and compost filter sock are a key component of erosion control. If you think you need additional reinforcement for your temporary fence, our sales team can make suggestions that are custom to your site’s needs.
One last tip
As you can see, there is a lot of variation in Silt Fence standards. To keep it simple, we mostly covered Virginia standards but our scope expands well beyond our home state.
If you need help selecting fence for your Mid-Atlantic project, ask us for help.
We can review plans, provide estimates and make cost saving suggestions.