Erosion controls – one size doesn’t fit all

Silt fence at South Market

While going through my computer looking for a picture, I came across one of my favorite Silt Fence Photos. This one, taken in March 2005, is from the South Market development site, on the west side of Route 15 south of Haymarket.

This particular silt fence was installed along the edge of a road project in an area that was not identified as a Jurisdictional Wetland, which means no wetland permits or mitigation were required.

These inexpensive, plastic fences are the most common erosion control seen at local development sites, regardless of site conditions. The one shown in the photo isn’t doing much of anything but, even when they’re correctly installed and in the right place, silt fences have limited value.

How well silt fences work is directly connected to soil types and varies greatly from site to site. According to the EPA, they are pretty good at removing sand, with an 80-90% success rate. For silt-loam soils, removal varies from 50% to 80%, depending on landscape and other conditions. Things are far worse in areas with silt-clay-loam soils, where silt fences are only 20% effective at best.

Prince William has a remarkably diverse landscape, and soil types, that transition from coastal plain to piedmont ecosystems. From east to west, elevations rise from sea level to 1,280 feet at Bull Run Mountain. Prince William isn’t a one-size-fits-all kind of place for erosion controls.

According to the EPA, soil is the number one pollutant in waterways. Instead of relying solely on silt fences, a menu that includes a variety of erosion control options, standards based on soil types and a regular inspection schedule for all denuded areas could save Prince William taxpayers considerable sums in clean up and restoration costs.


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