SILT FENCE

A silt fence, or filter fence, is a temporary sediment control device used on construction sites to protect water quality in nearby streams, rivers, lakes and bays from sediment (loose soil) in storm water runoff. A typical fence consists of a piece of synthetic filter fabric (also called a geotextile) stretched between a series of wooden or metal fence stakes along a horizontal contour level. The stakes are installed on the downhill side of the fence, and the bottom edge of the fabric is trenched into the soil and backfilled on the uphill side. The storm water slowly passes through the fence while depositing its sediments on the uphill side of the fence. The fence is not designed to concentrate or channel storm water. The fence is installed on a site before soil disturbance (earth moving) begins, down-slope from the disturbance area."

Some government jurisdictions in the United States recommend or require the use of a reinforced fence, sometimes called a "super" silt fence, on some construction sites. This design uses filter fabric reinforced by a wire mesh or chain link fence. The metal backing gives the fence increased strength to resist the weight of soil and water which may be trapped by the fence in a large drainage area, and also discourages construction site operators from driving vehicles over the fence. However, an improper installation of a super silt fence can create an inadvertent sediment basin if the filter fabric becomes clogged. This typically causes flooding, failure of the fence, and increased downstream pollution.

Silt fences are perimeter controls, typically used in combination with (properly designed) sediment basins and sediment traps, as well as erosion controls, which are designed to retain sediment in place where soil is being disturbed by construction processes.