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Erosion Control Increasingly Important For Utility Construction
The ubiquitous, low fences around perimeters of construction sites are so common these days they don’t draw the attention they once did. Every construction site on which the earth must be excavated or otherwise disturbed has one or several such fences, but their function often is misunderstood.
From a distance the fencing material appears to be plastic sheeting, but it actually is a geotextile fabric that allows water to flow through. While the material does to some extent filter storm water runoff during heavy rains, the primary purpose of the fence is to cause rainwater to “pond” -- collect in pool -- so that sediment can settle and not run off site and pollute the nation’s surface waters.
To accomplish that, these erosion-control fences -- commonly called silt fences -- must be positioned in accordance with an erosion control plan that complies with guidelines of the U.S Environmental Protection Agency’s (EPA) National Pollutant Discharge Elimination System (NPDES) permit program, usually administered by the state in which the project is located. Local regulations may also apply.
Public utilities usually obtain the permits for water and sewer construction. Providers of electrical, natural gas and telecommunications services are responsible for permitting for their projects. Typically, erosion control plans are developed by the project’s consulting engineering firm which also handles permitting.
A silt fence is composed of the geotextile fabric, sometimes reinforced with a wire mesh backing, and attached to wooden or metal stakes. The fabric is buried several inches in the ground.
Every construction site is different, and an erosion-control plan must take into account the area’s topography. A variety of erosion-control measures may be employed, including contouring the surface, hydromulching, erosion-control blankets and planting vegetation to hold soil in place. However, silt fences are most common and certainly the most visible method of erosion control. Silt fences usually are located along perimeters of work sites, but also may be installed elsewhere within a site both as barriers and to direct flow of runoff water. A common configuration of fences is to install them in a “J-hook” pattern to create the ponding area.
Erosion control work may be performed by the general contractor or subcontractors. Fence construction can be categorized as underground construction because a critical element in correctly installing an erosion-control, or silt fence, is firmly securing the bottom portion of the geotextile fabric in the ground.