The Environmental Protection Agency lists sediment (soil particles in water) as the most common pollutant in rivers, streams, lakes, and reservoirs. Roughly 70% of the sediment in any body of water is from human land use and the other 30% is from natural erosion and deposition processes.
A method to minimize the amount of sediment escaping from large areas of disturbed soils, such as construction sites, is the use of filter socks.
Filter socks, or silt socks, are a fabric tube filled with compost or other recycled organic material. Filter socks are not all created equal.
There are compost filled filter socks, wood chip filled filter socks, and straw wattles. Each design of filter sock has a specific use and is not readily interchangeable. Filter sock to be used for perimeter controls should only be filled with well composted material. Non composted materials, such as straw and wood chips, are not acceptable.
Filter sock was developed as an alternative to silt fence and has several advantages of silt fence. First, filter sock filters sediment from stormwater runoff much faster than silt fence reducing standing water on construction sites. Filter sock also restricts the flow of storm water allowing for deposition to occur. Additionally, installation of filter sock is less labor intensive than silt fence as it does not require trenching and can be placed directly on the ground or pavement.
The Rainwater and Land Development manual from Ohio Department of Natural Resources states for most applications a 12” diameter filter sock will replace silt fence. See table 6.6.1 for specific applications and diameters.
Lastly, when removing filter sock from a project site the contents of the filter sock can be emptied onto the ground and leveled to match the surrounding grade then over seeded. No back filling trenches or settling to contend with.
Properly installed compost filled filter sock will minimize sediment-laden discharges and protect local streams and infrastructure.
Blog Author: Brian White, Urban Conservationist