Placement is important because where a fence starts, runs, and ends is paramount to gathering and detaining water. As little as 6 inches can miss a major vein of water, or allow water to run around an end and wash out the slope, making the fence a complete waste of money and causing more damage than no silt fence. Proper placement is often accomplished by creating an upturn, called a J-hook, on the end of a run to insure the water is detained for sedimentation to occur. Quantity refers to the proper ratio of silt fence to area protected. A good ratio is 100 linear feet of silt fence per 10,000 square feet of area.
Improper quantities have a direct relationship to silt fence failures.
Installation refers to the proper installation of fabric in the soil, and the creation of optimum conditions for compaction once installed. Again, a silt fence improperly installed is a complete waste of money. Fabric needs to be embedded deep enough in the soil to prevent under-cutting. Compaction refers to properly compacting the soil to prevent water-saturation, or piping. Compaction is achieved with the proper moisture, soil conditions, and fabric placement allowing mechanical compaction to take place.