Not to install silt fence barriers?

Not to install silt fence barriers?

• A. On level, well-vegetated ground.
• B. In areas with slope less than 5%.
• C. In front of stabilized outfalls.
• D. Where concentrated flows are expected (unless properly supported) and after construction activities are completed.

Answer: (D)

Silt fences are designed to intercept and slow down sheet runoff from disturbed areas so sediment can drop out before reaching water bodies. They work best on gentle, distribu­ted flow and when properly anchored and maintained. In areas where runoff becomes concentrated, the water speeds up and channelizes through a narrow path, which can overwhelm a silt fence. The barrier can be bypassed, undermined at the base, or fail to trap sediment effectively unless you provide substantial support and additional controls. Also, if construction has ended, there’s little ongoing disturbance generating sediment, so installing or leaving a silt fence offers little benefit and can hinder drainage or become a maintenance burden. In contrast, other controls like energy dissipation devices, diversion channels, or sediment basins are more appropriate for concentrated flows, and permanent stabilization replaces temporary practices once the site is stabilized.

Silt fences are designed to intercept and slow down sheet runoff from disturbed areas so sediment can drop out before reaching water bodies. They work best on gentle, distribu­ted flow and when properly anchored and maintained. In areas where runoff becomes concentrated, the water speeds up and channelizes through a narrow path, which can overwhelm a silt fence. The barrier can be bypassed, undermined at the base, or fail to trap sediment effectively unless you provide substantial support and additional controls.

Also, if construction has ended, there’s little ongoing disturbance generating sediment, so installing or leaving a silt fence offers little benefit and can hinder drainage or become a maintenance burden. In contrast, other controls like energy dissipation devices, diversion channels, or sediment basins are more appropriate for concentrated flows, and permanent stabilization replaces temporary practices once the site is stabilized.