A Sample of Erosion and Sediment Controls Found on Construction Sites
(Conservation Currents, Northern Virginia Soil and Water Conservation District)
A silt fence is a temporary sediment barrier made of woven synthetic filtration fabric supported by steel or wood posts. A silt fence should be installed below disturbed areas where erosion would occur in the form of sheet and rill erosion. It helps to contain sediment within the construction site. The bottom four inches of fabric must be buried beneath the soil surface to prevent sediment from going under the fence.
Double Silt Fence
The two silt fences prevent sediment from going into the tree
save area, which is further protected by a chain link fence.
Super Silt Fence
A super silt fence has metal poles, spaced 10 feet apart, supporting a chain link fence. The woven synthetic filtration fabric is stretched across its length. A super silt fence is sturdier and less likely to be breached than a regular silt fence.
The super silt fence prevents erosion of the slope from affecting the stream below.
No formal design is required, but several criteria must be considered to protect desirable trees from mechanical and other injury during land disturbing and construction activities. At a minimum, the limits of clearing shall be located outside the drip line of any tree to be retained and no closer than 5 feet to the trunk of any tree. Each tree to be saved must be marked at a height visible to equipment operators.
This is an unusual tree save area in that the trees were dug up and relocated by the builder for later replanting throughout the development.
When storm drain inlets are to be made operational before the site is stabilized, they must be protected to prevent sediment from entering the storm drain system. Depending on the type of inlet, protection devices may include sod, concrete blocks, stone, wire mesh, filter fabric and/or silt fencing.
A sediment basin is a temporary impoundment (reservoir) built to retain sediment and debris with a controlled stormwater release structure. A sediment basin controls drainage areas over three acres with a maximum allowable drainage area of 100 acres.
The nicely grassed sediment basin prevents eroded earth materials from leaving the construction site. A sediment basin differs from a sediment trap in that it serves a larger drainage area (three or more acres up to 100 acres.)
A temporary impoundment (reservoir) built to retain sediment and debris on a drainage area less than three acres. The sediment trap, on areas between one and three acres, is formed by building a predetermined reservoir confined by an earthen embankment with a pipe outlet. For areas less than one acre, a stone outlet is sufficient.
Dust control is necessary in areas subject to surface and air movement of dust from exposed soil. Irrigation with a water truck is a common dust control practice.
The truck is spraying water from the back.
Whenever traffic will be leaving a construction site and moving directly onto a public road or other paved area, there must be a stone construction entrance lined with filter fabric to reduce the amount of mud being transported off-site. If conditions on the site are such that most of the mud is not being removed from the vehicles by driving over the stone, then the tires must be washed, and the waste water carried away to a settling area.
Vehicles stop at the wash rack to have the tires hosed off. The muddy water drains through the grates to the settling area.
A diversion dike is a channel with a supporting earthen embankment on the lower side constructed across or at the bottom of a slope to intercept surface water runoff. Usually, the runoff is diverted into a sediment trap or sediment basin.
The nicely grassed berm keeps the runoff in the channel on site.
Made of tubing or a another conduit of nonerosive material, a slope drain extends from the top to the bottom of a slope with an energy dissipater at the outlet end. A slope drain prevents off-site and/or onsite runoff from eroding a steep slope by containing the runoff as it goes down the slope. (No picture available).