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Erosion Control

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martin888888

Civil/Environmental
Jun 15, 2010
157
Erosion control blankets are good to stabilize steep slopes to avoid runoff to natural areas. Are they needed in areas like steep slopes within a landfill or the slopes of the internal side of a detention pond, etc.?
 
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They are often used for slopes in retention/detention facilities. I have specified them several times for that purpose and for slopes leading to other bodies of water.
 
two kinds of mats are available.

Type 1 (cheap) is used to provide minimal erosion control and mostly helps the vegetation to become established. Seeding is required and the vegetation provides the erosion control. Hydroseed / hydromulch might be a good alternative.

Type 2 (expensive) is a turf reinforcement mat which provides considerable erosion control, even without any vegetation. Seeding and mulching are required.
 
Runoff is going into natural areas regardless. Erosion control blankets stop the erosion and sediment being transported. I can't count the number of detention basins I've seen with gulleys down the side. In a good (e.g. 1 yr return period) storm it doesn't take much to get the velocity required to erode a 3:1 slope... maybe 3 feet. The sediment collects in the bottom of your pond reducing the storage volume. It's a toss-up between sod and a blanket for cost. Sod is cheaper depending where you are and the season.
 
sod is only cheaper if you don't have to mow it. However, goats work cheap
 
Generally speaking slopes at 4:1 or more gradual should not need blankets. Anything steeper than that, than the soil types, water sources and monitoring schedule should be considered. A good granular soil will limit surface erosion and encourage quick vegetation. A clay soil will erode quickly and will not naturally vegetate quickly. If you can continuously water the slopes and provide regular maintenance/repair of minor slope failures, then slopes steeper than 4:1 may not require blankets.

But most of the time our clients do not maintain the slopes, do not irrigate the slopes, and we very rarely are dealing with non-erosive soils. So, unless you have a project with those unique characteristics, blanketing all soils steeper than 4:1 is a good practice.
 
if the slope is fill, the fill slope should be properly constructed otherwise it's only a bandaid on the problem.
 
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