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Erosion and Sediment Control Systems M. D. Smolen Biosystems and Agricultural Engineering. † HTL. General Principals of Erosion and Sediment Control. First control erosion on site. Capture the sediment on site. Control outlet energy to prevent off-site damage.
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Erosion and Sediment Control Systems M. D. SmolenBiosystems and Agricultural Engineering †HTL
General Principals of Erosion and Sediment Control • First control erosion on site. • Capture the sediment on site. • Control outlet energy to prevent off-site damage.
Specific Erosion Control Principals • Limit extent and duration of grading • Protect the land surface • Divert runoff from upslope areas • Keep runoff velocities low • Construct stable channels
Establish the perimeter and buffer areas Phase grading to match the construction schedule
Protect the Surface • Use temporary or permanent vegetation • Apply mulch (fastened down)
Tracking is not used enough, and when used it is often done wrong. It should be up and down the slope.
Sometimes a nurse crop of small grain can help the permanent grass get started.
Divert Runoff from Upslope Areas • Use a diversion dike and channel. • Divert clean water Treating clean water is expensive! Work Area
Keep Velocities Low Limit slope length - use terraces and diversions
Never let flow cascade over a fill slope Use a chute, a pipe, or a channel to carry water down the slope
A chute can protect the slope, but high velocity water can erode down slope.
High velocity at the end of the chute can cause substantial erosion.
A temporary pipe drop can be extremely effective.
Construct Stable Channels • Steep channels should be lined. • Channels must be big enough to carry the flow. • Channels must be free of obstructions and protected from sediment.
Channel Liners • Temporary (fabric, straw with netting, excelsior) • Permanent (grass, riprap, gabions, concrete)
Capture Sediment Near the Source - the second line of defense • Barriers (Silt Fence, Hay Bales) • Inlet protection devices (Fabric) • Sediment Traps • Detention Basins
You cannot filter sediment-laden runoff! Filters clog too quickly with sedimentand fail. All sediment control device works by slowing the velocity causing the sediment to settle out.
Sediment Traps and Barriers • The trap is a small basin with a gravel outlet (controls up to 5 acres) • Barriers: silt fence, hay bales Inexpensive and effective, if installed properly and maintained
Silt fence are effective, but they... • Must be installed properly • Must be maintained • Require planning for good access • Require planning for sedimentation potential • Can’t handle concentrated flow • Need a good outlet
Silt Fence • Bury at least 6 in. • Use sturdy, steel posts every 6 ft. • Install on the contour. • 100 ft of fence per 1/4 acre. Inspect and repair frequently
Silt Fence • Provide settling area above the fence • Anticipate locations for deposition • Clean out and repair
Hay bales are not effective sediment barriers because: • They clog quickly • They decompose rapidly • They are difficult to install properly • They work – but only for a while They are best for temporary installations
Inlet Protection Devices • Area up to 1 acre • Should be supported at top • Must be buried 6 in at bottom • Requires maintenance after every storm
A System for Erosion and Sediment Control • Install control measures first. • Phase the grading. • Establish traffic pattern. • Protect cut and fill slopes • Stabilize the surface • Maintain the system.