module 4: temporary sediment controls. learning objectives n identify locations for sediment control...

Module 4: Temporary Sediment ControlsModule 4: Temporary Sediment Controls

Learning Objectives Learning Objectives

Identify locations for sediment control BMPs

Identify applications for different types of sediment control BMPs

Identify installation requirements for sediment control BMPs

Groups of BMP TechniquesGroups of BMP Techniques

Soil Stabilization

Sediment Control

Other BMPs

• Tracking Controls

• Wind Erosion Controls

• Non-Storm Water Management

• Materials and Waste Management

Sediment Control BMPs IntroductionSediment Control BMPs Introduction

Filtration: Silt Fence BMP

Basins and Traps: Desilting Basin, Sediment Trap, and Check Dam BMPs

Removal: Street Sweeping and Vacuuming BMP

Interception: Fiber Rolls, Gravel Bag Berm, Sand Bag, and Strawbale BMPs

Inlet Protection BMP

Silt Fence BMP (SC1)Silt Fence BMP (SC1)

Field Manual –Page 62

Silt Fence BMP (SC1) Silt Fence BMP (SC1)

Use

Toe of bare slopes

Down slope of exposed soil stockpiles along critical areas such as streams


Limitations

Not in mid-slope locations or slopes steeper than 4:1

Maintenance required

Not for large water volumes

Not for live streams


Additional Considerations

Keying in fence (vertical entrenchment or ‘L’ entrenchment)

Stabilized or unstabilized installation

Proper positioning

• Toe of slope

• On the contour

Silt Fence BMP Detail (SC1)

Silt Fence BMP Detail (SC1)

Silt Fence Cross Section

Silt Fence Oblique View

Anchor Trench

Support Fencing


Desilting Basin (SC2)Desilting Basin (SC2)


Use

Sediment may enter drainage or watercourse (cannot be used within a waterway)

Drainage area is between 2 and 4 ha (5-10 acres)

Failure will not cause loss of life or property



Limitations

Requires large surface area for settlement

Cannot be located in live stream

May be a safety concern requiring fencing

Risk of failure under high flow conditions



Locate where permanent detention basins will be

Size

capacity equal to 100 m3 of storage per hectare

length more than twice the width

1 to 1.5 m depth


Additional Considerations (cont)

Overflows or bypasses protected from scour

Drainage within 72 hours following storm events

• Access for maintenance

• Inlet protection: rock or vegetation

• Forebay to collect debris

• “High hazard” Basins must be approved by P.E.

Desilting Basin BMP Detail (SC2)

Desilting Basin BMP Detail (SC2) Stabilized Outlet

Emergency Spillway

Stabilized Inlet

Field Manual –Pages 70 and 71

Sediment Trap (SC3)Sediment Trap (SC3)


Use

Located across a drainage way

Excavated/constructed of earthen material

For drainage areas < 2ha



Limitations

Requires large surface area to permit settling

Not appropriate for drainage areas > 2ha

Hazardous; may require fencing

Not appropriate in live stream

May be a safety concern requiring fencing



Use where failure will not cause loss of life or property

Capacity and Dimensions

Settling zone: 130 m3/ha of drainage area

storage zone: 65 m3/ha of drainage area

Length to width >3:1


Additional Considerations (cont)

Basins >1,000m3 and/or levees >1.5m must be approved by registered PE

Must have access for maintenance

Sediment Trap BMP Detail (SC3)

Sediment Trap BMP Detail (SC3)

Sediment trap

Stabilized Oultet


Check Dams (SC4)Check Dams (SC4)



Use

Located across a drainage way

Constructed of rocks, sandbags, or fiber rolls

Small channels and drainage areas < 4ha

Can be used in steep channels with high runoff velocities

In association with grass-lined channels


Limitations

Not appropriate for channel areas > 4ha

Not in live stream areas or well-vegetated channels

Will require maintenance after high flows

Sediment can be re-suspended

Not to be constructed using silt fence


Dam height and spacing

Safely pass high stormwater flows

Remove when grass established

Hand work may be required to shape dam


Check Dams BMP Detail (SC4)

Check Dams BMP Detail (SC4)

Check Dam Cross Section

Lowered Center Spillway


Dugout Ditch Basin BMP (SC11)Dugout Ditch Basin BMP (SC11)

Sediment Control Basin



Use

One or a series of small dugout basins located within a flow channel

Reduce runoff velocity, promote sediment retention

Sediment traps, interceptor ditches, toe of slope protection

Spacing dependent on ditch slope


Limitations

Not to be used in live streams

Not to be used in vegetated channels

Require maintenance

Trapped sediment can be resuspended during subsequent storms



Designed for 2-year, 24 hour rain event

Can remain in place and seeded with permanent seeding of ditch

Dugout Ditch Basin BMP Detail (SC11)

Dugout Ditch Basin BMP Detail (SC11)

Cross Section

Dugout basins


Fiber Rolls (SC5) and Gravel Bag Berm (SC6) Fiber Rolls (SC5) and Gravel Bag Berm (SC6)

SC5 - Field Manual –Page 79

SC6 - Field Manual –Page 82

Fiber Rolls (SC5) and Gravel Bag Berm (SC6)Fiber Rolls (SC5) and Gravel Bag Berm (SC6)

Use

Designed to shorten slope lengths and intercept and slow sheet flow, reduce flow velocity, and trap and remove some sediment

Fiber Rolls - straw, flax, rolled and bound

Gravel Bag Berms - a single roll of gravel bags

Used on the face of slopes, at the top of slopes, and at grade breaks


Limitations

Gravel Bags may rupture when removed, are laborious to install, and have limited durability for long projects

Fiber rolls may not degrade in the short term


Locate on level contour

Fiber rolls are typically left in place

Gravel bag berms may be removed


Fiber Rolls

Fiber Rolls BMP Detail (SC5)Fiber Rolls BMP Detail (SC5)

Roll Anchored in Trench

Rolls placed on contour


Gravel Berm Bag BMP Detail (SC6)

Gravel Berm Bag BMP Detail (SC6)

Gravel Bags placed on contour


Street Sweeping and Vacuuming (SC7)Street Sweeping and Vacuuming (SC7)



Use

Remove tracked soil to prevent it’s entry into storm drain or watercourse

Limitations

Not effective in wet conditions

May require daily treatment




May collect hazardous materials

Sandbag Barrier (SC8)Sandbag Barrier (SC8)



Use

Linear barrier of stacked sandbags

Slows sheet water flow

Increases detention time and sedimentation


Limitations

Installation can be labor intensive

Only where the up-gradient area is small (i.e., < 2 ha)

Limited durability



To create a temporary sediment basin

As sediment berms in stream beds (< 2ha)

When extended construction period limits the use of either silt fences or straw bale barriers

Along the perimeter of vehicle and equipment fueling and maintenance areas or chemical storage areas

To capture and detain non-storm water flows until proper cleaning operations occur

Sand Bag Barriers BMP Detail (SC8)

Sand Bag Barriers BMP Detail (SC8)

Plan View

Lowered Center Spillway


Straw Bale Barriers (SC9)Straw Bale Barriers (SC9)



Use

Linear barrier of straw bales designed to intercept and slow sheet flow

Increases on-site detention time and sedimentation

Along the perimeter of site and stream channels

Along roadways and around stockpiles

Across minor swales


Limitations

Not in channels or live streams with high flows

Labor intensive installation and removal

Maintenance intensive (disintegration)

Can not be used on paved surfaces

Drainage area small (<100m) slopes short (30m)



Wooden stakes used to anchor bales to soil

Bales embedded into soil

Install bales on the contour

Tightly abut bales

Offset second rows of bales when used

Straw Bale Barriers BMP Detail (SC9)

Straw Bale Barriers BMP Detail (SC9)

Bales embedded in soil

Bales overlapping

Bales anchored with stakes


Storm Drain Inlet Protection (SC10)Storm Drain Inlet Protection (SC10)



Use

Devices used to prevent sediment from entering storm drains

Used with other BMPs as the last defense

Appropriate Use:

Where ponding of water will not cause flooding

During wet and snow-melt seasons

Need to allow water into inlet


Limitations

Last line of defense

High flow may damage

Heavily sediment laden storm water may plug

Adversely effected by ponding


Various BMPs applicable to sediment control

Filter fabric

Sandbags

Straw bales

Gravel check dam


No inlet protection

Filter Fabric Application

Storm Drain Inlet Protection BMP Detail (SC10)


Straw Bale Application Filter Fabric

Application




Sand Bag Application

Gravel Check Dam Application


Summary of SC BMPsSummary of SC BMPs

Toolbox of different techniques

Need to be adapted to site conditions

Capture sediment from runoff

Require maintenance

Generally removed after vegetation established

Discussion photoDiscussion photo

The end of Sediment Control BMPsThe end of Sediment Control BMPs

Discussion

module 4: temporary sediment controls. learning objectives n identify locations for sediment control...

Documents

desilting basin bmp

maintenancesediment

silt fence bmpbasins

fence vertical entrenchment

m3ha of drainage arealength

live streammay

large water volumesnot

check dams sc4uselocated