Module 2 - Inspecting BMPs Flashcards
Purpose of sediment control
Minimize eroded soil from being carried off the site by a mobile agent
What is sediment control accomplished by
reducing runoff velocities
dissipating energy
providing an opportunity for sediments to settle
7 most common sediment control bmp types
Perimeter controls
Check structures
Inlet barriers
Turbidity barriers
Sediment containment systems
Stabilized construction entrances
Polymers
What is often forgotten for bale perimeter controls
backfill material - these are basically never installed correctly
T/F silt fence removes sediment by filtration
F: it may cause ponding for sedimentation
T/F silt fence should not be used where concentrated flows occur unless properly supported
T
What side should posts be placed for silt fence
Downstream side
T/F fibre rolls/logs should be placed on top of flat surfaces
F - should be in a depression and proper size used and staked
What is silt fence slicing
uses machines to place the silt fence, no need to worry about ends between fences
Compost berm/sock measurement standard
width needs to be 2x the height
Compost berm/sock for slopes 3h:1V
height should be 300-600 mm/12-24 inches
T/F Check structures are flat
F: should have a low flow line for runoff and high edges
Fibre log/rolls should be what diameter in drainage channel structures
300 mm
How to place check structures along a waterway for erosion control
spacing is critical for erosion protection, top of downstream structure must be in line with the bottom of the upstream structure
How to place check structures along a waterway for sediment control
spacing isn’t as critical as it would be for erosion control, removal of accumulated sediment must occur regularly, possible use of various erosion control BMPs or repair of eroded channel`
What conditions need to exist in order for placing barriers in front of an inlet to occur
sump conditions
If runoff is flowing under rock bags, what is causing it
large diameter rock diameter
Direction of straw and bindings in straw bale barriers
Bindings should never touch the ground and straw should be up and down
How to winterize inlet inserts
always empty the bag before freezes/thaws because bag can weaken and then flush all contents through the system
Purpose of in-stream controls
isolate the work area from the rest of the water body
How long can you store a stockpile
no more than 6-12 months because it can change microorganism activity
Purpose of sediment containment systems
contain runoff long enough to allow for deposition of suspended particles
Direction of turbidity barriers
parallel to water flow
How long should detention time be for sediment retention/detention structures
at least 24 hours
