Sediment Control BMPs Flashcards
7 cards from real CESSWI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Sediment Control BMPs flashcards as text
A polymer-enhanced sediment control BMP (such as PAM-treated straw wattles) works primarily by:
Answer: Causing fine clay particles to flocculate and settle faster
Polyacrylamide (PAM) and similar polymers cause fine clay particles to coagulate (flocculate), forming larger aggregates that settle much more rapidly than individual clay particles.
Which inspection frequency is typically required for sediment control BMPs during a period of active construction?
Answer: After every rainfall event of 0.5 inches or more, and at least weekly
Most NPDES construction general permits require BMP inspections after any storm event producing 0.5 inches or more of rainfall and at least once per week during active construction.
What is the MOST critical location to install sediment controls on a construction site draining toward a wetland?
Answer: At the perimeter of the disturbed area and at all discharge points near the wetland
Perimeter controls at the downslope boundary and at all potential discharge points near sensitive resources provide the last line of defense before sediment reaches the wetland.
Why is geotextile fabric specification (AOS) important when selecting a silt fence material?
Answer: AOS (Apparent Opening Size) controls which particle sizes are filtered versus passed through the fabric
Apparent Opening Size (AOS) specifies the equivalent pore size of the fabric; selecting the correct AOS balances sediment retention with hydraulic conductivity to prevent blowouts.
A site inspection reveals that silt fence posts are leaning at more than 30 degrees from vertical after a storm. The CORRECT corrective action is:
Answer: Remove accumulated sediment, pull posts back to vertical, and re-drive or replace
Leaning posts indicate overloading from sediment accumulation or hydrostatic pressure; the proper fix is to remove sediment and restore the fence to its original installed position.
What distinguishes a sediment trap from a sediment basin in terms of drainage area?
Answer: Sediment traps serve areas less than 5 acres; basins are required for 5 acres or more
Sediment traps are typically designed for drainage areas less than 5 acres, while sediment basins with engineered outlet structures are required for larger disturbed areas.
Which of the following BEST describes 'construction phasing' as a sediment control strategy?
Answer: Limiting the amount of land disturbed at any one time to reduce exposed soil area
Construction phasing limits the total acreage disturbed at any one time, reducing the source area generating sediment-laden runoff and the demand on downstream controls.