CESSWI Erosion Control BMPs 2 — Questions and Answers
Question 1: Which factor most directly determines the appropriate spacing of contour wattles on a slope?
- Slope steepness and wattle diameter (Correct answer)
- Soil type and clay content
- Annual rainfall amount
- Proximity to water bodies
Correct answer: Slope steepness and wattle diameter
Spacing of contour wattles is primarily determined by slope steepness and wattle diameter, with steeper slopes requiring closer spacing.
Question 2: A hydroseeding operation fails to establish vegetative cover within the specified timeframe. What is the FIRST corrective action an inspector should require?
- Reapply hydraulic mulch and seed to bare areas (Correct answer)
- Install temporary silt fence around the entire disturbed area
- Require the contractor to install permanent hard armor
- Issue a stop-work order immediately
Correct answer: Reapply hydraulic mulch and seed to bare areas
Reapplying hydraulic mulch and seed to bare areas addresses the establishment failure directly and maintains the erosion control intent.
Question 3: What minimum ground cover percentage is typically required before temporary erosion controls can be removed from a stabilized slope?
- 70%
- 50%
- 85% (Correct answer)
- 60%
Correct answer: 85%
Most regulatory standards, including NPDES Construction General Permits, require 70–80% vegetative cover; 85% is the typical conservative threshold for final stabilization.
Question 4: Crimped straw mulch without tackifier is MOST effective when used in which situation?
- Flat to gently sloping areas with wind protection (Correct answer)
- Steep slopes greater than 3:1 (H:V)
- Active stream channels
- Areas with frequent vehicle traffic
Correct answer: Flat to gently sloping areas with wind protection
Crimped straw mulch without tackifier is best suited for flat to gently sloping areas where wind and slope forces won't dislodge it.
Question 5: Which erosion control BMP provides both sediment filtering and slope stability reinforcement simultaneously?
- Erosion control blanket (ECB) (Correct answer)
- Silt fence
- Rock check dam
- Inlet protection device
Correct answer: Erosion control blanket (ECB)
Erosion control blankets protect the soil surface from raindrop impact and runoff while also reinforcing slope stability as vegetation establishes.
Question 6: When inspecting a compost sock installation, which deficiency would be MOST critical to flag?
- Sock not staked and migrated downslope (Correct answer)
- Minor gaps between adjacent socks
- Slight overfilling of the sock casing
- Sock material color fading
Correct answer: Sock not staked and migrated downslope
An unstaked compost sock that has migrated downslope is no longer functioning as a contour barrier and must be repositioned and secured.
Question 7: On a construction site, polyacrylamide (PAM) is PRIMARILY used to:
- Flocculate fine particles and reduce turbidity in runoff (Correct answer)
- Stabilize steep cut slopes against mass movement
- Replace vegetative cover during dry seasons
- Filter petroleum hydrocarbons from stormwater
Correct answer: Flocculate fine particles and reduce turbidity in runoff
PAM is a soil amendment that causes fine clay and silt particles to clump (flocculate), reducing turbidity in stormwater runoff.
CESSWI Erosion Control BMPs 2
Which factor most directly determines the appropriate spacing of contour wattles on a slope?