CPESC Erosion Control Methods & Techniques 2 — Questions and Answers
Question 1: Which erosion control blanket (ECB) category is most appropriate for slopes steeper than 3:1 with high rainfall intensity?
- Category 1 (open-weave textile)
- Category 2 (erosion control blanket)
- Category 3 (turf reinforcement mat)
- Category 4 (high-performance TRM) (Correct answer)
Correct answer: Category 4 (high-performance TRM)
Category 4 high-performance TRMs provide permanent reinforcement for steep slopes and high-velocity flows where lower categories cannot maintain stability.
Question 2: What is the primary mechanism by which polyacrylamide (PAM) reduces erosion when applied to bare soil?
- It forms a waterproof crust that prevents infiltration
- It flocculates soil particles and increases aggregate stability (Correct answer)
- It repels raindrops before they reach the soil surface
- It accelerates vegetation establishment through fertilization
Correct answer: It flocculates soil particles and increases aggregate stability
PAM works by binding soil particles together, increasing aggregate stability and reducing detachment and transport by water.
Question 3: A check dam constructed with rock riprap in a drainage swale is designed primarily to:
- Permanently redirect flow to a vegetated filter strip
- Reduce flow velocity and trap sediment behind the structure (Correct answer)
- Increase flow velocity to prevent sediment deposition in the swale
- Filter dissolved pollutants from stormwater runoff
Correct answer: Reduce flow velocity and trap sediment behind the structure
Rock check dams reduce the velocity of concentrated flow, allowing sediment to settle out behind the dam.
Question 4: During which phase of construction activity is soil most vulnerable to erosion?
- Site clearing and grading when vegetation is removed (Correct answer)
- Foundation excavation when soil is compacted by equipment
- Building construction when impervious surfaces are installed
- Final landscaping when topsoil is spread
Correct answer: Site clearing and grading when vegetation is removed
Clearing and grading removes protective vegetation and disturbs soil structure, leaving bare erodible soil exposed to rainfall and runoff.
Question 5: What is the recommended maximum slope length for rolled erosion control products (RECPs) used without additional anchoring on a 4:1 slope?
- 25 feet
- 50 feet
- 100 feet
- It depends on the specific RECP and site conditions (Correct answer)
Correct answer: It depends on the specific RECP and site conditions
Maximum slope length for RECPs varies by product type, soil erodibility, rainfall intensity, and slope gradient, requiring site-specific evaluation.
Question 6: Hydromulching with wood fiber mulch at 2,000 lb/acre is most effective when:
- Applied to frozen ground before spring thaw
- Combined with a tackifier and applied to seeded slopes (Correct answer)
- Applied without seed to maximize mulch depth
- Used as a substitute for erosion control blankets on steep slopes
Correct answer: Combined with a tackifier and applied to seeded slopes
Hydromulch combined with a tackifier applied over seeded areas creates a protective matrix that holds seed in place and retains moisture for germination.
Question 7: Which factor most significantly limits the effectiveness of revegetation as a long-term erosion control measure in arid climates?
- High soil pH that prevents nutrient uptake
- Limited water availability for plant establishment and survival (Correct answer)
- Rocky substrate that prevents root penetration
- Excessive wind that removes seed before germination
Correct answer: Limited water availability for plant establishment and survival
In arid climates, insufficient moisture is the primary limiting factor for plant establishment and long-term vegetation cover.
CPESC Erosion Control Methods & Techniques 2
Which erosion control blanket (ECB) category is most appropriate for slopes steeper than 3:1 with high rainfall intensity?