CPESC Vegetative Stabilization 4 — Questions and Answers
Question 1: Under NPDES permit requirements, within how many calendar days must temporary or permanent stabilization be initiated on areas where earth disturbance activities have temporarily ceased?
- 7 days
- 14 days (Correct answer)
- 21 days
- 30 days
Correct answer: 14 days
EPA's Construction General Permit requires initiation of stabilization within 14 calendar days after the last earth disturbance on areas where activities have temporarily or permanently ceased.
Question 2: What is the critical difference between temporary and permanent vegetative stabilization measures in an erosion and sediment control plan?
- Temporary measures use only mulch while permanent measures use only sod
- Temporary measures provide short-term cover during construction; permanent measures establish long-term self-sustaining vegetation (Correct answer)
- Temporary measures are only used on slopes while permanent measures are used on flat areas
- Temporary measures are installed before grading while permanent measures are installed after grading
Correct answer: Temporary measures provide short-term cover during construction; permanent measures establish long-term self-sustaining vegetation
Temporary stabilization controls erosion during active construction phases, while permanent stabilization establishes self-sustaining perennial vegetation that protects the site after construction is complete.
Question 3: Which practice best describes 'crimped straw mulch' and why is it superior to loose straw mulch on slopes?
- Straw chopped into fine particles and blown onto the slope; superior because it bonds to soil
- Straw pressed into the soil surface using a disk or crimping roller; superior because it resists wind displacement without tackifier (Correct answer)
- Straw soaked in water before application; superior because it provides more moisture
- Straw mixed with seed and applied hydraulically; superior because it ensures seed-mulch contact
Correct answer: Straw pressed into the soil surface using a disk or crimping roller; superior because it resists wind displacement without tackifier
Crimping mechanically anchors straw into the soil surface using a disk or toothed roller, eliminating wind displacement without the need for chemical tackifiers.
Question 4: A site inspector finds that a seeded area has reached 70% vegetative cover but has significant bare patches concentrated on north-facing micro-depressions. What is the MOST likely cause?
- Excessive fertilizer application
- Prolonged soil saturation in depressions inhibiting germination of the seed mix (Correct answer)
- Lack of sufficient sun exposure on the north-facing aspect
- Herbicide drift from adjacent areas
Correct answer: Prolonged soil saturation in depressions inhibiting germination of the seed mix
Low-lying depressions collect and hold water, creating waterlogged conditions that prevent germination and establishment of typical upland grass species in the seed mix.
Question 5: What is the purpose of specifying 'weed-free' certified straw mulch in an erosion and sediment control plan?
- To reduce the cost of mulch materials
- To prevent introduction of invasive plant species onto the disturbed site (Correct answer)
- To increase decomposition rate of the mulch
- To improve mulch bonding with the soil surface
Correct answer: To prevent introduction of invasive plant species onto the disturbed site
Weed-free certification ensures straw mulch does not introduce noxious weeds or invasive species that would compete with desired vegetation or spread onto adjacent lands.
Question 6: Which seeding technique involves placing seed in direct contact with the soil at a controlled depth using a tractor-pulled implement, and is most effective on relatively flat terrain with prepared seedbeds?
- Hydraulic seeding
- Broadcast seeding
- Drill seeding (Correct answer)
- Aerial seeding
Correct answer: Drill seeding
Drill seeding places seed at a precise depth (typically 1/4 to 1/2 inch) in direct soil contact using coulters and seed tubes, providing optimal germination conditions on accessible terrain.
Question 7: When vegetative cover on a stabilized site is inspected and found to have less than 70% cover at project closeout, what action is typically required under most state NPDES permits?
- The site may be closed out if no active erosion is visible
- Re-stabilization of bare areas and re-inspection before permit termination (Correct answer)
- Submission of a written variance request to the permitting authority
- Installation of permanent hard armor on all remaining bare areas
Correct answer: Re-stabilization of bare areas and re-inspection before permit termination
Most state CGP equivalents require a minimum of 70% uniform vegetative cover before permit termination; sites below this threshold must be re-seeded and re-inspected.
CPESC Vegetative Stabilization 4
Under NPDES permit requirements, within how many calendar days must temporary or permanent stabilization be initiated on areas where earth disturbance activities have temporarily ceased?