CPESC BMP Selection 4 — Questions and Answers
Question 1: Which BMP is best suited to protect a stormwater inlet located in a paved parking lot during active grading nearby?
- Silt fence staked around the inlet
- Filter fabric inlet insert or gravel-bag barrier (Correct answer)
- Temporary seeding adjacent to inlet
- Concrete block barrier
Correct answer: Filter fabric inlet insert or gravel-bag barrier
Filter fabric inserts or gravel-bag barriers are designed to fit within or around paved inlets, filtering sediment while allowing flow to continue.
Question 2: During BMP selection, the concept of 'treatment train' refers to:
- Using a single large BMP to handle all runoff
- Applying multiple BMPs in sequence to progressively reduce pollutants (Correct answer)
- Scheduling BMP installation in sequential phases
- Training workers to install BMPs in the correct order
Correct answer: Applying multiple BMPs in sequence to progressively reduce pollutants
A treatment train uses multiple BMPs in series so each successive control further reduces sediment and pollutant loads before discharge.
Question 3: A site has a 10-acre disturbed area draining to a single point. According to common design standards, which structure is typically REQUIRED at this scale?
- Sediment trap
- Silt fence perimeter
- Sediment basin (Correct answer)
- Fiber roll check dam
Correct answer: Sediment basin
Sediment basins are typically required when the contributing drainage area exceeds 5 acres, making a basin mandatory for a 10-acre site.
Question 4: Which BMP is most effective at protecting bare soil slopes from raindrop splash erosion during initial land disturbance?
- Silt fence at the slope toe
- Erosion control blanket (ECB) pinned to the slope surface (Correct answer)
- Rock check dam in the swale
- Diversion dike at the slope crest
Correct answer: Erosion control blanket (ECB) pinned to the slope surface
Erosion control blankets protect the soil surface directly from raindrop impact and sheet flow while vegetation establishes underneath.
Question 5: When selecting polyacrylamide (PAM) as a BMP, which application method is recommended to prevent aquatic toxicity?
- Broadcast dry granules directly into receiving streams
- Apply anionic PAM to soil or runoff, never directly to waterways (Correct answer)
- Mix cationic PAM with stormwater before discharge
- Spray PAM aerially over the entire watershed
Correct answer: Apply anionic PAM to soil or runoff, never directly to waterways
Only anionic PAM is approved for erosion control, and it must be applied to soil or runoff on-site — never directly into waterways — to avoid aquatic toxicity.
Question 6: A check dam installed in a drainage swale is intended primarily to:
- Filter sediment through geotextile fabric
- Reduce flow velocity and trap coarse sediment (Correct answer)
- Divert flow away from the swale
- Measure the volume of runoff passing through
Correct answer: Reduce flow velocity and trap coarse sediment
Check dams reduce flow velocity within the swale and cause coarse sediment to drop out immediately upstream of the structure.
Question 7: For a construction site in a karst topography region, which additional BMP consideration is most critical?
- Increasing the height of silt fence
- Preventing sediment-laden water from entering sinkholes or fractures (Correct answer)
- Adding extra layers of straw mulch
- Installing deeper sediment basin risers
Correct answer: Preventing sediment-laden water from entering sinkholes or fractures
In karst areas, runoff can rapidly enter sinkholes and fractures, bypassing surface treatment, so BMPs must specifically prevent direct introduction of sediment into these features.
CPESC BMP Selection 4
Which BMP is best suited to protect a stormwater inlet located in a paved parking lot during active grading nearby?