CEPSCI Construction Site BMPs and Implementation 1 — Questions and Answers
Question 1: What is the primary function of a silt fence?
- To divert clean water around a disturbed area
- To act as a barrier that slows sheet flow and allows sediment to settle out before runoff passes through (Correct answer)
- To stabilize stream banks
- To prevent wind erosion on flat areas
Correct answer: To act as a barrier that slows sheet flow and allows sediment to settle out before runoff passes through
Silt fences intercept sheet flow runoff, ponding water temporarily so sediment settles out before the filtered water passes through the geotextile fabric.
Question 2: Which of the following is a correct installation requirement for a silt fence?
- Install on slopes greater than 50% for maximum effectiveness
- Bury the bottom of the fabric in a trench and backfill to prevent undercutting (Correct answer)
- Install parallel to the slope contour at the top of the slope
- Leave a gap at each end to allow overflow
Correct answer: Bury the bottom of the fabric in a trench and backfill to prevent undercutting
Trenching and backfilling the fabric bottom prevents water from tunneling under the fence, which is the most common cause of silt fence failure.
Question 3: What is a 'construction entrance' or 'stabilized pad' BMP designed to do?
- Provide parking for construction vehicles
- Remove mud and dirt from vehicle tires before they exit the site onto public roads (Correct answer)
- Stabilize the soil beneath heavy equipment
- Mark the boundary of the construction zone
Correct answer: Remove mud and dirt from vehicle tires before they exit the site onto public roads
Stabilized construction entrances use crushed stone or other coarse material to knock mud off tires, preventing sediment tracking onto public streets.
Question 4: Hydroseeding is most effectively used as:
- A substitute for silt fences on steep slopes
- A temporary or permanent vegetative stabilization method applied as a slurry to exposed slopes (Correct answer)
- A sediment trapping device at storm drain inlets
- A technique for compacting disturbed soils
Correct answer: A temporary or permanent vegetative stabilization method applied as a slurry to exposed slopes
Hydroseeding delivers a mixture of seed, mulch, fertilizer, and water in a slurry that adheres to slopes, providing rapid vegetative cover for erosion control.
Question 5: When should temporary BMPs be removed from a construction site?
- As soon as the grading permit is issued
- After the disturbed area has achieved adequate permanent stabilization with established vegetation (Correct answer)
- At the end of each workday
- Before the first significant rain event of the season
Correct answer: After the disturbed area has achieved adequate permanent stabilization with established vegetation
Temporary BMPs should remain in place and be maintained until permanent vegetation or other stabilization is established and capable of controlling erosion without them.
Question 6: What is the recommended maximum drainage area for a silt fence installation?
- 10 acres of drainage area
- 0.25 to 1 acre per 100 linear feet, typically with slopes less than 50% (Correct answer)
- 5 acres per linear 100 feet
- There is no limit if the fence is tall enough
Correct answer: 0.25 to 1 acre per 100 linear feet, typically with slopes less than 50%
Silt fences are designed for small drainage areas and gentle to moderate slopes; exceeding design limits causes premature failure and loss of sediment control effectiveness.
CEPSCI Construction Site BMPs and Implementation 1
What is the primary function of a silt fence?