CSM CSM Erosion & Sediment Control 1 — Questions and Answers
Question 1: What is the primary purpose of a silt fence installed at a construction site?
- To intercept sediment-laden runoff and allow sediment to settle before water leaves the site (Correct answer)
- To prevent workers from entering hazardous zones
- To direct stormwater into underground pipes
- To mark property boundaries during construction
Correct answer: To intercept sediment-laden runoff and allow sediment to settle before water leaves the site
A silt fence is a temporary sediment control device that intercepts sheet flow runoff, slowing it down so suspended sediment can settle out before the water leaves the site.
Question 2: Which temporary erosion control practice is most appropriate for stabilizing steep disturbed slopes during construction?
- Hydroseeding with tackifier (Correct answer)
- Installing silt fences horizontally
- Placing rock check dams at the slope base only
- Grading the slope to increase steepness
Correct answer: Hydroseeding with tackifier
Hydroseeding with a tackifier bonds mulch and seed to steep slopes, providing immediate surface protection while vegetation establishes.
Question 3: What is the function of a sediment basin on a construction site?
- To collect and detain runoff so sediment can settle before discharge (Correct answer)
- To store clean water for dust suppression
- To divert runoff away from the construction area
- To provide a staging area for excavated material
Correct answer: To collect and detain runoff so sediment can settle before discharge
A sediment basin temporarily impounds runoff from disturbed areas, allowing suspended sediment to settle before the clarified water is discharged.
Question 4: According to best practice, when should temporary erosion and sediment controls be installed on a construction site?
- Before or simultaneously with land disturbance activities (Correct answer)
- After rough grading is complete
- Only during the rainy season
- When a regulatory inspector visits the site
Correct answer: Before or simultaneously with land disturbance activities
Temporary controls must be in place before or at the time land is disturbed to prevent erosion and off-site sediment discharge from the very start of grading.
Question 5: What is the primary purpose of installing check dams in a drainage channel or swale?
- To reduce flow velocity and allow sediment to deposit upstream of the dam (Correct answer)
- To increase flow velocity and prevent channel clogging
- To permanently redirect runoff to a different watershed
- To measure total water volume passing through the channel
Correct answer: To reduce flow velocity and allow sediment to deposit upstream of the dam
Check dams slow channel flow velocity, reducing erosive energy and causing suspended sediment to settle in the pool formed upstream.
Question 6: Which material is most commonly used as a stabilized construction entrance to reduce tracking of mud onto public roads?
- Crushed stone or gravel pad (Correct answer)
- Compacted native soil
- Concrete poured over geotextile
- Wood chip mulch
Correct answer: Crushed stone or gravel pad
A stabilized construction entrance uses crushed stone or aggregate over geotextile fabric to knock mud off vehicle tires as they leave the site, preventing sediment tracking onto roads.
CSM CSM Erosion & Sediment Control 1
What is the primary purpose of a silt fence installed at a construction site?