CPESC Construction Site Controls 3 — Questions and Answers
Question 1: Which type of check dam material is most appropriate for installation in a high-velocity channel where rock is locally available?
- Straw wattles
- Rock riprap check dam (Correct answer)
- Silt fence check dam
- Compost sock
Correct answer: Rock riprap check dam
Rock riprap check dams are durable and resistant to scour in high-velocity flows, making them the preferred choice when local rock is available.
Question 2: Under the NPDES Construction General Permit, how frequently must a qualified person inspect a construction site's BMPs?
- Once per month
- At least every 14 days and within 24 hours after a 0.5-inch or greater rainfall event (Correct answer)
- Weekly regardless of rainfall
- Only after significant storm events exceeding 2 inches
Correct answer: At least every 14 days and within 24 hours after a 0.5-inch or greater rainfall event
The EPA's Construction General Permit requires inspections at least every 14 days and within 24 hours after any storm event of 0.5 inches or more.
Question 3: What is the main function of an outlet protection apron at a pipe culvert discharge?
- To filter sediment from pipe discharge
- To dissipate the energy of concentrated flow and prevent scour at the pipe outlet (Correct answer)
- To direct flow to a sediment basin
- To measure discharge velocity
Correct answer: To dissipate the energy of concentrated flow and prevent scour at the pipe outlet
Outlet protection aprons, typically made of rock riprap or concrete, absorb and dissipate the kinetic energy of pipe discharge to prevent channel erosion.
Question 4: A SWPPP requires that all areas of land disturbance be stabilized within 14 days of final grading. Which of the following does NOT meet this requirement?
- Seeding with a fast-germinating cover crop
- Applying erosion control blankets with seed
- Installing temporary mulch at 2-inch depth
- Rough grading the surface to a 2:1 slope and leaving bare (Correct answer)
Correct answer: Rough grading the surface to a 2:1 slope and leaving bare
Leaving bare, rough-graded soil without any stabilization measure does not meet the 14-day stabilization requirement under most NPDES permits.
Question 5: Which sediment control BMP is best suited for capturing sediment-laden runoff from a large disturbed area before it discharges off-site?
- Silt fence
- Sediment trap
- Sediment basin (Correct answer)
- Fiber rolls
Correct answer: Sediment basin
Sediment basins are designed to handle large drainage areas and provide sufficient retention time for sediment particles to settle before discharge.
Question 6: What is 'turbidity' in the context of construction site stormwater management?
- The total volume of runoff from a site during a storm event
- The cloudiness or haziness of water caused by suspended sediment particles (Correct answer)
- The pH level of stormwater discharge
- The velocity of stormwater in a drainage channel
Correct answer: The cloudiness or haziness of water caused by suspended sediment particles
Turbidity is a measure of water clarity caused by suspended solids; high turbidity from construction sites is a key indicator of sediment pollution.
Question 7: When is it most critical to install sediment controls on a construction site?
- After all grading activities are complete
- Before land disturbance begins or concurrently with initial clearing (Correct answer)
- Only during the wet season
- After the first rainfall event occurs on the site
Correct answer: Before land disturbance begins or concurrently with initial clearing
Sediment controls must be in place before or immediately concurrent with land disturbance to intercept sediment from the very first storm event.
CPESC Construction Site Controls 3
Which type of check dam material is most appropriate for installation in a high-velocity channel where rock is locally available?