CLA CLA Grading & Drainage 1 — Questions and Answers
Question 1: What is the minimum recommended slope for lawn areas to ensure positive drainage away from structures?
- 1%
- 2% (Correct answer)
- 5%
- 10%
Correct answer: 2%
A minimum 2% slope is generally recommended for lawn areas to direct stormwater away from buildings.
Question 2: A spot elevation of 102.50 is shown at the top of a swale and 100.00 at the bottom over a 50-foot run. What is the slope percentage?
- 2.5%
- 5% (Correct answer)
- 10%
- 50%
Correct answer: 5%
Slope % = (rise/run) × 100 = (2.50/50) × 100 = 5%.
Question 3: Which type of inlet is typically used at the low point of a parking lot to collect surface runoff?
- Yard inlet
- Curb inlet
- Trench drain
- Catch basin (Correct answer)
Correct answer: Catch basin
Catch basins are standard at low points in paved areas because they collect surface water and trap sediment below the outlet pipe.
Question 4: What grading technique uses a series of flat terraces separated by steep risers to manage slopes on hillsides?
- Cut and fill
- Bench grading (Correct answer)
- Swale routing
- Berm construction
Correct answer: Bench grading
Bench grading creates level planting terraces on steep slopes, reducing erosion and allowing access.
Question 5: On a grading plan, a dashed contour line typically indicates:
- Existing grade
- Proposed grade (Correct answer)
- Limit of work
- Drainage swale
Correct answer: Proposed grade
Dashed contour lines represent proposed (finished) grade, while solid lines represent existing grade.
Question 6: What is the primary purpose of a drainage swale in landscape grading?
- Retain stormwater on site
- Convey surface runoff in a controlled channel (Correct answer)
- Increase infiltration only
- Separate planting zones
Correct answer: Convey surface runoff in a controlled channel
A drainage swale is a shallow, vegetated channel designed to move surface runoff from one area to another while reducing velocity.
CLA CLA Grading & Drainage 1
What is the minimum recommended slope for lawn areas to ensure positive drainage away from structures?