LARE LARE Grading and Earthwork 3 — Questions and Answers
Question 1: According to ADA guidelines, the maximum running slope for an accessible pedestrian walkway not classified as a ramp is:
- 2%
- 5% (Correct answer)
- 8.33%
- 12%
Correct answer: 5%
ADA standards allow a maximum 5% running slope (1:20) for accessible routes before the path is classified as a ramp requiring handrails and landings.
Question 2: A landscape architect is interpolating contours between two spot elevations. Point A is at elevation 98.0 and Point B is at elevation 104.0, with a horizontal distance of 30 feet between them. Where does the 100-foot contour cross the line AB?
- 5 feet from Point A
- 10 feet from Point A (Correct answer)
- 15 feet from Point A
- 20 feet from Point A
Correct answer: 10 feet from Point A
The 100-ft contour is 2 ft above Point A; total rise = 6 ft over 30 ft, so 2/6 × 30 = 10 feet from Point A.
Question 3: Which erosion control measure is best suited for stabilizing a 3:1 (H:V) slope immediately after grading when revegetation will take 6–8 weeks to establish?
- Silt fence at the slope base only
- Straw wattle along the contour
- Erosion control blanket (ECB) pinned to the slope (Correct answer)
- Concrete riprap
Correct answer: Erosion control blanket (ECB) pinned to the slope
Erosion control blankets protect the soil surface immediately, hold seed and moisture, and degrade naturally as vegetation establishes.
Question 4: A mass haul diagram is used in earthwork planning primarily to:
- Calculate total cut and fill volumes on a project
- Determine the economical haul distance and direction of soil movement (Correct answer)
- Identify the type of equipment needed for grading
- Estimate the swell and shrinkage factors of the soil
Correct answer: Determine the economical haul distance and direction of soil movement
A mass haul diagram shows cumulative earthwork along a project alignment, allowing the designer to identify the most economical direction and distance to haul excavated material.
Question 5: When grading near existing trees, which practice best protects tree roots from compaction damage?
- Slope grades away from the trunk at 2% minimum within the drip line
- Install a tree well inside the critical root zone (CRZ)
- Place 4–6 inches of wood chip mulch over the CRZ and restrict equipment access (Correct answer)
- Cut all surface roots before grading begins
Correct answer: Place 4–6 inches of wood chip mulch over the CRZ and restrict equipment access
Applying mulch over the critical root zone dissipates equipment pressure, retains moisture, and restricts access — the best practice for protecting roots during grading.
Question 6: A swale is designed with a 0.5% longitudinal slope, a 4-foot bottom width, and 3:1 side slopes. If the design flow depth is 1 foot, what is the cross-sectional flow area?
- 4.0 sq ft
- 5.0 sq ft
- 7.0 sq ft (Correct answer)
- 10.0 sq ft
Correct answer: 7.0 sq ft
Area = bottom width × depth + side slope factor × depth² = (4 × 1) + (3 × 1²) = 4 + 3 = 7.0 sq ft for a trapezoidal channel.
Question 7: On a grading plan, existing contours are shown as dashed lines and proposed contours as solid lines. A proposed contour that crosses an existing contour of the same elevation indicates:
- A design error — contours of the same elevation cannot cross
- A cut condition where grading removes existing material
- A fill condition where grading adds material above existing grade
- Either cut or fill depending on which contour is uphill (Correct answer)
Correct answer: Either cut or fill depending on which contour is uphill
When proposed and existing contours of the same elevation cross, it can indicate either cut or fill depending on the relative positions of adjacent higher and lower contours.
LARE LARE Grading and Earthwork 3
According to ADA guidelines, the maximum running slope for an accessible pedestrian walkway not classified as a ramp is: