CO Grading & Drainage Contractor
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the primary purpose of grading on a construction site?
A. To improve aesthetic appeal
B. To prevent soil erosion
C. To provide proper drainage
D. To reduce construction costs
C. To provide proper drainage
Rationale: Proper grading ensures that water flows away from structures,
preventing flooding and structural damage.
2. What type of soil has the highest permeability?
A. Clay
B. Silt
C. Sand
D. Loam
C. Sand
Rationale: Sand particles are large and allow water to pass through
quickly, making it highly permeable.
3. Which slope is recommended for surface drainage away from a
building?
A. 1%
B. 2%
C. 5%
D. 10%
B. 2%
,Rationale: A 2% slope (1/4 inch per foot) is commonly recommended to
ensure water drains away from foundations without causing erosion.
4. What is the main function of a swale?
A. Decorative landscaping
B. To channel water away from an area
C. To compact soil
D. To stabilize slopes
B. To channel water away from an area
Rationale: Swales are shallow, vegetated channels designed to convey
water safely while reducing erosion.
5. Which piece of equipment is commonly used for fine grading?
A. Bulldozer
B. Backhoe
C. Motor grader
D. Compactor
C. Motor grader
Rationale: A motor grader is designed for precision grading to achieve
smooth slopes and proper drainage.
6. What is the main risk of insufficient grading around a building?
A. Soil compaction
B. Water infiltration into foundations
C. Reduced sunlight
D. Poor landscaping appearance
B. Water infiltration into foundations
Rationale: Poor grading can lead to water pooling near foundations,
causing structural damage and mold growth.
7. How should stormwater be managed on a sloped site?
A. Allow it to flow freely
B. Divert it to low areas near the building
C. Direct it into a controlled drainage system
D. Capture it in depressions near trees
C. Direct it into a controlled drainage system
Rationale: Controlled drainage systems, like culverts or storm drains,
prevent erosion and property damage.
, 8. Which soil property most affects its drainage capability?
A. Color
B. Particle size
C. pH
D. Organic content
B. Particle size
Rationale: Coarse particles like sand allow water to drain quickly, whereas
fine particles like clay slow drainage.
9. What is the purpose of a catch basin?
A. Store potable water
B. Collect surface water runoff and debris
C. Provide irrigation
D. Stabilize soil on slopes
B. Collect surface water runoff and debris
Rationale: Catch basins capture stormwater and sediment, preventing
blockages in drainage pipes.
10. Which type of drainage system is most suitable for a large parking
lot?
A. French drain
B. Surface drain inlets and pipes
C. Sump pit
D. Berms
B. Surface drain inlets and pipes
Rationale: Surface drains efficiently convey large volumes of water from
impervious areas like parking lots.
11. What is the minimum slope recommended for a French drain?
A. 0.5%
B. 1%
C. 2%
D. 5%
B. 1%
Rationale: A slope of at least 1% ensures water flows through the drain
while avoiding stagnation.
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the primary purpose of grading on a construction site?
A. To improve aesthetic appeal
B. To prevent soil erosion
C. To provide proper drainage
D. To reduce construction costs
C. To provide proper drainage
Rationale: Proper grading ensures that water flows away from structures,
preventing flooding and structural damage.
2. What type of soil has the highest permeability?
A. Clay
B. Silt
C. Sand
D. Loam
C. Sand
Rationale: Sand particles are large and allow water to pass through
quickly, making it highly permeable.
3. Which slope is recommended for surface drainage away from a
building?
A. 1%
B. 2%
C. 5%
D. 10%
B. 2%
,Rationale: A 2% slope (1/4 inch per foot) is commonly recommended to
ensure water drains away from foundations without causing erosion.
4. What is the main function of a swale?
A. Decorative landscaping
B. To channel water away from an area
C. To compact soil
D. To stabilize slopes
B. To channel water away from an area
Rationale: Swales are shallow, vegetated channels designed to convey
water safely while reducing erosion.
5. Which piece of equipment is commonly used for fine grading?
A. Bulldozer
B. Backhoe
C. Motor grader
D. Compactor
C. Motor grader
Rationale: A motor grader is designed for precision grading to achieve
smooth slopes and proper drainage.
6. What is the main risk of insufficient grading around a building?
A. Soil compaction
B. Water infiltration into foundations
C. Reduced sunlight
D. Poor landscaping appearance
B. Water infiltration into foundations
Rationale: Poor grading can lead to water pooling near foundations,
causing structural damage and mold growth.
7. How should stormwater be managed on a sloped site?
A. Allow it to flow freely
B. Divert it to low areas near the building
C. Direct it into a controlled drainage system
D. Capture it in depressions near trees
C. Direct it into a controlled drainage system
Rationale: Controlled drainage systems, like culverts or storm drains,
prevent erosion and property damage.
, 8. Which soil property most affects its drainage capability?
A. Color
B. Particle size
C. pH
D. Organic content
B. Particle size
Rationale: Coarse particles like sand allow water to drain quickly, whereas
fine particles like clay slow drainage.
9. What is the purpose of a catch basin?
A. Store potable water
B. Collect surface water runoff and debris
C. Provide irrigation
D. Stabilize soil on slopes
B. Collect surface water runoff and debris
Rationale: Catch basins capture stormwater and sediment, preventing
blockages in drainage pipes.
10. Which type of drainage system is most suitable for a large parking
lot?
A. French drain
B. Surface drain inlets and pipes
C. Sump pit
D. Berms
B. Surface drain inlets and pipes
Rationale: Surface drains efficiently convey large volumes of water from
impervious areas like parking lots.
11. What is the minimum slope recommended for a French drain?
A. 0.5%
B. 1%
C. 2%
D. 5%
B. 1%
Rationale: A slope of at least 1% ensures water flows through the drain
while avoiding stagnation.
