CO Stormwater Systems Contractor
Exam Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary purpose of a stormwater system?
A. To supply potable water
B. To manage and convey rainfall runoff
C. To treat sewage
D. To store drinking water
B. To manage and convey rainfall runoff
Rationale: Stormwater systems are designed to collect, transport, and
discharge rainfall runoff to prevent flooding and erosion.
2. Which type of pipe is most commonly used for stormwater drainage?
A. PVC
B. Copper
C. Galvanized steel
D. Asbestos cement
A. PVC
Rationale: PVC pipes are lightweight, corrosion-resistant, and easy to
install, making them ideal for stormwater systems.
3. What is the minimum slope recommended for a stormwater drainage
pipe to ensure proper flow?
A. 0.1%
B. 0.5%
C. 1%
D. 2%
C. 1%
Rationale: A minimum slope of 1% ensures that water flows
efficiently by gravity and prevents sediment buildup.
,4. What is the primary function of a catch basin in a stormwater system?
A. To treat wastewater
B. To collect sediment and debris
C. To store potable water
D. To pump water uphill
B. To collect sediment and debris
Rationale: Catch basins trap sediment and debris before water enters
the storm sewer system, preventing clogs.
5. Which stormwater component is used to slow down the flow of water
to prevent downstream flooding?
A. Manhole
B. Retention pond
C. Storm drain grate
D. Inlet pipe
B. Retention pond
Rationale: Retention ponds temporarily hold stormwater, releasing it
slowly to reduce peak flow and flooding risk.
6. What is the purpose of a stormwater manhole?
A. To filter pollutants
B. To provide access for inspection and maintenance
C. To store stormwater permanently
D. To supply water to buildings
B. To provide access for inspection and maintenance
Rationale: Manholes allow personnel to inspect, maintain, and clean
stormwater pipes safely.
7. What is the term for the impervious area that contributes runoff to a
stormwater system?
A. Drainage area
B. Watershed
C. Catchment area
D. Impermeable zone
C. Catchment area
Rationale: The catchment area is the surface area from which
stormwater runoff flows into the system.
8. Which design factor is crucial when sizing a stormwater pipe?
A. Water color
B. Peak flow rate
, C. Pipe material cost
D. Soil fertility
B. Peak flow rate
Rationale: Stormwater pipes must be sized to accommodate the
maximum expected flow during a design storm.
9. What type of stormwater system reduces runoff volume by promoting
infiltration into the soil?
A. Detention pond
B. Permeable pavement
C. Closed conduit
D. Open channel
B. Permeable pavement
Rationale: Permeable pavements allow water to infiltrate into the
ground, reducing runoff and recharging groundwater.
10. Which of the following is a best management practice (BMP) for
stormwater quality?
A. Sand filters
B. Open flame
C. Chlorination
D. Gravel excavation
A. Sand filters
Rationale: Sand filters remove sediments and pollutants from
stormwater before discharge, improving water quality.
11. What is the main purpose of a stormwater retention basin?
A. Permanent water storage
B. Temporary water storage for flood control
C. Wastewater treatment
D. Drinking water supply
B. Temporary water storage for flood control
Rationale: Retention basins temporarily store excess runoff,
controlling downstream flooding.
12. Which method is used to calculate stormwater runoff from a
catchment area?
A. Darcy’s law
B. Rational method
C. Manning’s equation
D. Bernoulli’s principle
Exam Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary purpose of a stormwater system?
A. To supply potable water
B. To manage and convey rainfall runoff
C. To treat sewage
D. To store drinking water
B. To manage and convey rainfall runoff
Rationale: Stormwater systems are designed to collect, transport, and
discharge rainfall runoff to prevent flooding and erosion.
2. Which type of pipe is most commonly used for stormwater drainage?
A. PVC
B. Copper
C. Galvanized steel
D. Asbestos cement
A. PVC
Rationale: PVC pipes are lightweight, corrosion-resistant, and easy to
install, making them ideal for stormwater systems.
3. What is the minimum slope recommended for a stormwater drainage
pipe to ensure proper flow?
A. 0.1%
B. 0.5%
C. 1%
D. 2%
C. 1%
Rationale: A minimum slope of 1% ensures that water flows
efficiently by gravity and prevents sediment buildup.
,4. What is the primary function of a catch basin in a stormwater system?
A. To treat wastewater
B. To collect sediment and debris
C. To store potable water
D. To pump water uphill
B. To collect sediment and debris
Rationale: Catch basins trap sediment and debris before water enters
the storm sewer system, preventing clogs.
5. Which stormwater component is used to slow down the flow of water
to prevent downstream flooding?
A. Manhole
B. Retention pond
C. Storm drain grate
D. Inlet pipe
B. Retention pond
Rationale: Retention ponds temporarily hold stormwater, releasing it
slowly to reduce peak flow and flooding risk.
6. What is the purpose of a stormwater manhole?
A. To filter pollutants
B. To provide access for inspection and maintenance
C. To store stormwater permanently
D. To supply water to buildings
B. To provide access for inspection and maintenance
Rationale: Manholes allow personnel to inspect, maintain, and clean
stormwater pipes safely.
7. What is the term for the impervious area that contributes runoff to a
stormwater system?
A. Drainage area
B. Watershed
C. Catchment area
D. Impermeable zone
C. Catchment area
Rationale: The catchment area is the surface area from which
stormwater runoff flows into the system.
8. Which design factor is crucial when sizing a stormwater pipe?
A. Water color
B. Peak flow rate
, C. Pipe material cost
D. Soil fertility
B. Peak flow rate
Rationale: Stormwater pipes must be sized to accommodate the
maximum expected flow during a design storm.
9. What type of stormwater system reduces runoff volume by promoting
infiltration into the soil?
A. Detention pond
B. Permeable pavement
C. Closed conduit
D. Open channel
B. Permeable pavement
Rationale: Permeable pavements allow water to infiltrate into the
ground, reducing runoff and recharging groundwater.
10. Which of the following is a best management practice (BMP) for
stormwater quality?
A. Sand filters
B. Open flame
C. Chlorination
D. Gravel excavation
A. Sand filters
Rationale: Sand filters remove sediments and pollutants from
stormwater before discharge, improving water quality.
11. What is the main purpose of a stormwater retention basin?
A. Permanent water storage
B. Temporary water storage for flood control
C. Wastewater treatment
D. Drinking water supply
B. Temporary water storage for flood control
Rationale: Retention basins temporarily store excess runoff,
controlling downstream flooding.
12. Which method is used to calculate stormwater runoff from a
catchment area?
A. Darcy’s law
B. Rational method
C. Manning’s equation
D. Bernoulli’s principle
