AR STW Stormwater Systems
Contractor Exam Questions And
Correct Answers (Verified Answers)
Plus Rationale2026 Q&A| Instant
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What is the primary purpose of a stormwater detention basin?
A. To provide irrigation water
B. To treat sewage
C. To temporarily store stormwater and reduce peak discharge
D. To generate hydroelectric power
Rationale: A detention basin temporarily holds stormwater to control peak
flow rates, preventing downstream flooding.
1. Which material is most commonly used for stormwater pipes?
A. Wood
B. PVC
C. Aluminum
D. Glass
Rationale: PVC is lightweight, durable, and resistant to corrosion,
making it ideal for stormwater systems.
2. What is the main difference between a storm sewer and a sanitary
sewer?
A. Storm sewers carry wastewater, sanitary sewers carry rainwater
B. Storm sewers carry runoff water, sanitary sewers carry
wastewater
C. Storm sewers are always above ground, sanitary sewers are
underground
D. There is no difference
, Rationale: Storm sewers are designed to carry rainwater or runoff,
while sanitary sewers handle household and industrial wastewater.
3. What is the typical slope required for a gravity stormwater pipe?
A. 0.01%
B. 0.5%
C. 1%–2%
D. 10%
Rationale: A slope of 1–2% ensures adequate flow velocity to prevent
sediment deposition without causing excessive erosion.
4. Which of the following best describes a catch basin?
A. A structure for sewage treatment
B. A stormwater inlet that collects runoff and traps debris
C. A type of retention pond
D. A water treatment chemical
Rationale: Catch basins collect runoff from streets and trap debris
before water enters the storm sewer system.
5. What is the function of a stormwater outfall?
A. To store water
B. To discharge stormwater from the system into a receiving water
body
C. To filter pollutants
D. To increase water pressure
Rationale: Outfalls direct collected stormwater safely into rivers,
lakes, or other drainage areas.
6. Which device is used to prevent sediment from entering storm drains
during construction?
A. Manhole
B. Culvert
C. Silt fence
D. Retention basin
Rationale: Silt fences act as temporary barriers to trap sediment on
construction sites, protecting stormwater systems.
7. What is the main cause of stormwater pollution?
A. Groundwater infiltration
B. Industrial cooling
C. Runoff carrying debris, oil, and chemicals
D. Evaporation
, Rationale: Stormwater runoff can pick up pollutants from streets,
lawns, and construction sites, contaminating water bodies.
8. Which type of stormwater management structure is designed to
infiltrate water into the ground?
A. Detention basin
B. Infiltration basin
C. Sediment trap
D. Catch basin
Rationale: Infiltration basins allow stormwater to percolate into the
soil, replenishing groundwater.
9. What is the minimum freeboard typically required for a stormwater
pond?
A. 6 inches
B. 12 inches
C. 18 inches
D. 36 inches
Rationale: Freeboard is the vertical distance from the water surface to
the top of the pond; 18 inches is standard to prevent overflow during
storms.
10. What is the purpose of an energy dissipation structure at the end
of a stormwater outfall?
A. To increase water speed
B. To store water for irrigation
C. To reduce erosion by dissipating flow energy
D. To filter chemicals
Rationale: Energy dissipation prevents erosion of soil or concrete
where stormwater exits a system.
11. Which of the following is a common method to control sediment
in stormwater systems?
A. Chlorination
B. Filtration with sand
C. Sedimentation basins
D. Aeration
Rationale: Sedimentation basins slow down water, allowing suspended
solids to settle before discharge.
12. What is the recommended spacing for catch basins along a
typical residential street?
Contractor Exam Questions And
Correct Answers (Verified Answers)
Plus Rationale2026 Q&A| Instant
Download Pdf
What is the primary purpose of a stormwater detention basin?
A. To provide irrigation water
B. To treat sewage
C. To temporarily store stormwater and reduce peak discharge
D. To generate hydroelectric power
Rationale: A detention basin temporarily holds stormwater to control peak
flow rates, preventing downstream flooding.
1. Which material is most commonly used for stormwater pipes?
A. Wood
B. PVC
C. Aluminum
D. Glass
Rationale: PVC is lightweight, durable, and resistant to corrosion,
making it ideal for stormwater systems.
2. What is the main difference between a storm sewer and a sanitary
sewer?
A. Storm sewers carry wastewater, sanitary sewers carry rainwater
B. Storm sewers carry runoff water, sanitary sewers carry
wastewater
C. Storm sewers are always above ground, sanitary sewers are
underground
D. There is no difference
, Rationale: Storm sewers are designed to carry rainwater or runoff,
while sanitary sewers handle household and industrial wastewater.
3. What is the typical slope required for a gravity stormwater pipe?
A. 0.01%
B. 0.5%
C. 1%–2%
D. 10%
Rationale: A slope of 1–2% ensures adequate flow velocity to prevent
sediment deposition without causing excessive erosion.
4. Which of the following best describes a catch basin?
A. A structure for sewage treatment
B. A stormwater inlet that collects runoff and traps debris
C. A type of retention pond
D. A water treatment chemical
Rationale: Catch basins collect runoff from streets and trap debris
before water enters the storm sewer system.
5. What is the function of a stormwater outfall?
A. To store water
B. To discharge stormwater from the system into a receiving water
body
C. To filter pollutants
D. To increase water pressure
Rationale: Outfalls direct collected stormwater safely into rivers,
lakes, or other drainage areas.
6. Which device is used to prevent sediment from entering storm drains
during construction?
A. Manhole
B. Culvert
C. Silt fence
D. Retention basin
Rationale: Silt fences act as temporary barriers to trap sediment on
construction sites, protecting stormwater systems.
7. What is the main cause of stormwater pollution?
A. Groundwater infiltration
B. Industrial cooling
C. Runoff carrying debris, oil, and chemicals
D. Evaporation
, Rationale: Stormwater runoff can pick up pollutants from streets,
lawns, and construction sites, contaminating water bodies.
8. Which type of stormwater management structure is designed to
infiltrate water into the ground?
A. Detention basin
B. Infiltration basin
C. Sediment trap
D. Catch basin
Rationale: Infiltration basins allow stormwater to percolate into the
soil, replenishing groundwater.
9. What is the minimum freeboard typically required for a stormwater
pond?
A. 6 inches
B. 12 inches
C. 18 inches
D. 36 inches
Rationale: Freeboard is the vertical distance from the water surface to
the top of the pond; 18 inches is standard to prevent overflow during
storms.
10. What is the purpose of an energy dissipation structure at the end
of a stormwater outfall?
A. To increase water speed
B. To store water for irrigation
C. To reduce erosion by dissipating flow energy
D. To filter chemicals
Rationale: Energy dissipation prevents erosion of soil or concrete
where stormwater exits a system.
11. Which of the following is a common method to control sediment
in stormwater systems?
A. Chlorination
B. Filtration with sand
C. Sedimentation basins
D. Aeration
Rationale: Sedimentation basins slow down water, allowing suspended
solids to settle before discharge.
12. What is the recommended spacing for catch basins along a
typical residential street?
