Arizona AZ L-83 Stormwater
Systems Contractor Practice
Exam | Questions, Verified
Answers & Detailed Rationales |
Complete Contractor License
Exam Prep Study Guide |
Updated 2026
1. What is the primary purpose of a stormwater
drainage system?
A. To increase groundwater contamination
B. To safely collect, convey, control, and discharge runoff
C. To eliminate all rainfall from a property
D. To prevent groundwater recharge
Correct answer: To safely collect, convey, control, and
discharge runoff
Rationale: A stormwater system is designed to manage
runoff so that water is safely collected, transported,
controlled, detained or retained when necessary, and
discharged without causing unacceptable flooding,
erosion, or property damage.
2. What happens to runoff when impervious surface area
increases?
A. Runoff generally decreases
B. Runoff generally increases
C. Infiltration always increases
D. Evaporation becomes the only significant process
Correct answer: Runoff generally increases
,Rationale: Impervious surfaces such as roofs, pavement,
and concrete prevent water from infiltrating into the
soil, increasing the volume and often the peak rate of
stormwater runoff.
3. Which surface is generally most pervious?
A. Concrete pavement
B. Asphalt pavement
C. Compacted clay
D. Undisturbed sandy soil
Correct answer: Undisturbed sandy soil
Rationale: Sandy soils generally have relatively large
pore spaces and can allow substantial infiltration
compared with pavement or heavily compacted soils.
4. What is infiltration?
A. Movement of water from soil into the atmosphere
B. Movement of water from the ground into a pipe
C. Movement of water from the surface into the soil
D. Movement of sediment through a culvert
Correct answer: Movement of water from the surface
into the soil
Rationale: Infiltration is the process by which water
enters the soil surface. It is an important component of
groundwater recharge and stormwater management.
5. What is the watershed or drainage basin of a point?
A. Only the area immediately surrounding a drain
B. The area that contributes runoff to that point
C. The area below the groundwater table
D. The area occupied by a detention basin only
,Correct answer: The area that contributes runoff to that
point
Rationale: A watershed is the land area from which
precipitation drains toward a common outlet or
drainage point.
6. What is the rational method commonly used to
estimate?
A. Soil density
B. Peak stormwater runoff rate
C. Pipe material strength
D. Groundwater elevation
Correct answer: Peak stormwater runoff rate
Rationale: The Rational Method is commonly used for
estimating peak runoff from relatively small drainage
areas using rainfall intensity, drainage area, and runoff
coefficient.
7. In the Rational Method, what does the runoff
coefficient represent?
A. Pipe roughness
B. The fraction of rainfall that becomes runoff
C. Soil temperature
D. Pipe diameter
Correct answer: The fraction of rainfall that becomes
runoff
Rationale: The runoff coefficient represents the portion
of rainfall that contributes to surface runoff rather than
infiltration, evaporation, or other losses.
8. Which condition generally produces the greatest
runoff coefficient?
, A. Forested soil
B. Grass-covered soil
C. Concrete pavement
D. Undisturbed sandy ground
Correct answer: Concrete pavement
Rationale: Concrete is highly impervious, so a large
percentage of rainfall becomes surface runoff rather
than infiltrating into the ground.
9. What is peak discharge?
A. The total volume of rainfall during a storm
B. The highest flow rate occurring during a runoff event
C. The lowest groundwater elevation
D. The amount of sediment in a basin
Correct answer: The highest flow rate occurring during a
runoff event
Rationale: Peak discharge is the maximum rate at which
water flows through a drainage point during a storm
event.
10. What is the primary purpose of a storm drain inlet?
A. To discharge wastewater
B. To collect surface runoff and direct it into the drainage
system
C. To increase pavement strength
D. To prevent all groundwater movement
Correct answer: To collect surface runoff and direct it
into the drainage system
Rationale: Inlets capture runoff from streets, parking
lots, yards, and other surfaces and transfer the water
into pipes or other conveyance facilities.
Systems Contractor Practice
Exam | Questions, Verified
Answers & Detailed Rationales |
Complete Contractor License
Exam Prep Study Guide |
Updated 2026
1. What is the primary purpose of a stormwater
drainage system?
A. To increase groundwater contamination
B. To safely collect, convey, control, and discharge runoff
C. To eliminate all rainfall from a property
D. To prevent groundwater recharge
Correct answer: To safely collect, convey, control, and
discharge runoff
Rationale: A stormwater system is designed to manage
runoff so that water is safely collected, transported,
controlled, detained or retained when necessary, and
discharged without causing unacceptable flooding,
erosion, or property damage.
2. What happens to runoff when impervious surface area
increases?
A. Runoff generally decreases
B. Runoff generally increases
C. Infiltration always increases
D. Evaporation becomes the only significant process
Correct answer: Runoff generally increases
,Rationale: Impervious surfaces such as roofs, pavement,
and concrete prevent water from infiltrating into the
soil, increasing the volume and often the peak rate of
stormwater runoff.
3. Which surface is generally most pervious?
A. Concrete pavement
B. Asphalt pavement
C. Compacted clay
D. Undisturbed sandy soil
Correct answer: Undisturbed sandy soil
Rationale: Sandy soils generally have relatively large
pore spaces and can allow substantial infiltration
compared with pavement or heavily compacted soils.
4. What is infiltration?
A. Movement of water from soil into the atmosphere
B. Movement of water from the ground into a pipe
C. Movement of water from the surface into the soil
D. Movement of sediment through a culvert
Correct answer: Movement of water from the surface
into the soil
Rationale: Infiltration is the process by which water
enters the soil surface. It is an important component of
groundwater recharge and stormwater management.
5. What is the watershed or drainage basin of a point?
A. Only the area immediately surrounding a drain
B. The area that contributes runoff to that point
C. The area below the groundwater table
D. The area occupied by a detention basin only
,Correct answer: The area that contributes runoff to that
point
Rationale: A watershed is the land area from which
precipitation drains toward a common outlet or
drainage point.
6. What is the rational method commonly used to
estimate?
A. Soil density
B. Peak stormwater runoff rate
C. Pipe material strength
D. Groundwater elevation
Correct answer: Peak stormwater runoff rate
Rationale: The Rational Method is commonly used for
estimating peak runoff from relatively small drainage
areas using rainfall intensity, drainage area, and runoff
coefficient.
7. In the Rational Method, what does the runoff
coefficient represent?
A. Pipe roughness
B. The fraction of rainfall that becomes runoff
C. Soil temperature
D. Pipe diameter
Correct answer: The fraction of rainfall that becomes
runoff
Rationale: The runoff coefficient represents the portion
of rainfall that contributes to surface runoff rather than
infiltration, evaporation, or other losses.
8. Which condition generally produces the greatest
runoff coefficient?
, A. Forested soil
B. Grass-covered soil
C. Concrete pavement
D. Undisturbed sandy ground
Correct answer: Concrete pavement
Rationale: Concrete is highly impervious, so a large
percentage of rainfall becomes surface runoff rather
than infiltrating into the ground.
9. What is peak discharge?
A. The total volume of rainfall during a storm
B. The highest flow rate occurring during a runoff event
C. The lowest groundwater elevation
D. The amount of sediment in a basin
Correct answer: The highest flow rate occurring during a
runoff event
Rationale: Peak discharge is the maximum rate at which
water flows through a drainage point during a storm
event.
10. What is the primary purpose of a storm drain inlet?
A. To discharge wastewater
B. To collect surface runoff and direct it into the drainage
system
C. To increase pavement strength
D. To prevent all groundwater movement
Correct answer: To collect surface runoff and direct it
into the drainage system
Rationale: Inlets capture runoff from streets, parking
lots, yards, and other surfaces and transfer the water
into pipes or other conveyance facilities.
