CO Stormwater Systems Contractor Exam
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
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1. What is the primary purpose of a stormwater drainage system?
A. To increase groundwater salinity
B. To prevent all rainfall from reaching the ground
C. To collect, convey, manage, and discharge stormwater safely
D. To eliminate the need for erosion control
Rationale: Stormwater systems are designed to manage
runoff generated by rainfall and snowmelt. Proper systems
collect and convey runoff while reducing flooding, erosion,
property damage, and impacts to receiving waters.
2. Which factor most directly affects the amount of stormwater
runoff generated from a developed site?
,A. Soil color
B. The percentage of impervious surface
C. Building interior temperature
D. Type of landscaping furniture
Rationale: Impervious surfaces such as roofs, pavement, and
concrete prevent infiltration and generally increase the
volume and rate of runoff. Increasing impervious coverage
therefore has a major effect on stormwater design.
3. What is infiltration?
A. The movement of water through an enclosed pipe
B. The evaporation of water from pavement
C. The movement of water from the ground surface into the soil
D. The discharge of water into a storm sewer
Rationale: Infiltration occurs when water enters and moves
through the soil. It is an important component of stormwater
management because it can reduce surface runoff and help
replenish groundwater.
4. Which condition generally produces the greatest stormwater
runoff?
,A. Flat vegetated soil with high infiltration capacity
B. Forested land with undisturbed soil
C. Paved surfaces with little infiltration
D. Deep mulch over loose soil
Rationale: Pavement and other impervious surfaces greatly
restrict infiltration. Consequently, a larger proportion of
rainfall becomes surface runoff and reaches drainage facilities
quickly.
5. What is the Rational Method commonly used to estimate?
A. Structural steel capacity
B. Peak stormwater runoff rate
C. Soil pH
D. Pipe material cost
Rationale: The Rational Method is commonly used for
estimating peak runoff from relatively small drainage areas. It
relates rainfall intensity, drainage area, and a runoff
coefficient to estimate peak discharge.
6. In the Rational Method, what does the runoff coefficient
represent?
, A. Pipe roughness
B. Rainfall duration only
C. The proportion of rainfall that becomes runoff
D. The depth of a detention basin
Rationale: The runoff coefficient accounts for the
characteristics of the drainage area that influence how much
rainfall becomes direct runoff. Impervious areas generally
have higher runoff coefficients than permeable surfaces.
7. What generally happens to peak runoff when the drainage area
increases, assuming other factors remain constant?
A. It always becomes zero
B. Peak runoff generally increases
C. It becomes independent of rainfall
D. It decreases because pipes become longer
Rationale: A larger contributing drainage area generally
produces a greater volume of runoff and therefore a greater
peak discharge when other design conditions are comparable.
8. What is the time of concentration?
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
Download Pdf
1. What is the primary purpose of a stormwater drainage system?
A. To increase groundwater salinity
B. To prevent all rainfall from reaching the ground
C. To collect, convey, manage, and discharge stormwater safely
D. To eliminate the need for erosion control
Rationale: Stormwater systems are designed to manage
runoff generated by rainfall and snowmelt. Proper systems
collect and convey runoff while reducing flooding, erosion,
property damage, and impacts to receiving waters.
2. Which factor most directly affects the amount of stormwater
runoff generated from a developed site?
,A. Soil color
B. The percentage of impervious surface
C. Building interior temperature
D. Type of landscaping furniture
Rationale: Impervious surfaces such as roofs, pavement, and
concrete prevent infiltration and generally increase the
volume and rate of runoff. Increasing impervious coverage
therefore has a major effect on stormwater design.
3. What is infiltration?
A. The movement of water through an enclosed pipe
B. The evaporation of water from pavement
C. The movement of water from the ground surface into the soil
D. The discharge of water into a storm sewer
Rationale: Infiltration occurs when water enters and moves
through the soil. It is an important component of stormwater
management because it can reduce surface runoff and help
replenish groundwater.
4. Which condition generally produces the greatest stormwater
runoff?
,A. Flat vegetated soil with high infiltration capacity
B. Forested land with undisturbed soil
C. Paved surfaces with little infiltration
D. Deep mulch over loose soil
Rationale: Pavement and other impervious surfaces greatly
restrict infiltration. Consequently, a larger proportion of
rainfall becomes surface runoff and reaches drainage facilities
quickly.
5. What is the Rational Method commonly used to estimate?
A. Structural steel capacity
B. Peak stormwater runoff rate
C. Soil pH
D. Pipe material cost
Rationale: The Rational Method is commonly used for
estimating peak runoff from relatively small drainage areas. It
relates rainfall intensity, drainage area, and a runoff
coefficient to estimate peak discharge.
6. In the Rational Method, what does the runoff coefficient
represent?
, A. Pipe roughness
B. Rainfall duration only
C. The proportion of rainfall that becomes runoff
D. The depth of a detention basin
Rationale: The runoff coefficient accounts for the
characteristics of the drainage area that influence how much
rainfall becomes direct runoff. Impervious areas generally
have higher runoff coefficients than permeable surfaces.
7. What generally happens to peak runoff when the drainage area
increases, assuming other factors remain constant?
A. It always becomes zero
B. Peak runoff generally increases
C. It becomes independent of rainfall
D. It decreases because pipes become longer
Rationale: A larger contributing drainage area generally
produces a greater volume of runoff and therefore a greater
peak discharge when other design conditions are comparable.
8. What is the time of concentration?
