CWEA WASTEWATER COLLECTION
SYSTEM GRADE 1 CERTIFICATION
EXAM PREP COMPLETE 150 FIELD
VERIFIED QUESTIONS WITH DETAILED
CORRECT ANSWERS AND RATIONALES
GRADE A+ COMPREHENSIVE
EVALUATION FILE | INSTANT
DOWNLOAD
1. What is the primary purpose of a wastewater collection system?
A) To treat industrial toxic waste down to drinking water standards
B) To safely collect and convey wastewater to a treatment facility
C) To store stormwater for long-term agricultural irrigation use
D) To separate oil and grease at the commercial source completely
Correct Answer: B
Rationale: The foundational purpose of any wastewater
collection system is to gather municipal sewage and transport it
efficiently and safely to a treatment plant while protecting public
health and preventing environmental contamination.
2. Which of the following parameters represents a typical minimum
scouring velocity required in a gravity sanitary sewer line to
prevent solids from settling?
A) 0.5 feet per second (fps)
B) 1.0 feet per second (fps)
C) 2.0 feet per second (fps)
D) 5.0 feet per second (fps)
Correct Answer: C
Rationale: Industry standards and regulatory guidelines
generally establish a minimum velocity of 2.0 feet per second
(fps) for gravity sewer designs. This scouring velocity is critical to
ensure that suspended organic and inorganic solids remain in
motion and do not deposit on the pipe invert.
,3. While performing routine maintenance, a collection system
operator notices a strong odor of rotten eggs coming from a
manhole. This gas is most likely:
A) Carbon monoxide (CO)
B) Hydrogen sulfide (H2S)
C) Methane (CH4)
D) Sulfur dioxide (SO2)
Correct Answer: B
Rationale: Hydrogen sulfide gas (H2S) is generated by the
anaerobic decomposition of sulfur compounds in stagnant
wastewater. It is easily recognized in low concentrations by its
characteristic "rotten egg" smell and poses severe toxic, explosive,
and corrosive hazards.
4. Which atmospheric hazard in a confined space is classified as an
asymptomatic asphyxiant and is highly flammable, lighter than air,
but lacks any natural odor?
A) Hydrogen sulfide
B) Methane
C) Carbon dioxide
D) Nitrogen dioxide
Correct Answer: B
Rationale: Methane (CH4) is a byproduct of anaerobic
decomposition in collection networks. It is a colorless, odorless,
highly flammable gas that can displace oxygen in enclosed
spaces, leading to physical asphyxiation.
5. According to OSHA standards, what is the minimum permissible
oxygen concentration required for safe entry into a permit-
required confined space without supplied-air respirators?
A) 16.0%
B) 19.5%
C) 21.0%
D) 23.5%
Correct Answer: B
Rationale: OSHA defines an oxygen-deficient atmosphere as
any environment containing less than 19.5% oxygen by volume.
Safe oxygen levels for entries must range between 19.5% and
23.5%.
,6. What is the main structural function of a drop manhole
configuration in a gravity sewer system?
A) To increase the overall flow velocity of upstream sewer
segments
B) To prevent the excessive erosion of the manhole invert due to
vertical drops
C) To allow maintenance personnel a safer entry route into deep
trench lines
D) To trap heavy silts and gravel before they enter down-gradient
trunk lines
Correct Answer: B
Rationale: Drop manholes are constructed when an incoming
sewer pipe enters more than 24 inches above the outgoing invert.
The internal or external drop stack directs flow smoothly to the
bottom, mitigating structural erosion, turbulence, and the release
of toxic H2S gas.
7. Which pipeline cleaning method relies on high-velocity water jets
to dislodge roots, emulsify grease, and flush debris down the line?
A) Power rodding
B) Hydro-jetting (high-velocity cleaner)
C) Sewer balling
D) Bucket machine dragging
Correct Answer: B
Rationale: Hydro-jetters use high-pressure pumps to force
water through a specialized nozzle. The forward-facing jets break
up obstructions while rear-facing jets propel the hose forward
and drag loose debris back toward the manhole for removal.
8. An operator needs to locate a buried metallic pipe using an
electronic pipe locator. This instrument operates primarily on what
physical principle?
A) Acoustic wave attenuation
B) Electromagnetic induction
C) Hydrostatic pressure reflection
D) Gamma-ray backscattering
Correct Answer: B
Rationale: Electronic pipe locators use an electromagnetic
transmitter to apply a signal to the metallic utility line, which is
, then tracked above-ground using a receiver tuned to that specific
frequency.
9. What type of pump is most commonly utilized in small wastewater
lift stations because it can handle significant solids without
clogging?
A) Multistage centrifugal turbine pump
B) Submersible non-clog centrifugal pump
C) Rotary gear positive displacement pump
D) Axial-flow propeller pump
Correct Answer: B
Rationale: Submersible non-clog centrifugal pumps feature
specially designed open or recessed impellers with wide clear
passages. This allows them to pass large solids, rags, and stringy
materials common in domestic sewage.
10. What does the term "Infiltration" specifically refer to in a
collection network?
A) Stormwater entering the system directly through holes in
manhole covers
B) Groundwater entering the sewer system through cracked pipes,
joints, and root intrusions
C) Industrial wastewater discharges that exceed localized volume
permissions
D) Rainwater entering via illegal residential roof downspout
connections
Correct Answer: B
Rationale: Infiltration is defined as groundwater that enters
the collection network through structural defects below the water
table, such as fractured pipes, faulty joints, or damaged manhole
walls. Entry through surface openings is classified as Inflow.
11. An operator is preparing to enter a confined space. What is the
correct sequence for checking atmospheric hazards using a multi-
gas monitor?
A) Combustible gases, toxic gases, oxygen content
B) Toxic gases, oxygen content, combustible gases
C) Oxygen content, combustible gases, toxic gases
D) Carbon monoxide, methane, hydrogen sulfide
Correct Answer: C
SYSTEM GRADE 1 CERTIFICATION
EXAM PREP COMPLETE 150 FIELD
VERIFIED QUESTIONS WITH DETAILED
CORRECT ANSWERS AND RATIONALES
GRADE A+ COMPREHENSIVE
EVALUATION FILE | INSTANT
DOWNLOAD
1. What is the primary purpose of a wastewater collection system?
A) To treat industrial toxic waste down to drinking water standards
B) To safely collect and convey wastewater to a treatment facility
C) To store stormwater for long-term agricultural irrigation use
D) To separate oil and grease at the commercial source completely
Correct Answer: B
Rationale: The foundational purpose of any wastewater
collection system is to gather municipal sewage and transport it
efficiently and safely to a treatment plant while protecting public
health and preventing environmental contamination.
2. Which of the following parameters represents a typical minimum
scouring velocity required in a gravity sanitary sewer line to
prevent solids from settling?
A) 0.5 feet per second (fps)
B) 1.0 feet per second (fps)
C) 2.0 feet per second (fps)
D) 5.0 feet per second (fps)
Correct Answer: C
Rationale: Industry standards and regulatory guidelines
generally establish a minimum velocity of 2.0 feet per second
(fps) for gravity sewer designs. This scouring velocity is critical to
ensure that suspended organic and inorganic solids remain in
motion and do not deposit on the pipe invert.
,3. While performing routine maintenance, a collection system
operator notices a strong odor of rotten eggs coming from a
manhole. This gas is most likely:
A) Carbon monoxide (CO)
B) Hydrogen sulfide (H2S)
C) Methane (CH4)
D) Sulfur dioxide (SO2)
Correct Answer: B
Rationale: Hydrogen sulfide gas (H2S) is generated by the
anaerobic decomposition of sulfur compounds in stagnant
wastewater. It is easily recognized in low concentrations by its
characteristic "rotten egg" smell and poses severe toxic, explosive,
and corrosive hazards.
4. Which atmospheric hazard in a confined space is classified as an
asymptomatic asphyxiant and is highly flammable, lighter than air,
but lacks any natural odor?
A) Hydrogen sulfide
B) Methane
C) Carbon dioxide
D) Nitrogen dioxide
Correct Answer: B
Rationale: Methane (CH4) is a byproduct of anaerobic
decomposition in collection networks. It is a colorless, odorless,
highly flammable gas that can displace oxygen in enclosed
spaces, leading to physical asphyxiation.
5. According to OSHA standards, what is the minimum permissible
oxygen concentration required for safe entry into a permit-
required confined space without supplied-air respirators?
A) 16.0%
B) 19.5%
C) 21.0%
D) 23.5%
Correct Answer: B
Rationale: OSHA defines an oxygen-deficient atmosphere as
any environment containing less than 19.5% oxygen by volume.
Safe oxygen levels for entries must range between 19.5% and
23.5%.
,6. What is the main structural function of a drop manhole
configuration in a gravity sewer system?
A) To increase the overall flow velocity of upstream sewer
segments
B) To prevent the excessive erosion of the manhole invert due to
vertical drops
C) To allow maintenance personnel a safer entry route into deep
trench lines
D) To trap heavy silts and gravel before they enter down-gradient
trunk lines
Correct Answer: B
Rationale: Drop manholes are constructed when an incoming
sewer pipe enters more than 24 inches above the outgoing invert.
The internal or external drop stack directs flow smoothly to the
bottom, mitigating structural erosion, turbulence, and the release
of toxic H2S gas.
7. Which pipeline cleaning method relies on high-velocity water jets
to dislodge roots, emulsify grease, and flush debris down the line?
A) Power rodding
B) Hydro-jetting (high-velocity cleaner)
C) Sewer balling
D) Bucket machine dragging
Correct Answer: B
Rationale: Hydro-jetters use high-pressure pumps to force
water through a specialized nozzle. The forward-facing jets break
up obstructions while rear-facing jets propel the hose forward
and drag loose debris back toward the manhole for removal.
8. An operator needs to locate a buried metallic pipe using an
electronic pipe locator. This instrument operates primarily on what
physical principle?
A) Acoustic wave attenuation
B) Electromagnetic induction
C) Hydrostatic pressure reflection
D) Gamma-ray backscattering
Correct Answer: B
Rationale: Electronic pipe locators use an electromagnetic
transmitter to apply a signal to the metallic utility line, which is
, then tracked above-ground using a receiver tuned to that specific
frequency.
9. What type of pump is most commonly utilized in small wastewater
lift stations because it can handle significant solids without
clogging?
A) Multistage centrifugal turbine pump
B) Submersible non-clog centrifugal pump
C) Rotary gear positive displacement pump
D) Axial-flow propeller pump
Correct Answer: B
Rationale: Submersible non-clog centrifugal pumps feature
specially designed open or recessed impellers with wide clear
passages. This allows them to pass large solids, rags, and stringy
materials common in domestic sewage.
10. What does the term "Infiltration" specifically refer to in a
collection network?
A) Stormwater entering the system directly through holes in
manhole covers
B) Groundwater entering the sewer system through cracked pipes,
joints, and root intrusions
C) Industrial wastewater discharges that exceed localized volume
permissions
D) Rainwater entering via illegal residential roof downspout
connections
Correct Answer: B
Rationale: Infiltration is defined as groundwater that enters
the collection network through structural defects below the water
table, such as fractured pipes, faulty joints, or damaged manhole
walls. Entry through surface openings is classified as Inflow.
11. An operator is preparing to enter a confined space. What is the
correct sequence for checking atmospheric hazards using a multi-
gas monitor?
A) Combustible gases, toxic gases, oxygen content
B) Toxic gases, oxygen content, combustible gases
C) Oxygen content, combustible gases, toxic gases
D) Carbon monoxide, methane, hydrogen sulfide
Correct Answer: C
