TCEQ Wastewater Collection
System Operator Class III — Form A
Exam Questions and Correct
Answers with Detailed Rationales |
2026/2027 Edition | Exam Prep
Study Guide PDF
1. Which condition in a gravity wastewater collection system
most directly indicates that a sewer segment may be operating
under surcharge conditions?
A. The pipe has a smooth interior surface
B. The flow depth remains below one-half of the pipe diameter
C. The hydraulic grade line rises above the crown of the pipe
D. The upstream manhole has a watertight frame
Rationale: When the hydraulic grade line rises above the crown of
a closed conduit, the pipe is no longer operating as an open-
channel system throughout that section and may become
surcharged. Surcharge can result from downstream restrictions,
inadequate capacity, excessive inflow and infiltration, or other
hydraulic limitations.
2. A collection-system operator is evaluating a force main that
has experienced repeated odor complaints near a discharge
,manhole. Which condition is most likely contributing to the
problem?
A. Excessive dissolved oxygen in the force main
B. Long detention time under anaerobic conditions
C. Excessive pipe slope
D. High ultraviolet exposure
Rationale: Wastewater retained for extended periods in a force
main can become depleted of dissolved oxygen. Anaerobic
biological activity may then produce hydrogen sulfide and other
odor-causing compounds. Long force-main detention times are
therefore an important consideration when investigating recurring
odor problems.
3. What is the primary hydraulic purpose of maintaining an
appropriate minimum velocity in a gravity sewer?
A. To increase infiltration
B. To eliminate the need for manholes
C. To reduce the deposition of solids
D. To prevent all corrosion
Rationale: Adequate velocity helps transport suspended solids
through the collection system rather than allowing them to settle.
Insufficient velocity can contribute to sediment accumulation,
reduced capacity, odors, and blockages. Velocity requirements
must be considered along with pipe slope, diameter, flow
conditions, and applicable design criteria.
,4. During CCTV inspection, an operator observes a continuous
longitudinal crack along the crown of a sewer pipe. What should
be the operator's primary concern?
A. Normal biological growth
B. Minor discoloration
C. Structural deterioration that may progress to pipe failure
D. Excessive grease accumulation only
Rationale: A longitudinal crack can indicate structural distress. Its
significance depends on pipe material, crack width,
displacement, soil conditions, groundwater, and other factors.
The condition should be documented and evaluated rather than
dismissed as routine surface deterioration.
5. Which measurement is most useful when determining whether
infiltration is entering a collection system during dry-weather
conditions?
A. Chlorine residual
B. pH of drinking water
C. Flow monitoring during periods without rainfall
D. Sludge volume index
Rationale: Dry-weather flow monitoring can help identify
groundwater infiltration because sanitary wastewater generation
is relatively predictable while rainfall-related inflow is absent.
Elevated unexplained base flow can indicate groundwater
entering through defective joints, cracks, service connections, or
other pathways.
, 6. A manhole is located in an area subject to frequent flooding.
Which improvement would most directly reduce stormwater
inflow through the manhole?
A. Increasing downstream sewer slope
B. Installing a larger pump
C. Installing a watertight or appropriately sealed manhole
cover system
D. Increasing wastewater temperature
Rationale: Floodwater can enter through poorly sealed manhole
covers, frames, vents, and other openings. Properly sealing or
replacing defective components can reduce direct inflow. Any
modification must still provide appropriate access and ventilation
consistent with safety and regulatory requirements.
7. Which equation is commonly used to estimate flow velocity in
an open-channel portion of a gravity sewer?
A. Boyle's law
B. Darcy's law only
C. Manning's equation
D. Henry's law
Rationale: Manning's equation is widely used to estimate flow
velocity in open-channel flow based on hydraulic radius, slope,
and Manning's roughness coefficient. Collection-system
operators and engineers use it to evaluate hydraulic capacity and
flow conditions in gravity sewers.
8. A sewer has a diameter of 24 inches. What is its nominal
diameter in feet?
System Operator Class III — Form A
Exam Questions and Correct
Answers with Detailed Rationales |
2026/2027 Edition | Exam Prep
Study Guide PDF
1. Which condition in a gravity wastewater collection system
most directly indicates that a sewer segment may be operating
under surcharge conditions?
A. The pipe has a smooth interior surface
B. The flow depth remains below one-half of the pipe diameter
C. The hydraulic grade line rises above the crown of the pipe
D. The upstream manhole has a watertight frame
Rationale: When the hydraulic grade line rises above the crown of
a closed conduit, the pipe is no longer operating as an open-
channel system throughout that section and may become
surcharged. Surcharge can result from downstream restrictions,
inadequate capacity, excessive inflow and infiltration, or other
hydraulic limitations.
2. A collection-system operator is evaluating a force main that
has experienced repeated odor complaints near a discharge
,manhole. Which condition is most likely contributing to the
problem?
A. Excessive dissolved oxygen in the force main
B. Long detention time under anaerobic conditions
C. Excessive pipe slope
D. High ultraviolet exposure
Rationale: Wastewater retained for extended periods in a force
main can become depleted of dissolved oxygen. Anaerobic
biological activity may then produce hydrogen sulfide and other
odor-causing compounds. Long force-main detention times are
therefore an important consideration when investigating recurring
odor problems.
3. What is the primary hydraulic purpose of maintaining an
appropriate minimum velocity in a gravity sewer?
A. To increase infiltration
B. To eliminate the need for manholes
C. To reduce the deposition of solids
D. To prevent all corrosion
Rationale: Adequate velocity helps transport suspended solids
through the collection system rather than allowing them to settle.
Insufficient velocity can contribute to sediment accumulation,
reduced capacity, odors, and blockages. Velocity requirements
must be considered along with pipe slope, diameter, flow
conditions, and applicable design criteria.
,4. During CCTV inspection, an operator observes a continuous
longitudinal crack along the crown of a sewer pipe. What should
be the operator's primary concern?
A. Normal biological growth
B. Minor discoloration
C. Structural deterioration that may progress to pipe failure
D. Excessive grease accumulation only
Rationale: A longitudinal crack can indicate structural distress. Its
significance depends on pipe material, crack width,
displacement, soil conditions, groundwater, and other factors.
The condition should be documented and evaluated rather than
dismissed as routine surface deterioration.
5. Which measurement is most useful when determining whether
infiltration is entering a collection system during dry-weather
conditions?
A. Chlorine residual
B. pH of drinking water
C. Flow monitoring during periods without rainfall
D. Sludge volume index
Rationale: Dry-weather flow monitoring can help identify
groundwater infiltration because sanitary wastewater generation
is relatively predictable while rainfall-related inflow is absent.
Elevated unexplained base flow can indicate groundwater
entering through defective joints, cracks, service connections, or
other pathways.
, 6. A manhole is located in an area subject to frequent flooding.
Which improvement would most directly reduce stormwater
inflow through the manhole?
A. Increasing downstream sewer slope
B. Installing a larger pump
C. Installing a watertight or appropriately sealed manhole
cover system
D. Increasing wastewater temperature
Rationale: Floodwater can enter through poorly sealed manhole
covers, frames, vents, and other openings. Properly sealing or
replacing defective components can reduce direct inflow. Any
modification must still provide appropriate access and ventilation
consistent with safety and regulatory requirements.
7. Which equation is commonly used to estimate flow velocity in
an open-channel portion of a gravity sewer?
A. Boyle's law
B. Darcy's law only
C. Manning's equation
D. Henry's law
Rationale: Manning's equation is widely used to estimate flow
velocity in open-channel flow based on hydraulic radius, slope,
and Manning's roughness coefficient. Collection-system
operators and engineers use it to evaluate hydraulic capacity and
flow conditions in gravity sewers.
8. A sewer has a diameter of 24 inches. What is its nominal
diameter in feet?
