CWEA Collection Systems Maintenance Complete Practice Exam Prep Bundle | 150 Questions + Rationales |
Grade 1 & 2
Questions 1–150
1. What is the minimum acceptable oxygen level for entering a confined space without a supplied-air
respirator?
A) 16.5%
B) 19.5%
C) 21.0%
D) 23.5%
Answer B: 19.5%
Rationale: OSHA defines <19.5% as oxygen-deficient; 19.5%–23.5% is safe for entry.
2. Which gas is most commonly associated with "rotten egg" odor in collection systems and is highly
toxic?
A) Methane (CH₄)
B) Carbon dioxide (CO₂)
C) Hydrogen sulfide (H₂S)
D) Sulfur dioxide (SO₂)
Answer C: Hydrogen sulfide (H₂S)
Rationale: H₂S is toxic, corrosive, and has a distinct rotten-egg odor; it is a leading cause of sewer fatalities.
3. A Grade 1 operator finds a manhole cover off. What is the FIRST action?
,A) Replace the cover immediately
B) Set up traffic control and barricade the area
C) Notify the supervisor
D) Check the flow downstream
Answer B: Set up traffic control and barricade the area
Rationale: Public safety is priority; barricade protects pedestrians and vehicles before further action.
4. What is the purpose of a drop manhole?
A) To allow flow to change direction
B) To drop sewer flow from a higher elevation to a lower elevation without creating turbulence
C) To provide access for cleaning
D) To measure flow velocity
Answer B: To drop sewer flow from a higher elevation to a lower elevation without creating
turbulence
Rationale: Drop manholes reduce turbulence and erosion by directing flow vertically using a drop pipe.
5. Which type of pipe is most resistant to hydrogen sulfide corrosion?
A) Cast iron
B) Ductile iron
C) Polyvinyl chloride (PVC)
D) Vitrified clay
Answer C: Polyvinyl chloride (PVC)
Rationale: PVC is non-corrosive and resistant to H₂S attack, unlike metal or concrete pipes.
6. When using a sewer jetter, what is the typical water pressure range for cleaning 8–15 inch lines?
A) 500–800 psi
B) 1,000–2,500 psi
C) 3,000–4,500 psi
D) 5,000–7,000 psi
Answer B: 1,000–2,500 psi
Rationale: Standard jetting pressure for normal mainline cleaning is in the 1,000–2,500 psi range.
,7. A Grade 2 operator must calculate flow in a full pipe. The pipe is 18 inches in diameter and flow
velocity is 3 ft/sec. What is the flow in cubic feet per second (cfs)? (Area of circle = πr²)
A) 2.5 cfs
B) 3.5 cfs
C) 5.3 cfs
D) 6.8 cfs
Answer C: 5.3 cfs
Rationale: Radius = 0.75 ft; Area = π(0.75)² = 1.77 ft²; Q = V×A = 3×1.77 = 5.31 cfs.
8. Before entering a manhole, what is the correct order of gas monitoring?
A) O₂, LEL, H₂S
B) LEL, O₂, H₂S/CO
C) H₂S, O₂, LEL
D) O₂, H₂S, LEL
Answer B: LEL, O₂, H₂S/CO
Rationale: Check combustible gases first, then oxygen, then toxic gases per OSHA guidelines.
9. Which personal protective equipment (PPE) is REQUIRED when working in traffic zones?
A) Hard hat only
B) High-visibility safety vest (ANSI Class 2 or 3)
C) Steel-toe boots only
D) Full-face respirator
Answer B: High-visibility safety vest (ANSI Class 2 or 3)
Rationale: High-visibility vests are mandatory for all roadway workers per MUTCD/CalOSHA.
10. A bucket machine is best used for:
A) Removing roots from small laterals
B) Removing heavy debris, rocks, and hardened deposits
C) Flushing grease from pipe walls
D) Inspecting pipe condition
Answer B: Removing heavy debris, rocks, and hardened deposits
Rationale: Bucket machines (earth augers) pull heavy solids and debris out of the line mechanically.
, 11. What is the typical minimum slope for an 8-inch sanitary sewer?
A) 0.10%
B) 0.40%
C) 1.00%
D) 2.00%
Answer B: 0.40%
Rationale: Minimum slope of 0.40% for 8-inch pipe ensures self-cleansing velocity (≥2 ft/sec).
12. Which type of pump is most commonly used in wastewater lift stations?
A) Positive displacement
B) Diaphragm
C) Centrifugal (non-clog)
D) Rotary gear
Answer C: Centrifugal (non-clog)
Rationale: Non-clog centrifugal pumps handle solids and are standard in wastewater applications.
13. What is "head" in pumping terms?
A) The volume of water in the wet well
B) The height that water must be lifted, expressed in feet
C) The pressure at the pump discharge
D) The horsepower of the motor
Answer B: The height that water must be lifted, expressed in feet
Rationale: Head is the vertical distance the pump must raise the liquid, measured in feet.
14. A Grade 1 operator notices a manhole is leaking inflow during a storm. What is the most likely
cause?
A) Root intrusion
B) A defective frame and cover or cracked manhole barrel
C) High flow velocity
D) Grease blockage downstream
Answer B: A defective frame and cover or cracked manhole barrel
Rationale: Inflow (stormwater) enters through defective covers, frames, or cracks above the water table.
Grade 1 & 2
Questions 1–150
1. What is the minimum acceptable oxygen level for entering a confined space without a supplied-air
respirator?
A) 16.5%
B) 19.5%
C) 21.0%
D) 23.5%
Answer B: 19.5%
Rationale: OSHA defines <19.5% as oxygen-deficient; 19.5%–23.5% is safe for entry.
2. Which gas is most commonly associated with "rotten egg" odor in collection systems and is highly
toxic?
A) Methane (CH₄)
B) Carbon dioxide (CO₂)
C) Hydrogen sulfide (H₂S)
D) Sulfur dioxide (SO₂)
Answer C: Hydrogen sulfide (H₂S)
Rationale: H₂S is toxic, corrosive, and has a distinct rotten-egg odor; it is a leading cause of sewer fatalities.
3. A Grade 1 operator finds a manhole cover off. What is the FIRST action?
,A) Replace the cover immediately
B) Set up traffic control and barricade the area
C) Notify the supervisor
D) Check the flow downstream
Answer B: Set up traffic control and barricade the area
Rationale: Public safety is priority; barricade protects pedestrians and vehicles before further action.
4. What is the purpose of a drop manhole?
A) To allow flow to change direction
B) To drop sewer flow from a higher elevation to a lower elevation without creating turbulence
C) To provide access for cleaning
D) To measure flow velocity
Answer B: To drop sewer flow from a higher elevation to a lower elevation without creating
turbulence
Rationale: Drop manholes reduce turbulence and erosion by directing flow vertically using a drop pipe.
5. Which type of pipe is most resistant to hydrogen sulfide corrosion?
A) Cast iron
B) Ductile iron
C) Polyvinyl chloride (PVC)
D) Vitrified clay
Answer C: Polyvinyl chloride (PVC)
Rationale: PVC is non-corrosive and resistant to H₂S attack, unlike metal or concrete pipes.
6. When using a sewer jetter, what is the typical water pressure range for cleaning 8–15 inch lines?
A) 500–800 psi
B) 1,000–2,500 psi
C) 3,000–4,500 psi
D) 5,000–7,000 psi
Answer B: 1,000–2,500 psi
Rationale: Standard jetting pressure for normal mainline cleaning is in the 1,000–2,500 psi range.
,7. A Grade 2 operator must calculate flow in a full pipe. The pipe is 18 inches in diameter and flow
velocity is 3 ft/sec. What is the flow in cubic feet per second (cfs)? (Area of circle = πr²)
A) 2.5 cfs
B) 3.5 cfs
C) 5.3 cfs
D) 6.8 cfs
Answer C: 5.3 cfs
Rationale: Radius = 0.75 ft; Area = π(0.75)² = 1.77 ft²; Q = V×A = 3×1.77 = 5.31 cfs.
8. Before entering a manhole, what is the correct order of gas monitoring?
A) O₂, LEL, H₂S
B) LEL, O₂, H₂S/CO
C) H₂S, O₂, LEL
D) O₂, H₂S, LEL
Answer B: LEL, O₂, H₂S/CO
Rationale: Check combustible gases first, then oxygen, then toxic gases per OSHA guidelines.
9. Which personal protective equipment (PPE) is REQUIRED when working in traffic zones?
A) Hard hat only
B) High-visibility safety vest (ANSI Class 2 or 3)
C) Steel-toe boots only
D) Full-face respirator
Answer B: High-visibility safety vest (ANSI Class 2 or 3)
Rationale: High-visibility vests are mandatory for all roadway workers per MUTCD/CalOSHA.
10. A bucket machine is best used for:
A) Removing roots from small laterals
B) Removing heavy debris, rocks, and hardened deposits
C) Flushing grease from pipe walls
D) Inspecting pipe condition
Answer B: Removing heavy debris, rocks, and hardened deposits
Rationale: Bucket machines (earth augers) pull heavy solids and debris out of the line mechanically.
, 11. What is the typical minimum slope for an 8-inch sanitary sewer?
A) 0.10%
B) 0.40%
C) 1.00%
D) 2.00%
Answer B: 0.40%
Rationale: Minimum slope of 0.40% for 8-inch pipe ensures self-cleansing velocity (≥2 ft/sec).
12. Which type of pump is most commonly used in wastewater lift stations?
A) Positive displacement
B) Diaphragm
C) Centrifugal (non-clog)
D) Rotary gear
Answer C: Centrifugal (non-clog)
Rationale: Non-clog centrifugal pumps handle solids and are standard in wastewater applications.
13. What is "head" in pumping terms?
A) The volume of water in the wet well
B) The height that water must be lifted, expressed in feet
C) The pressure at the pump discharge
D) The horsepower of the motor
Answer B: The height that water must be lifted, expressed in feet
Rationale: Head is the vertical distance the pump must raise the liquid, measured in feet.
14. A Grade 1 operator notices a manhole is leaking inflow during a storm. What is the most likely
cause?
A) Root intrusion
B) A defective frame and cover or cracked manhole barrel
C) High flow velocity
D) Grease blockage downstream
Answer B: A defective frame and cover or cracked manhole barrel
Rationale: Inflow (stormwater) enters through defective covers, frames, or cracks above the water table.
