CWEA COLLECTIONS SYSTEM MAINTENANCE GRADE 3 EXAM PREP – 200+ Q&AS WITH RATIONALES (CERTIFICATION PRACTICE TEST)

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COLLECTIONS SYSTEM MAINTENANCE

GRADE 3-STUDY GUIDE 2026|REAL EXAM

QUESTIONS AND ANSWERS|A+GRADE

ASSURED

1. Why are gasoline and volatile solvents objectionable when

present in a sewer?

 A) They increase the biological oxygen demand

 B) They produce an explosion hazard

 C) They corrode concrete pipes

 D) They generate hydrogen sulfide

 Answer: B

 Rationale: Gasoline and volatile solvents produce

flammable vapors that can accumulate in sewer

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headspaces, creating a serious risk of fire or explosion

when combined with an ignition source. The vapors are

lighter than air and tend to collect in high points and

manholes.

2. You should never attempt to install, maintain, repair or replace

electrical equipment panels, controls, wiring or circuits unless:

 A) You have been told to do so by a supervisor

 B) You know what you are doing, are qualified and are

authorized

 C) The power has been turned off at the main breaker

 D) A second person is present as a safety observer

 Answer: B

 Rationale: Working on electrical equipment requires

specific training, qualification, and employer authorization.

Without these, the worker places themselves and others at

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risk of electrocution, arc flash, or equipment damage, and

may violate OSHA regulations.

3. When working in confined spaces or sewers, what form of

lighting would you use?

 A) Mirrors to direct sunlight or explosion-proof lighting

 B) Ordinary electric lights with standard bulbs

 C) Propane, gas or kerosene lanterns

 D) Battery-operated headlamps only

 Answer: A

 Rationale: In confined spaces where explosive gases may

be present, only intrinsically safe or explosion-proof lighting

must be used to prevent ignition. Mirrors directing sunlight

are a historical alternative when electrical lighting cannot

be safely deployed.

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4. What can happen if water-based substances are used to

extinguish electrical fires?

 A) Nothing – water is effective on all fires

 B) The fumes are not harmful

 C) Receive an electrical shock

 D) They will corrode the electrical contacts

 Answer: C

 Rationale: Water conducts electricity. Applying water to an

electrical fire creates a path for current to flow through the

water stream back to the operator, causing severe electrical

shock or electrocution.

5. When testing a manhole for explosive gases, when should the

first tests be made?

 A) After removing the manhole cover

 B) Before removing the manhole cover