CA D56 Trenching Contractor Exam

CA D56 Trenching Contractor Exam Questions And Correct Answers (Verified Answers) Plus Rationale2026 Q&A| Instant Download Pdf

• What is the minimum slope ratio for trenches less than 20 feet deep in

stable rock?

A. 1:1

B. 3/4:1

C. 1/2:1

D. 2:1

Rationale: OSHA regulations specify a minimum slope of 1/2:1 for stable rock to prevent cave-ins.

2. Before entering a trench, a contractor must:

• Wear ear protection only
• Inspect the trench for hazards
• Fill the trench halfway with water
• Begin digging

Rationale: Trench inspections are required before entry to identify

hazards such as cave-ins, water accumulation, or gas pockets.

• Which protective system is commonly used for trenches deeper than 5

feet in loose soil?

• None
• Sloping
• Shoring
• Shielding

Rationale: Shoring supports trench walls and prevents collapse in

loose or unstable soil. 1 / 3

• The term "competent person" in trench safety refers to someone who:
• Is licensed only
• Can identify hazards and has authority to fix them
• Works for the contractor
• Has taken a first aid course

Rationale: A competent person must recognize hazards and have the

authority to take corrective actions.

• Which soil type is considered Type C under OSHA classification?
• Rock
• Sandy soil
• Clay
• Stable silt

Rationale: Type C is the least stable soil, including sand and loamy

soils, requiring maximum protective measures.

• How often should trenches be inspected after a rainstorm?
• Once a week
• Once a month
• Before each shift and as needed
• Only before the start of the project

Rationale: Inspections must occur frequently, especially after events

like rain that can increase collapse risk.

• The maximum allowable slope for a trench in Type B soil that is 10

feet deep is:

A. 1/4:1

B. 1/2:1

C. 1:1

D. 2:1

Rationale: OSHA requires Type B soil to have a slope of 1:1 for trenches up to 20 feet deep.

• Which of the following is NOT a hazard associated with trench work?
• Cave-ins
• Falling loads
• Hazardous atmospheres
• Excessive sunlight

Rationale: While sunlight is a general safety concern, it is not a

primary trench hazard. 2 / 3

9. Trench boxes are used to:

• Measure trench depth
• Protect workers from cave-ins
• Store tools
• Guide excavation equipment

Rationale: Trench boxes provide a protective shield around workers.

• Competent persons must have which type of training?
• Only first aid
• OSHA excavation standards training
• Ability to detect hazards and knowledge of soil types
• Equipment operator license

Rationale: Competent persons must recognize hazards and

implement protective measures.

• Which of the following is a safe practice for trench egress?
• Using ladders every 25 feet
• Providing ladders or ramps within 25 feet of workers
• Jumping out quickly
• Climbing trench walls directly

Rationale: OSHA requires safe access within 25 feet of workers in

trenches 4 feet deep or more.

• Which of these materials should be kept at least 2 feet from the

edge of a trench?

• Loose soil
• Equipment
• Spoils
• All of the above

Rationale: Materials and equipment too close to trench edges

increase collapse risk.

• What is the primary purpose of a benching system?
• To reduce trench wall collapse
• To store equipment
• To mark trench depth
• To measure soil type

Rationale: Benching creates steps in trench walls to reduce pressure

and collapse risk.

14. Oxygen-deficient atmospheres in trenches are dangerous because:

• Workers may slip
• / 3