CO Trenching Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. Which of the following is the primary purpose of shoring in trenching?
A. To increase trench depth
B. To prevent trench collapse
C. To speed up excavation
D. To reduce soil moisture
Rationale: Shoring provides structural support to trench walls to prevent
cave-ins and protect workers.
2. OSHA requires that trenches 5 feet deep or greater must have:
A. A ladder at every 50 feet
B. A protective system such as shoring, shielding, or sloping
C. Water pumps installed
D. Only trained workers inside
Rationale: OSHA mandates protective systems for trenches 5 feet or deeper
to ensure worker safety.
3. What is the maximum safe slope for sandy soil in a trench deeper than
20 feet?
A. 1:1
B. 1.5:1
C. 1.75:1
D. 2:1
,Rationale: Sandy soil has lower cohesion; OSHA provides tables for safe
sloping ratios depending on soil type and trench depth.
4. When is it safe to enter an unshored trench?
A. Anytime with a helmet
B. Never for trenches 5 feet or deeper
C. If it’s raining
D. If the soil is dry
Rationale: Trenches 5 feet or deeper must have protective systems before
entry.
5. What is the primary hazard associated with trenching operations?
A. Noise exposure
B. Dust inhalation
C. Cave-ins
D. Slips on ladders
Rationale: Cave-ins are the leading cause of trenching fatalities, making
prevention the highest priority.
6. Which type of soil is most likely to collapse in a trench?
A. Clay
B. Sandy or granular soil
C. Rocky soil
D. Silty soil
Rationale: Loose granular soils are less cohesive and more prone to
collapse.
7. A trench box is designed to:
A. Remove water from trenches
B. Speed up excavation
C. Protect workers from cave-ins
D. Hold tools
Rationale: Trench boxes shield workers in case of a collapse.
, 8. The minimum distance spoil piles must be placed from a trench edge is:
A. 1 foot
B. 2 feet
C. 2 feet
D. 3 feet
Rationale: OSHA requires spoil piles at least 2 feet from trench edges to
prevent additional collapse risk.
9. What is the first step before beginning trench excavation?
A. Shoring installation
B. Site inspection for underground utilities
C. Operator training
D. Soil testing
Rationale: Locating utilities prevents accidental strikes that can cause injury
or service interruptions.
10. The term “competent person” in trenching refers to:
A. Any worker on site
B. Someone trained to recognize hazards and authorized to take
corrective action
C. Supervisor
D. Inspector from OSHA
Rationale: A competent person must identify hazards and ensure safety
compliance on site.
11. Water accumulation in trenches is hazardous because it:
A. Slows work
B. Increases soil cohesion
C. Reduces soil stability, increasing cave-in risk
D. Makes tools slippery
Rationale: Water saturates soil, making trench walls prone to collapse.
12. What is the maximum depth a worker can safely enter without a
protective system in type B soil?
A. 3 feet
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. Which of the following is the primary purpose of shoring in trenching?
A. To increase trench depth
B. To prevent trench collapse
C. To speed up excavation
D. To reduce soil moisture
Rationale: Shoring provides structural support to trench walls to prevent
cave-ins and protect workers.
2. OSHA requires that trenches 5 feet deep or greater must have:
A. A ladder at every 50 feet
B. A protective system such as shoring, shielding, or sloping
C. Water pumps installed
D. Only trained workers inside
Rationale: OSHA mandates protective systems for trenches 5 feet or deeper
to ensure worker safety.
3. What is the maximum safe slope for sandy soil in a trench deeper than
20 feet?
A. 1:1
B. 1.5:1
C. 1.75:1
D. 2:1
,Rationale: Sandy soil has lower cohesion; OSHA provides tables for safe
sloping ratios depending on soil type and trench depth.
4. When is it safe to enter an unshored trench?
A. Anytime with a helmet
B. Never for trenches 5 feet or deeper
C. If it’s raining
D. If the soil is dry
Rationale: Trenches 5 feet or deeper must have protective systems before
entry.
5. What is the primary hazard associated with trenching operations?
A. Noise exposure
B. Dust inhalation
C. Cave-ins
D. Slips on ladders
Rationale: Cave-ins are the leading cause of trenching fatalities, making
prevention the highest priority.
6. Which type of soil is most likely to collapse in a trench?
A. Clay
B. Sandy or granular soil
C. Rocky soil
D. Silty soil
Rationale: Loose granular soils are less cohesive and more prone to
collapse.
7. A trench box is designed to:
A. Remove water from trenches
B. Speed up excavation
C. Protect workers from cave-ins
D. Hold tools
Rationale: Trench boxes shield workers in case of a collapse.
, 8. The minimum distance spoil piles must be placed from a trench edge is:
A. 1 foot
B. 2 feet
C. 2 feet
D. 3 feet
Rationale: OSHA requires spoil piles at least 2 feet from trench edges to
prevent additional collapse risk.
9. What is the first step before beginning trench excavation?
A. Shoring installation
B. Site inspection for underground utilities
C. Operator training
D. Soil testing
Rationale: Locating utilities prevents accidental strikes that can cause injury
or service interruptions.
10. The term “competent person” in trenching refers to:
A. Any worker on site
B. Someone trained to recognize hazards and authorized to take
corrective action
C. Supervisor
D. Inspector from OSHA
Rationale: A competent person must identify hazards and ensure safety
compliance on site.
11. Water accumulation in trenches is hazardous because it:
A. Slows work
B. Increases soil cohesion
C. Reduces soil stability, increasing cave-in risk
D. Makes tools slippery
Rationale: Water saturates soil, making trench walls prone to collapse.
12. What is the maximum depth a worker can safely enter without a
protective system in type B soil?
A. 3 feet
