CO Trenching Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the primary purpose of trench shoring?
a) To improve soil compaction
b) To prevent trench collapse
c) To speed up excavation
d) To reduce water accumulation
b) To prevent trench collapse
Rationale: Shoring provides structural support to trench walls to prevent
cave-ins and protect workers.
2. Which type of soil is considered the most unstable for trenching?
a) Clay
b) Sand
c) Silt
d) Rock
b) Sand
Rationale: Sandy soil is granular and does not stick together, making it
prone to collapse.
3. What is the maximum allowable slope for a trench in Type C soil 12
feet deep?
a) 1:1
b) 1:1.5
, c) 1:1.33
d) 1:1.75
a) 1:1
Rationale: Type C soil requires a 1:1 slope (horizontal:vertical) to prevent
collapse.
4. Which OSHA standard governs excavation safety?
a) 1926 Subpart P
b) 1910 Subpart D
c) 1926 Subpart K
d) 1910 Subpart N
a) 1926 Subpart P
Rationale: OSHA 1926 Subpart P outlines requirements for excavation and
trenching safety.
5. How often should a competent person inspect trenches?
a) Daily
b) Before each shift and after a rainstorm
c) Weekly
d) Only before digging
b) Before each shift and after a rainstorm
Rationale: Trenches must be inspected by a competent person to identify
hazards before work begins or after conditions change.
6. Which is a primary hazard of trenching operations?
a) Excessive dust
b) Cave-ins
c) Noise pollution
d) Chemical exposure
b) Cave-ins
Rationale: Cave-ins are the leading cause of fatalities in trenching
accidents.
7. What is the recommended distance for spoil piles from the edge of a
trench?
, a) 1 foot
b) 2 feet
c) 3 feet
d) 4 feet
c) 2 feet
Rationale: Spoil piles should be at least 2 feet from trench edges to reduce
collapse risk.
8. Which type of protective system is used for deep trenches with unstable
soil?
a) Trench boxes
b) Bench excavation
c) Vertical walls
d) None
a) Trench boxes
Rationale: Trench boxes provide protective support to keep walls from
collapsing in deep trenches.
9. When is sloping required in a trench?
a) Only for trenches over 4 feet deep
b) Only for sandy soil
c) Only for trenches near roads
d) Always, regardless of depth
a) Only for trenches over 4 feet deep
Rationale: OSHA requires protective systems, like sloping, for trenches
deeper than 4 feet.
10. What is a competent person in trenching terms?
a) Any worker with 1 year of experience
b) Someone trained to identify hazards and has authority to fix them
c) A project manager
d) A machine operator
Questions And Correct Answers
(Verified Answers) Plus Rationale2026
Q&A| Instant Download Pdf
1. What is the primary purpose of trench shoring?
a) To improve soil compaction
b) To prevent trench collapse
c) To speed up excavation
d) To reduce water accumulation
b) To prevent trench collapse
Rationale: Shoring provides structural support to trench walls to prevent
cave-ins and protect workers.
2. Which type of soil is considered the most unstable for trenching?
a) Clay
b) Sand
c) Silt
d) Rock
b) Sand
Rationale: Sandy soil is granular and does not stick together, making it
prone to collapse.
3. What is the maximum allowable slope for a trench in Type C soil 12
feet deep?
a) 1:1
b) 1:1.5
, c) 1:1.33
d) 1:1.75
a) 1:1
Rationale: Type C soil requires a 1:1 slope (horizontal:vertical) to prevent
collapse.
4. Which OSHA standard governs excavation safety?
a) 1926 Subpart P
b) 1910 Subpart D
c) 1926 Subpart K
d) 1910 Subpart N
a) 1926 Subpart P
Rationale: OSHA 1926 Subpart P outlines requirements for excavation and
trenching safety.
5. How often should a competent person inspect trenches?
a) Daily
b) Before each shift and after a rainstorm
c) Weekly
d) Only before digging
b) Before each shift and after a rainstorm
Rationale: Trenches must be inspected by a competent person to identify
hazards before work begins or after conditions change.
6. Which is a primary hazard of trenching operations?
a) Excessive dust
b) Cave-ins
c) Noise pollution
d) Chemical exposure
b) Cave-ins
Rationale: Cave-ins are the leading cause of fatalities in trenching
accidents.
7. What is the recommended distance for spoil piles from the edge of a
trench?
, a) 1 foot
b) 2 feet
c) 3 feet
d) 4 feet
c) 2 feet
Rationale: Spoil piles should be at least 2 feet from trench edges to reduce
collapse risk.
8. Which type of protective system is used for deep trenches with unstable
soil?
a) Trench boxes
b) Bench excavation
c) Vertical walls
d) None
a) Trench boxes
Rationale: Trench boxes provide protective support to keep walls from
collapsing in deep trenches.
9. When is sloping required in a trench?
a) Only for trenches over 4 feet deep
b) Only for sandy soil
c) Only for trenches near roads
d) Always, regardless of depth
a) Only for trenches over 4 feet deep
Rationale: OSHA requires protective systems, like sloping, for trenches
deeper than 4 feet.
10. What is a competent person in trenching terms?
a) Any worker with 1 year of experience
b) Someone trained to identify hazards and has authority to fix them
c) A project manager
d) A machine operator
