STSC Excavation and Trenching Safety

Question 1

Under OSHA 29 CFR 1926 Subpart P, at what depth does an excavation or trench require a protective system (sloping, shoring, or trench box)?

Accepted Answer

5 feet

Answer

3 feet

Answer

4 feet

Answer

6 feet

Question 2

What are the four soil types/classifications used in OSHA's excavation standard, and which requires the most restrictive (flattest) sloping angle?

Accepted Answer

Stable Rock, Type A, Type B, Type C — Type C is most restrictive

Answer

Types A, B, C, D — Type D is most restrictive

Answer

Classes 1, 2, 3, 4 — Class 4 is most restrictive

Answer

Hard, Medium, Soft, Loose — Loose is most restrictive

Question 3

A competent person observing a trench wall notices vertical cracks running parallel to the trench face and a slight outward bulge in the lower portion of the wall. What do these signs indicate?

Accepted Answer

Imminent cave-in risk — immediately remove all workers from the trench

Answer

Normal soil settlement — no action needed

Answer

The soil can be reclassified to Type A due to cohesiveness

Answer

Additional shoring can be added while workers continue

Question 4

Where must excavated material (spoil) be placed relative to the edge of a trench according to OSHA 1926.651(j)(2)?

Accepted Answer

At least 2 feet from the edge of the excavation

Answer

Against the trench wall to provide support

Answer

At least 3 feet from the edge of the excavation

Answer

Within 5 feet of the edge, but secured with barriers

Question 5

What is the maximum distance that a safe means of egress (ladder, steps, or ramp) must be from any worker in a trench deeper than 4 feet?

Accepted Answer

25 feet

Answer

10 feet

Answer

50 feet

Answer

100 feet

Question 6

Before any excavation work begins, what is the REQUIRED first step under OSHA 1926.651(b)?

Accepted Answer

Contact all underground utilities to mark or identify buried facilities

Answer

Complete a written trenching permit

Answer

Obtain approval from the project structural engineer

Answer

Test the soil for Type classification