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

OSHA 1926.652(a)(1) requires a protective system for all excavations 5 feet or deeper in depth, except those made entirely in stable rock.

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

OSHA uses Stable Rock, Type A (most stable), Type B, and Type C (least stable). Type C soil requires the flattest slope — 1.5:1 (horizontal:vertical) — reflecting its instability.

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

Vertical cracks parallel to the trench face and outward wall bulging are critical warning signs of imminent cave-in. Workers must be immediately removed and no re-entry permitted until the competent person determines it is safe.

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

OSHA 1926.651(j)(2) requires that excavated material (spoil) be placed at least 2 feet (0.61 m) from the edge of the excavation to prevent it from falling back into the trench and to reduce surcharge loading on trench walls.

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

OSHA 1926.651(c)(2) requires that ladders, steps, ramps, or other safe means of egress be located within 25 lateral feet of all workers in trenches 4 feet or deeper.

(STSC) Safety Trained Supervisor Construction Practice Test

(STSC) Safety Trained Supervisor Construction Practice Test

STSC Excavation and Trenching Safety