OSHA Excavation & Trenching Quiz — 29 CFR 1926.650-652 Practice Questions — Page 2 of 4
Free OSHA 30-Hour Construction excavation and trenching practice test with 40 realistic scenarios. Soil classification, protective systems, spoil piles, access/egress, competent person duties, hazardous atmospheres with 29 CFR 1926 Subpart P references. (Page 2 of 4)
0 / 10
Q11/ 40
A competent person classifies soil in a 12-foot excavation as Type B. The excavation walls are vertical. What protective system options are available?
✅ Correct Answer: B
1926.652(b)(2) Table B-1: for Type B soil, the maximum allowable slope is 1:1 (45 degrees) for excavations under 20 feet. Vertical walls (90 degrees) are only permitted in stable rock or Type A soil (with specific conditions). Type B soil at 12 feet with vertical walls requires a protective system.
Q12/ 40
A crew is installing a sewer line in a 14-foot deep trench with Type C soil. The contractor plans to use aluminum hydraulic shoring engineered for Type B soil. Can this shoring be used?
✅ Correct Answer: B
1926.652(c)(2): manufacturer's tabulated data shall be followed — the data specifies allowable configurations, depths, and soil types. Type C soil (unconfined compressive strength ≤0.5 tsf, granular soils, or submerged soil) exerts significantly higher lateral pressure. Using shoring rated only for Type B is equivalent to using an undersized protective system.
Q13/ 40
Spoil from a 9-foot deep trench is piled 18 inches from the edge. The pile is 4 feet high. A competent person says nothing. What does 1926.651(j)(1) require?
✅ Correct Answer: B
1926.651(j)(1): material must be kept at least 2 feet from the edge. Additionally, the spoil pile creates a surcharge load on the trench wall — a 4-foot pile of soil (~100 psf per foot of height = 400 psf surcharge) significantly increases lateral pressure on the wall.
Q14/ 40
A worker enters a 5-foot trench for a 'quick repair.' The competent person classified the soil as Type A 3 hours ago. Since then, a water truck passed near the edge multiple times, and tension cracks appear 2 feet from the edge. Is the trench safe without a protective system?
✅ Correct Answer: B
1926.652(a)(1): excavations 5 feet or deeper require protective systems. 1926.651(k)(1): daily inspections required and after any condition change. Vibration and tension cracks indicate the soil has been disturbed — Type A classification is likely no longer valid. A cubic yard of soil weighs over 2,700 lbs and can suffocate a worker in minutes.
Q15/ 40
A 9-foot trench in Type B soil has a trench box 8 feet tall. Workers install pipe 1 foot below the bottom of the box (in a 1-foot 'lip' of exposed soil). Is this acceptable?
✅ Correct Answer: B
1926.652(g)(2): employees must be within the protection of the shield at all times. If the box is 8 feet tall in a 9-foot trench, there is a 1-foot zone at the bottom that is not protected. The box should extend from trench floor to above the trench top, or workers must stay within the protected envelope.
Advertisement
Google AdSense — Responsive In-Article Ad
Q16/ 40
A 7-foot deep foundation excavation in Type A clay has vertical walls. The competent person decides no protective system is needed because Type A is stable. However, the excavation is 20 feet wide. Does width matter?
✅ Correct Answer: B
Narrow trenches benefit from soil arching (horizontal stress transfer between walls), which reduces effective lateral earth pressure. Wide excavations lose this effect — the exposed face behaves more like a retaining wall with full active earth pressure. At 20 feet wide and 7 feet deep, the competent person should be conservative and consider sloping or shoring, especially for longer-duration exposures.
Q17/ 40
Workers are in a 6-foot trench laying conduit. The nearest ladder is 50 feet away. The trench is a straight run. Is this compliant?
✅ Correct Answer: B
1926.651(c)(2): a stairway, ladder, ramp or other safe means of egress shall be located in trench excavations 4 feet or more in depth so as to require no more than 25 feet of lateral travel. With workers 50 feet from the ladder, a second ladder is required at the far end. In a cave-in, seconds matter.
Q18/ 40
A 16-foot excavation in Type C sand has 8 inches of water accumulated from overnight rain. The trench is protected by a trench box. Workers are scheduled to enter. What must the competent person do?
✅ Correct Answer: B
1926.651(h)(1): employees shall not work in excavations with accumulated water unless adequate precautions are taken. Water saturates soil, reducing bearing capacity and potentially causing the trench box to sink. Type C sand with water becomes flowable (quick condition). The competent person must pump out water, verify the floor is stable, and recheck the protective system before workers enter.
Q19/ 40
A backhoe is excavating next to an existing building foundation. The excavation is 10 feet deep, extending 2 feet below the existing footing. What protection is needed?
✅ Correct Answer: B
1926.651(i)(1): where the stability of adjoining buildings is endangered by excavation operations, support systems such as shoring, bracing, or underpinning shall be provided. Excavating below an existing footing removes lateral and bearing support — the foundation can settle, crack, or collapse. An RPE should evaluate and design the support system.
Q20/ 40
A competent person uses the thumb penetration test. The thumb penetrates about 1/2 inch with moderate effort in undisturbed soil. How would this soil be preliminarily classified?
✅ Correct Answer: B
1926 Subpart P Appendix A(d): when the thumb penetrates no more than the length of the thumbnail with moderate effort, it's probably Type B. Type A requires great effort to indent; Type C is easily penetrated. Multiple tests (visual and manual) are required for definitive classification.