OSHA Excavation & Trenching Quiz — 29 CFR 1926.650-652 Practice Questions — Page 3 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 3 of 4)
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Q21/ 40
A supervisor wants workers to enter a 15-foot deep manhole excavation with aluminum hydraulic shoring. The manufacturer's tabulated data for Type B soil shows a maximum depth of 12 feet for this configuration. The supervisor says 'it's only 3 feet deeper.' Is this acceptable?
✅ Correct Answer: B
1926.652(c)(2): manufacturer's tabulated data shall be followed. At 15 feet vs. 12 feet max, lateral earth pressure is approximately 25% higher. The shoring cylinders and rails are loaded beyond design capacity. The correct action: slope the top 3 feet at 1:1, use a different configuration rated for 15 feet in Type B, or have an RPE design the system.
Q22/ 40
A trench box is lowered into a 13-foot deep excavation. The box is 6 feet wide and suspended 2 feet above the trench floor by the excavator while workers work at floor level. Is this acceptable?
✅ Correct Answer: B
1926.652(g)(1)(ii): shields shall be securely installed to prevent lateral movement. A suspended shield is not securely installed. If the excavator's hydraulics bleed, the box can descend, crushing workers. The box must be set on the trench floor so its weight is supported by the ground.
Q23/ 40
Traffic vibrations from heavy trucks are noticeable at a trench edge. The competent person classified the soil as Type B this morning. Small clods of soil are falling from the trench wall. What should be done?
✅ Correct Answer: B
1926.651(k)(1): the competent person shall inspect after any occurrence that could affect stability. Traffic vibration can increase pore water pressure, rearrange soil particles, and propagate tension cracks. Falling clods are a warning sign of wall degradation. The soil may need to be reclassified to Type C.
Q24/ 40
A trench is dug through an area with fill material (construction debris, gravel, soil mix). The competent person cannot classify it using standard methods. The trench is 8 feet deep with vertical walls. How should this be classified?
✅ Correct Answer: B
1926 Subpart P Appendix A(b): 'Type C' includes gravel, submerged soil, AND 'any soil that has been previously disturbed.' Fill material is previously disturbed by definition. Appendix A(c)(1): Type A soil must NOT have been previously disturbed. Heterogeneous fill with debris is unpredictable and must be classified as Type C, requiring a protective system rated for Type C at 8 feet.
Q25/ 40
Workers in a 7-foot trench have a ladder that extends 2 feet above grade (the ladder is 9 feet long). Subpart X requires ladders to extend at least 3 feet above the landing surface. Does this apply?
✅ Correct Answer: B
1926.651(c)(2): egress from trench excavations shall comply with 1926 Subpart X. 1926.1053(b)(1): portable ladders shall extend at least 3 feet above the upper landing surface. Without adequate extension, a worker lacks a secure grip while stepping off and can fall backward into the trench. The ladder must also be secured to prevent displacement.
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Q26/ 40
A contractor is excavating a basement 18 feet deep in Type B soil. The sides are sloped at 1:1 per Table B-1. Halfway down, there is a 6-foot wide bench before the slope continues. Workers stand on the bench. Is this adequate?
✅ Correct Answer: B
1926.652(b)(2) Table B-1 allows benching for Type B soil. However, Appendix B specifies specific configurations — standard bench dimensions are based on vertical spacing (typically 5-foot max between benches) and horizontal width (typically 4-foot minimum). An arbitrary bench at a random height may not meet the prescribed configuration. The contractor should follow the benching diagram or have an RPE design the system.
Q27/ 40
During pipe-laying, the trench box is dragged forward by the excavator as pipe is laid. Workers remain inside the box during movement. The competent person says 'everyone does this.' What does OSHA require?
✅ Correct Answer: B
1926.652(e)(1): employees shall not be permitted in excavations when protective systems are being installed, removed, or modified, unless the system was designed by an RPE to allow employees to remain. Moving a shield is a modification — the soil behind becomes temporarily unsupported. Workers must exit, the shield moved, and re-enter only after the competent person verifies proper positioning.
Q28/ 40
A 22-foot deep excavation is being designed. Soil is Type B. Table B-1 applies to excavations up to 20 feet. What is required?
✅ Correct Answer: B
1926.652(b)(3): excavations over 20 feet in depth require a protective system designed by an RPE. Table B-1 sloping/benching configurations are valid only for excavations 20 feet deep or less. This is a hard threshold — no amount of contractor experience can substitute for the RPE requirement at depths exceeding 20 feet.
Q29/ 40
Water seeps into a 6-foot trench through the wall. A sump pump removes it, discharging 10 feet from the edge. A worker is concerned about erosion. Is this valid?
✅ Correct Answer: B
1926.651(h)(1): where water accumulates, precautions shall be taken. Water seeping through a trench wall carries soil particles (piping), creating voids behind the face. Saturated soil is, by definition, not Type A or B. Well-point dewatering (lowering the water table before excavation) is preferable to sump pumping alone.
Q30/ 40
A worker in a 9-foot trench with a trench box removes their hard hat because 'the box protects us.' A tool falls from the surface into the trench. What hazard does the trench box NOT protect against?
✅ Correct Answer: B
1926.651(j)(1): protection from falling materials is a separate requirement from cave-in protection. The trench box has no roof — objects falling from the surface enter vertically. 1926.100(a): protective helmets are required where there is danger of head injury from falling objects. A tool dropped from 9 feet imparts significant impact force.