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CHST - Construction Health and Safety Technician Excavation and Trenching Safety Questions and Answers Flashcards

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  1. Under OSHA 29 CFR 1926.652, what is the maximum allowable slope for Type C soil when using the sloping method of protection?

    Answer: 1.5H:1V (34°)

    Type C soil, the least stable classification, requires a slope of 1.5H:1V (approximately 34 degrees from horizontal).

  2. A competent person inspects an excavation after a rainstorm. What is the MOST important action if the walls show signs of tension cracking?

    Answer: Remove all workers and reassess protective systems

    Tension cracks are a warning sign of imminent collapse; all workers must be removed until a competent person determines the excavation is safe.

  3. What is the minimum distance that excavated spoil (dirt) must be kept from the edge of a trench?

    Answer: 2 feet

    OSHA 29 CFR 1926.651(j)(2) requires excavated material to be kept at least 2 feet from the edge of a trench to prevent cave-in surcharge loading.

  4. Which condition would cause a competent person to reclassify soil from Type B to Type C?

    Answer: Water seeping into the excavation from the sides

    Fissured soil or soil from which water is seeping must be classified as Type C under OSHA Appendix B to Subpart P.

  5. When using a hydraulic shoring system, what step must occur BEFORE workers enter the trench?

    Answer: Install and extend all hydraulic cylinders to rated capacity

    Hydraulic cylinders must be installed and pressurized to their rated capacity before workers enter to ensure the system provides adequate lateral support.

  6. A trench is 7 feet deep in Type A soil with no other hazards. Which protective system option is acceptable under OSHA Appendix B?

    Answer: Sloping at 0.75H:1V

    Type A soil allows a maximum allowable slope of 0.75H:1V (approximately 53 degrees), making it the least flat slope permissible by OSHA.

  7. What is the primary purpose of a trench box (shield) as a protective system?

    Answer: To protect workers from cave-ins by shielding them, not preventing soil movement

    A trench shield (box) protects workers inside it from a cave-in but does not prevent soil movement — it provides a protected zone for workers to occupy.