Excavation and Trenching Safety Flashcards
6 cards from real STSC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Excavation and Trenching Safety flashcards as text
What is a 'competent person' required to do regarding excavation inspections under OSHA Subpart P?
Answer: Inspect before the start of work, as needed during the shift, and after rain or other events that could increase hazard
OSHA 1926.651(k)(1) requires the competent person to inspect excavations, adjacent areas, and protective systems daily before work and as needed throughout the shift — especially after rain, freezing, or other hazard-increasing events.
When is atmospheric testing required before workers enter an excavation?
Answer: When the excavation may reasonably be expected to have an atmosphere containing harmful levels of gases, vapors, or oxygen deficiency
OSHA 1926.651(g)(1) requires atmospheric testing before workers enter any excavation that could reasonably be expected to have a hazardous atmosphere — including areas near landfills, fuel lines, sewer systems, or excavations where biological decomposition could occur.
A trench is being excavated in Type B soil. The trench is 10 feet deep. What is the required horizontal setback (slope) for each side of the trench?
Answer: 5 feet from the base on each side (1:1 ratio)
Type B soil requires a slope of 1:1 (horizontal to vertical). For a 10-foot deep trench, each side must be set back 10 feet horizontally from the base — 5 feet measured from the trench centerline if full-width sloping is used.
What is the OSHA definition of a 'trench' as distinct from a general 'excavation'?
Answer: An excavation that is narrower than it is deep, with a maximum width of 15 feet at the bottom
OSHA 1926.650 defines a trench as a narrow excavation in which the depth is greater than the width, with a maximum width of 15 feet measured at the bottom.
A trench protection system uses a hydraulic trench shield (trench box). Where must workers be positioned relative to the shield when working in the trench?
Answer: Workers must remain inside the protective shield at all times during excavation operations
The entire purpose of a trench shield is to protect workers from cave-ins. Workers must remain inside the shield at all times during excavation — working outside the shield's protection defeats its purpose.
After a significant rainfall, the competent person inspects a trench in Type A soil and finds that water has accumulated in the bottom of the trench and the walls show some cracking. What must happen?
Answer: The trench must be reclassified as at most Type C, water must be controlled, and the trench re-evaluated before workers re-enter
Water intrusion and cracking downgrade soil classification. Soil that was Type A can become Type C when subjected to water saturation. The trench must be reclassified, water controlled, and the protective system re-evaluated before worker re-entry.