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

Which atmospheric condition in an excavation requires air monitoring BEFORE workers enter?

Answer: Excavation is more than 4 feet deep AND oxygen-deficient or hazardous atmospheres may be present

OSHA 29 CFR 1926.651(g) requires testing for hazardous atmospheres in excavations deeper than 4 feet where such conditions may reasonably be expected.

A utility strike occurs during excavation. Which action should be taken FIRST?

Answer: Stop work, remove workers, and notify the utility owner

Worker safety is paramount — immediately stop work, evacuate all personnel, and then notify the utility company to assess and control the hazard.

Under OSHA standards, how often must a competent person inspect an excavation?

Answer: Before each work shift and after any event that could affect its integrity

OSHA 29 CFR 1926.651(k) requires inspection by a competent person before each shift and after any rain, freeze/thaw, or other potentially hazardous event.

What is the required minimum oxygen concentration level for workers to safely enter a trench or excavation?

Answer: 19.5%

OSHA defines an oxygen-deficient atmosphere as below 19.5% oxygen by volume; workers may not enter without respiratory protection below this level.

When is a registered professional engineer (PE) required to design a protective system for an excavation?

Answer: Tabulated data or manufacturer data is not available for the site conditions

A PE-designed system is required when site conditions fall outside the scope of OSHA Appendix tables or manufacturer-supplied tabulated data under 29 CFR 1926.652(b)(4).

What is the OSHA requirement for means of egress from a trench that is 4 feet or more in depth?

Answer: A ladder, stairway, or ramp must be present within 25 feet of lateral travel

OSHA 29 CFR 1926.651(c)(2) requires a means of egress (ladder, ramp, or stairway) within 25 lateral feet of any worker in a trench 4 or more feet deep.

Which soil test uses a penetrometer pushed into freshly cut soil to estimate unconfined compressive strength?

Answer: Manual penetrometer test

A pocket penetrometer measures the resistance of soil in tons per square foot (tsf) to help classify soil type for excavation safety decisions.