An excavator is positioned to dig a new utility trench directly beneath a 345 kV overhead power line. Which of the following statements applies to the safe operation of the excavator in this scenario?

Question: An excavator is positioned to dig a new utility trench directly beneath a 345 kV overhead power line. Which of the following statements applies to the safe operation of the excavator in this scenario?

Answer options:

• The excavator must maintain a minimum approach distance of 7.6 metres from the power line.
• Only non-metallic tools are permitted for hand digging within the trench.
• A dedicated spotter with communication devices is constantly required for boom proximity. ✅ Excavation is prohibited directly under a power line of this voltage without de-energization.

Correct answer: Excavation is prohibited directly under a power line of this voltage without de-energization.

Explanation: Operating mobile equipment directly beneath power lines of 345 kV or higher requires de-energization or other specialized engineering controls, as per CSA Z248, due to the extreme hazards involved and the large minimum approach distances required (e.g., 9.2m for boom tip or 10.0m for general work depending on jurisdiction). Direct excavation in such proximity is generally prohibited without positive isolation.