A wheel loader operator has just completed an excavation near a marked 600V underground electrical cable. The 'as-built' drawings indicate the cable is buried at a nominal depth of 0.9 metres. Due to ground disturbance, the exact depth may vary by ±0.15 metres. If the excavator's bucket articulation height is 0.8 metres, what is the maximum depth the wheel loader can safely excavate without requiring further specific precautions for the utility, assuming no ground frost?

Question: A wheel loader operator has just completed an excavation near a marked 600V underground electrical cable. The 'as-built' drawings indicate the cable is buried at a nominal depth of 0.9 metres. Due to ground disturbance, the exact depth may vary by ±0.15 metres. If the excavator's bucket articulation height is 0.8 metres, what is the maximum depth the wheel loader can safely excavate without requiring further specific precautions for the utility, assuming no ground frost?

Answer options: ✅ 0.60 metres

• 0.75 metres
• 0.90 metres
• 1.05 metres

Correct answer: 0.60 metres

Explanation: The cable could potentially be as shallow as 0.9 m - 0.15 m = 0.75 m. CSA Z247-19 'Work in Confined Spaces' and provincial OHS regulations (e.g., BC WSBC OHS Reg. 20.10) typically require hand-digging or alternative safe methods within 1.0 m of underground utilities once located, especially if the exact depth is uncertain. To maintain a hand-digging clearance of at least 15 cm above the potential shallowest point of the cable, 0.75 m (shallowest depth) - 0.15 m (hand-dig clearance) = 0.60 metres. Therefore, any mechanical excavation deeper than 0.60m must trigger additional precautions like hand-digging.