A new excavator operator is tasked with digging a trench 2.5 metres deep in unstable soil conditions on a construction site in Alberta. The trench will be occupied by workers for pipe installation. What is the minimum protective system requirement for this trench according to Alberta's Occupational Health and Safety Code?

Question: A new excavator operator is tasked with digging a trench 2.5 metres deep in unstable soil conditions on a construction site in Alberta. The trench will be occupied by workers for pipe installation. What is the minimum protective system requirement for this trench according to Alberta's Occupational Health and Safety Code?

Answer options:

• Sloping the trench walls to an angle no steeper than 1:1 (45 degrees) from the trench bottom. ✅ Using a trench box or other engineered protective system designed for the soil conditions.
• Ensuring workers wear fall protection while working inside the trench.
• Continuously monitoring the trench for signs of collapse and evacuating when observed.

Correct answer: Using a trench box or other engineered protective system designed for the soil conditions.

Explanation: For trenches 1.2 metres deep or more where workers are present, a protective system like shoring or a trench box is mandatory in unstable soil conditions. Simple sloping to 1:1 is often insufficient for safety and may not meet code requirements in unstable soil. Fall protection is not an alternative to shoring, and continuous monitoring doesn't prevent a collapse.