During a trench excavation for a water main, you encounter a section of unstable, sandy soil approximately 3 metres deep. The project specifications require the trench bottom to be 1.2 metres wide to accommodate the pipe and bedding. What is the most appropriate action to ensure trench stability and worker safety in this situation?

Question: During a trench excavation for a water main, you encounter a section of unstable, sandy soil approximately 3 metres deep. The project specifications require the trench bottom to be 1.2 metres wide to accommodate the pipe and bedding. What is the most appropriate action to ensure trench stability and worker safety in this situation?

Answer options:

• Continue excavating as planned, as the pipe will provide support once installed.
• Switch to a V-shaped trench profile with a 1:1 slope without shoring. ✅ Implement a proper shoring system or employ a trench box before workers enter.
• Reduce the trench depth to 1.5 metres and install the pipe in two sections.

Correct answer: Implement a proper shoring system or employ a trench box before workers enter.

Explanation: Unstable, sandy soil at a depth of 3 metres presents a high risk of trench collapse. The most appropriate and legally compliant action is to implement a robust shoring system or use a trench box to protect workers. V-shaped trenches with 1:1 slopes are generally not sufficient for unstable soils at this depth without additional support, and continuing without mitigation or reducing depth unilaterally are unsafe and impractical solutions.