A plumbing crew is excavating a trench for a new sanitary lateral. The trench is 1.8 metres deep, 0.9 metres wide, and the soil is a cohesive type (e.g., clay). What is the minimum slope angle required for the trench walls if shoring is not used, according to general safety standards?

Question: A plumbing crew is excavating a trench for a new sanitary lateral. The trench is 1.8 metres deep, 0.9 metres wide, and the soil is a cohesive type (e.g., clay). What is the minimum slope angle required for the trench walls if shoring is not used, according to general safety standards?

Answer options: ✅ 45 degrees

• 60 degrees
• Horizontal to vertical ratio of 1:1
• Vertical walls are acceptable for cohesive soil

Correct answer: 45 degrees

Explanation: For a trench in cohesive soil, general safety standards often require a maximum slope of 45 degrees (or a 1:1 horizontal to vertical ratio) when shoring is not used and the trench is deeper than 1.2 metres. Steeper slopes or vertical walls without shoring are unsafe and can lead to collapses, even in cohesive soil.