How should the sides of a trench over 4 feet deep be excavated to ensure safety?

The most effective method for excavating the sides of a trench over 4 feet deep to ensure safety involves shelved, sloped, or sheeted techniques. This approach is critical in preventing cave-ins, which pose significant hazards in trench work. Proper sloping refers to angling the sides of the trench to reduce the risk of the walls collapsing, making it safer for workers who need to enter the trench. Sheeting refers to using materials to support the trench walls, preventing soil from collapsing inward. In some cases, shelving can be employed to create platforms that further enhance stability.

Choosing to excavate the sides vertically, as indicated in the incorrect answer, does not provide adequate support and greatly increases the risk of a cave-in. Additionally, allowing excavation without any form of protection is unsafe and violates standard safety regulations. Simply using a ladder does not address the potential hazards associated with the trench walls themselves, as it only provides a means for entry and exit without improving wall stability. Ensuring that proper methods such as shelving, sloping, or sheeting are used is essential for maintaining a secure working environment in deep trenches.