How high must shielding or a trench box extend above an excavation?

The correct choice states that shielding or a trench box must extend at least 18 inches above the excavation. This requirement is crucial for ensuring the safety of workers within the excavation site. The height of 18 inches is designed to accommodate factors such as the potential for soil movement and provide a safety buffer in case of unexpected collapses. Shielding equipment is intended to protect workers from cave-ins and falls, which are significant hazards in excavation work.

By having the shielding extend a minimum of 18 inches, it helps ensure that there is sufficient coverage while workers are operating in or near the trench. This measure contributes to reducing the risk of injury or fatality resulting from trench collapses, which can occur suddenly and with great force. Therefore, adhering to the specified height is a critical aspect of excavation safety protocols, as mandated by safety regulations and best practices in the industry.