What maximum vertical side dimension is required for unsupported vertically sided lower portions of excavations 8 feet or less in depth?

The correct answer is the maximum vertical side dimension required for unsupported vertically sided lower portions of excavations 8 feet or less in depth is 3 1/2 feet. This requirement is based on safety standards and regulations that aim to prevent collapses in excavated areas, protecting workers in the vicinity.

Specifically, when an excavation reaches a depth of 4 feet or more, there is a significant risk of collapse, necessitating stringent guidelines for maintaining safe working conditions. The 3 1/2 feet dimension serves as a limit for vertical walls in such excavations to ensure they remain stable without additional support systems. This standard helps minimize the danger of soil movement that could occur if the walls were allowed to be taller, thus enhancing overall site safety.

Understanding these dimensions is crucial for compliance with industry standards, as they are designed to protect workers from the hazards associated with excavation work. The other choices either exceed the recommended height or do not meet the industry standards for safe excavation practices at this depth.