No person should be permitted to work in a trench or pit in sandy clay soil that has unsupported sides higher than what height?

The specified height of unsupported sides at 5 feet is established to ensure safety when working in trenches or pits, particularly in sandy clay soil, which can be prone to collapse under certain conditions. Trenches or pits that exceed this height involve a significant risk of cave-ins, which can have serious, potentially fatal consequences for workers. This standard is based on soil mechanics and an understanding of how different soil types behave under load.

Among the options provided, regulating work at this 5-foot depth is consistent with guidelines found in occupational safety standards, which often detail that trenches deeper than this typically require shoring or other protective measures. By adhering to this height restriction, the likelihood of accidents due to soil failure is substantially reduced, thereby promoting a safer working environment.

Choosing a height lower than 5 feet could fail to address the risks posed by the specific soil type in question, while a height exceeding this could significantly increase danger, which is why the 5-foot figure is important.