According to OSHA, excavations that reach a depth of what measurement require an adequate protective system?

The correct answer is based on OSHA regulations, which dictate that any excavation reaching a depth of 5 feet or more must be protected by an adequate protective system. This regulation is in place to ensure worker safety, as excavations can be susceptible to cave-ins, which pose significant risks. When the depth of an excavation reaches 5 feet, there is a substantial possibility of encountering hazardous conditions that could jeopardize the safety of workers. Therefore, proper protective measures such as trench boxes, shoring, or sloping must be implemented at this depth to mitigate risks effectively.

Understanding this requirement emphasizes the importance of adhering to safety standards in excavation work, as worker safety is paramount in construction and related fields.