All personnel must be at least how many feet away from any moving parts of a trencher?

The distance of 6 feet away from any moving parts of a trencher is established as a safety standard to protect personnel from potential hazards associated with the operation of this machinery. Trencher equipment can have exposed moving parts that pose a risk of entanglement or injury, especially when it's in use. By maintaining a distance of 6 feet, workers reduce the likelihood of accidental contact or injury due to debris or machinery mishaps that can occur during the operation. This safety measure aligns with industry best practices and is designed to ensure the protection of all personnel on the job site.

The other distances suggested do not provide a sufficient margin of safety, as they come closer to the machine's operational area where the risk of injury is significantly higher.