For what condition must conductors' locations be identified with a warning ribbon?

Conductors' locations must be identified with a warning ribbon when they are buried 30 inches or more below grade to ensure safety and prevent accidental damage during excavation or construction activities. This requirement is set to alert individuals who may be digging in the vicinity that there are underground electrical conductors present. The use of a warning ribbon at this depth helps to avoid potential hazards associated with striking electrical lines, which can lead to severe injury or even fatalities, as well as power outages and damage to infrastructure.

The established depth provides adequate protection for the conductors while also ensuring that they are easily identifiable to those working above them. The visibility of the ribbon serves as a reminder for safety, encouraging workers to exercise caution and take the appropriate measures to avoid disturbing the buried conductors.