Digging Near Buried Facilities

Tolerance Zone

The flags and paint marks used to mark buried utilities show the approximate location of the actual facility. Utilities have a tolerance zone that runs 24-inches from the utility's outside edges.


Before using mechanized digging equipment in a tolerance zone, you must make sure that someone observes the dig to help the person on the equipment if something doesn't look right. Of course, the best thing to do is find the utility before digging either with hand-dug test holes or vacuum excavation.

Other Safe Digging Tips

  • When exposing a utility while digging, provide adequate support and protection for it. Plus, provide adequate backfill upon completion.
  • If you haven't confirmed the utility response before you dig and encounter an unmarked underground utility, stop and do some investigating. The Positive Response System will tell you if a utility representative wants to be present or has some more information for you before you should be digging. If that's not the case, treat all unmarked lines as live.

Contacting or damaging a buried utility

When you dig around buried utilities, you can contact or damage a buried utility, find an unknown or unmarked facility, or locate a facility in danger of failing. 

If you contact or damage a buried utility, you must:

  • Immediately notify the utility owner of the contact or damage, even if you can't see any damage
  • Stop all excavation in the immediate area that could cause further harm to the utility, until the operator advises you to proceed

If you contact or damage a buried utility, you must not:

  • Ignore it
  • Attempt to repair it
  • Bury, hide or perform any backfilling in the immediate area

If the contact or damage causes an emergency involving danger to life, health, or property, you must immediately:

  • Evacuate your employees and all other endangered persons from the immediate vicinity, to the best of your ability.
  • Call 911 and provide:
    • Exact location of the emergency
    • Nature of the emergency
    • Type of underground utility affected