What is a “cross bore?”

A cross bore occurs when a new natural gas line is installed using a trenchless method and intersects an existing underground utility.


Trenchless installation methods, commonly referred to as trenchless technology, could include use of the following: directional drills, auger boring equipment and plowing.

Take safety precautions

More and more utilities install underground lines using trenchless technology. Excavators are required to call 811 and request the marking of utility lines in the area. Often, sewer lines are not marked, leaving the potential for natural gas lines to be bored through the sewer lines. A cross bore can go undetected for months, even years. Eventually, a backup develops, and a plumber is called to remove the blockage. This almost always damages the utility line bored through the sewer line. If a natural gas line is damaged, gas can migrate into homes and buildings and endanger your safety and your property.

Before starting the process of cleaning out a sewer pipeline, remember to first use a camera to identify the condition of the sewer pipeline.

cross bores diagram

Awareness of work conditions

During the process of cleaning out a sewer pipeline, be alert to any unusual conditions, which may include:
  • Hissing sounds 
  • Natural gas odor 
  • Blowing dirt 
  • Bubbling water 
If you suspect a natural gas leak or that contact with a natural gas line has occurred:
  • Stop all work 
  • Leave the premises immediately and instruct others to leave the premises immediately 
  • Contact Piedmont Natural Gas from a safe location at 800.752.7504 
  • Call 911 
  • Keep others a safe distance away 
  • Do not operate any equipment 
  • Eliminate any source of ignition 
  • Do not operate any pipeline equipment or facility