A utility cross bore is an unintended intersection of an existing underground utility such as a natural gas pipeline or sewer line by a second utility. This happens when utilities are installed using trenchless drilling, also known as boring. The Union Gas Cross Bore Safety Program deals specifically with the unintended intersection of a sewer line by a natural gas line.
Instances of natural gas lines intersecting sewer lines are rare but they have been found in the Union Gas service area. Left undisturbed they do not pose an immediate safety risk, although they may cause a sewer blockage. However if the gas line is damaged through sewer cleaning activity, the natural gas may enter the sewer line and pose an immediate safety risk. Although there have been no serious incidents in Canada there have been over 20 in the United States.
Like many natural gas distribution utilities, Union Gas often uses trenchless technologies to install underground pipelines. Trenchless installation is very effective in established areas as it all but eliminates the disturbance to roads, environmentally sensitive areas, driveways, gardens and lawns, as well as the roots of large trees, that occurs when digging an open trench.
But because the trenchless drilling machine operator can't actually see the head of the boring equipment during tunnelling, they rely heavily on accurate "locates" to show them the location of other existing underground utilities. Unlike other types of underground utilities, sewers are traditionally difficult to locate. They are made of non-metallic materials and are installed without any other type of aid to allow them to be located from above ground. Sewers can also be very old, records can be incomplete and "ownership" of the sewer infrastructure usually changes from the municipality to the property owner at some point between the sewer main and the building. In addition, if for some reason either the gas line or the sewer line was installed at an unusual depth and the sewer line could not be accurately located, a conflict can occur.
The most important thing you can do is call Ontario One Call at 1-800-400-2255 and request a free sewer safety inspection before using mechanical or high-pressure water jetting equipment to try to clear a blockage beyond the walls of the building. A blocked sewer can be a stressful situation and you'll want it resolved fast. That's why these inspections are treated as emergency calls with a goal of resolving the issue as quickly as possible. Your safety is the number one goal.
Switching to natural gas? Union Gas or one of our construction partners will visit you to determine where existing utilities are already installed on your property. Please make sure they are provided with prompt and accurate information.
You may also be contacted by Union Gas or one of our construction partners when a new construction or a gas line replacement project is being planned for your neighbourhood. Again, please provide them with the most accurate information possible so a cross bore on your property can be avoided.