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These materials will help you learn more about safe digging.

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There are dangers under the ground

There are numerous underground hazards that could cause serious injuries. Hitting gas, electric, or other high-pressure pipes and lines could have fatal consequences.
We must all prevent damages to protect our communities.

Never assume it is safe to dig

  • Nicking a gas line could lead to leaks, fire, or explosions.
  • Damaging electrical cables could shock or electrocute you.
  • Hitting water or sewer lines could cause flying debris, floods, contamination, and environmental hazards.
  • Cutting telecommunications cables could disrupt internet or cable services and your ability to call 911 in an emergency.

To dig safely, excavators must first obtain a locate by contacting Ontario One Call, then follow the written instructions provided with each locate response, and follow best practices as outlined in the Canadian Common Ground Association’s (CCGA) Underground Infrastructure Damage Prevention Best Practices.

Anyone not following safe digging practices, and who hits underground infrastructure could be held liable for damages. Charges and fines could also be laid by the Ministry of Labour and the Technical Standards and Safety Authority (TSSA).

Despite these penalties, the Ontario Regional Common Ground Alliance’s (ORCGA) DIRT Report found that there were 4,940 reported damages to underground cables, pipes, and lines in 2019. 41% of the damages were caused by improper excavation practices, and 36% were caused because a locate was not requested.

Damage to underground infrastructure is preventable

Always call or click before you dig and follow safe digging practices.

Want to know more about underground infrastructure damages in Ontario?

Read the latest DIRT Report by the ORCGA.

Preventing damages and digging safely

Read the latest CCGA Underground Infrastructure Damage Prevention Best Practices.

What do the coloured marks mean?

Each type of infrastructure has an universal colour code to help identify them.
Field locates can be made in various ways including paint, stakes or flags.

Temporary Survey Markings
Temporary Survey Markings
Proposed Excavation
Proposed Excavation

Ontario One Call handles the notification for almost all of the buried infrastructure on public property (exceptions could include some first nations, provincial and federal entities.) This infrastructure is owned and maintained by organizations like public utility companies and runs through the public right of way and on to some private property up to a demarcation point, that varies from each utility owner. Public property lines differ per municipality, make sure to check your local rules.

All other buried infrastructure (including buried infrastructure beyond the demarcation point) on private property is the responsibility of the property owner to have marked.

Examples could include:

  • Gas line that goes from a house to a BBQ or pool heater
  • Lights or signs on the property
  • Electrical lines going out to sheds or a detached garage
  • Sewer and septic tanks, systems and piping
  • Security cameras

This image shows some examples of properties with public infrastructure shown in solid lines and private infrastructure shown in dashed lines.

To get your private lines marked, a competent private locator must be hired.

Sewer Safety Inspection

It’s rare, but it is possible, that a natural gas line was unintentionally installed through a sewer line. Be safe, if you have a backed up sewer call Ontario One Call at 1-800-400-2255 before you or a plumber attempts to clear the line.


What is a cross bore?
A cross bore is an unintended intersection of an existing underground utility such as a sewer or septic line by a natural gas line. This happens when utilities are installed using trenchless installation techniques such as directional drilling or boring.

Because the drilling operator can’t see the head of the equipment or other buried utilities during installation, they rely 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 type of aid to allow them to be located from above ground.

Since the identification of the cross bore risk, utilities have implemented practices to eliminate the potential risk of creating new cross bores.

Does this affect me?
Instances of natural gas lines intersecting sewer lines are rare but they have been found across Ontario. Cross bores may be present for years with no indication or immediate hazard prior to a sewer blockage. However, once clearing equipment is used outside the walls of a building, there is potential for this equipment to damage a gas line. If the gas line is damaged through sewer cleaning activity, natural gas may enter the sewer line and pose an immediate safety risk. A cross bore has the potential to exist even if there is no gas service to a property.

When should I call?
The most important thing you can do is have yourself or your plumber call Ontario One Call at 1-800-400-2255 and request a FREE sewer safety inspection before using mechanical clearing/cutting or high-pressure water jetting equipment to try to clear a blockage outside 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 available 24/7 and treated as emergency calls with a goal of resolving the issue as quickly as possible.

What happens once I call?
Once the call is placed, Ontario One Call will notify the service provider in your area who will attend and to verify if you do or do not have a cross bore on your property. If there is no potential of a cross bore, clearing activities will proceed. If there is a potential cross bore the call will be escalated to the appropriate utility.

Is there any cost to me?
No, the inspections performed are FREE.

Alternative Locate Agreement – for contractors and underground infrastructure owners

Buried infrastructure owners wishing to opt out of notification from a certain excavator for specific types of work/method of digging may wish to set up special arrangements with the excavator through an Alternate Locate Agreement or Suppression.

An Alternate Locate Agreement (ALA) advises the excavator that a traditional field locate from the Ontario One Call member is not required. This could be for work that is deemed low-risk to the member’s infrastructure (i.e. hand digging tree roots, vacuum excavation, etc.). When the excavator contacts Ontario One Call using a special Contractor ID, the member in question does not receive the locate request instead the notification system will advise the excavator that traditional field locates will not be completed under their ALA.

An ALA has to be pre-arranged with an owner of buried infrastructure (Member). The member will contact Ontario One Call to request a Contractor ID to be associated with an ALA.