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Explosion or fire due to rupture of cross bored natural gas lines

What is the potential risk?

There is a risk of explosion and/or fire in sewer and storm lines if a gas line in a cross bore is inadvertently ruptured. This can pose a serious threat to the safety of workers. Cross bores occur when horizontal directional drilling results in natural gas lines being unintentionally installed through existing utilities, such as sewer and storm lines.

Activities such as flushing out blockages and excavating around cross-bored sewer or storm lines may rupture the cross bore, causing it to leak gas. If the gas accumulates and is ignited, it may cause an explosion, potentially resulting in worker injury or death.

Ruptured cross bores have been the cause of explosions causing death in jurisdictions outside of B.C.

The locations of cross bores in B.C. may not be well documented. This means that workers may be performing at-risk activities near cross bores without their knowledge. Those at risk may include municipal or private contractors who clear sewer and storm lines, and construction, excavation, and plumbing workers working on or around cross-bored utility lines.

What industries may be at risk?

  • Local government
  • Sewer cleaning services
  • Plumbing; Excavation

How can I reduce the risk in my workplace?

As an employer, you need to know if there is the potential for the risk identified in this advisory to be present in your workplace. It’s your responsibility to regularly inspect your workplace, and to ensure that your safety procedures and practices control the risk. The following information highlights some of the sections of the Occupational Health and Safety (OHS) Regulation and Guidelines that are most relevant to this risk.

Part 20 of the OHS Regulation requires that, before excavating or drilling with powered tools and equipment, the location of all underground utility services in the area must be accurately determined, and any danger to workers from those utility services must be controlled.

In addition, excavation or drilling work in proximity to an underground utility service must be undertaken in conformity with the requirements of the owner of that utility service.

Where can I find resources?

You can access the following resources on

Publication Date: Jan 2015 Asset type: Risk Advisory Reference: RA 2015-04