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Hazard alert – collapse of excavations, trenches, tunnels and shafts

Date posted: 2022-07-12

Over the last several years, Manitoba construction sites have experienced collapses of excavations, trenches, tunnels and shafts at depths of three metres or greater. Collapses have great potential for harm and have resulted in serious injuries and fatalities. During the investigations into these incidents, it was found that the walls of the excavations had not been stabilized using a method designed and certified by a professional engineer.

How collapses occur

When earth is removed from the ground it creates an opening, and the remaining earth surrounding the opening tends to relax. This increases the pressure towards the walls of the opening and makes the ground collapse. Water in the soil or ground also affects the stability of the walls by putting additional pressure on the walls and increasing the possibility of a cave-in. Victims buried in an excavation collapse may suffocate because of the pressure exerted by the soil on their bodies, or sustain severe crushing injuries.

Prevention measures

Employers must take into account the proposed depth of an excavation and ensure that when required, the walls of an excavation, trench, tunnel or ​shaft are stabilized using a method designed and certified by a professional engineer before allowing workers to enter, as outlined in Part 26.15(4), Part 26.15(5), Part 26.16(2), Part 26.14(4), Part 26.18(1), Part 26.28(1) and Part 26.33(1) of the Workplace Safety and Health Regulation.

Other related safety information are available at the following links:

SAFE Work Manitoba remind​​​s employers that their responsibilities also include:

  • developing safe work procedures, training workers in the procedures, and ensuring workers follow the procedures for the work to be done at an excavation, including installation, use and removal of shoring
  • notifying the Workplace Safety and Health Branch that they intend to perform excavation work and receive a registration number from the branch before beginning excavation work
  • ​designating a competent person to supervise work at the excavation site, whenever a worker is in the excavation or work on the excavation is being performed.

Workers’ responsibilities include:

  • following the safe work procedures developed for the workplace, and using all necessary equipment and personal protective devices when entering or working in an excavation, trench, tunnel or shaft.

Industry-based safety programs (IBSPs)

If you have questions about this topic that are specific to your industry, please contact your industry-based safety program (IBSP).

If your industry is not currently associated with an IBSP, you’re unsure whether your industry has an IBSP or you have more general questions, please contact SAFE Work Manitoba.





About the WCB

The Workers Compensation Board of Manitoba serves workers and employers through a no-fault insurance system integral to the Manitoba economy. Funded collectively by employers, the WCB promotes safe and healthy workplaces, facilitates recovery and return to work, delivers compassionate and supportive compensation services to workers and employers, and ensures responsible stewardship of Manitoba's workers' compensation system.