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Excavation Hazards Focus of Blitz

Inspectors will target excavation hazards during a province-wide blitz in May 2014.

The increased enforcement is part of the province’s Safe At Work Ontario enforcement initiative, launched in June 2008.

The Ministry of Labour inspectors will visit construction projects where excavation activities and short-term trenching operations are taking place.

Excavations are holes in the ground created as a result of removing material. Generally, an excavation is dug in the earth to install utilities such as sewers, watermains and gas supplies, and to construct foundations for buildings or other structures. This includes excavations of trenches along existing right of ways on roads.

Inspectors will check that employers, supervisors and workers are complying with requirements under the Occupational Health and Safety Act and its regulations.

Workers can be seriously injured or even die as a result of hazards involving excavation activities.

If an excavation collapses, a trapped worker may die before a rescue can begin because even being covered with small amounts of soil can result in a worker’s inability to breathe. As well, a successful rescue may be impossible due to the soil’s heavy weight.

Between 2008 and 2013, 12 workers died and 33 workers were critically injured in excavation and trenching incidents at construction projects in Ontario.

Excavation activities include:

  • “trenching” a narrow excavation where the excavation depth exceeds the excavation width –generally used to install or repair services such as natural gas, electrical, telecommunications and sewers
  • construction of foundations
  • soil retention (stabilizing soil while digging basements for larger buildings)
  • construction of footing (supports) for the construction of buildings or bridges
  • road construction and utility repairs involving excavation
  • digging out caissons (large watertight chambers) to support structures in certain ground conditions

Excavation Hazards

Construction workers are at risk of injury due to:

  • falls into a trench or excavation
  • tripping over equipment
  • sudden collapse of unsupported excavation walls
  • excavated material or other objects falling on workers
  • exposure to underground services or overhead electrical cables
  • unstable nearby structures such as other buildings
  • mishandled or poorly placed materials
  • hazardous atmospheres (noxious gases/lack of oxygen)
  • toxic, irritating or flammable and explosive gases
  • incidents involving vehicles and other mobile equipment

Blitz Focus

Ministry inspectors will visit a range of construction projects where large excavation operations are taking place. In particular, ministry inspectors will visit project types and employers:

  • with a high incidence of lost-time injuries involving excavation workers
  • not previously visited by the ministry
  • where complaints have been received and
  • where there is a history of non-compliance

Inspectors will take enforcement action, as appropriate, in response to any violations of the Occupational Health and Safety Act and its regulations.


Inspectors will focus on the following key priorities:

Excavation wall support: Inspectors will check that:

  • excavation and trenching support systems are in place
  • employers are determining the site’s soil type to ascertain the strength and stability of the excavation walls
  • trench and excavation walls are being stripped of any loose rock or other material that could slide, roll or fall on a worker
  • constructors are taking appropriate precautions to prevent damage to nearby structures, including employing a professional engineer to specify in writing any precautions to be taken
  • there is safe access and egress available to workers
  • no workers are working alone

Utilities locations: Inspectors will check that:

  • employers identify, locate and mark utilities to prevent worker contact with gas lines, electrical conductors and other services during excavations
  • utility owners have been requested to supervise the uncovering of potentially hazardous utilities if the services cannot be disconnected during the excavation

Safety measures: Inspectors will check that:

  • employers have measures and procedures in place to prevent slips, trips and falls hazards
  • a barrier at least 1.1 metres in height is provided, when required, at the top of an excavation if it does not meet regulatory slope requirements and is more than 2.4 metres deep
  • a clear work space of at least 450 millimetres is maintained between the excavation’s wall and any work platform
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