Disclaimer: This resource has been prepared to help the workplace parties understand some of their obligations under the Occupational Health and Safety Act (OHSA) and regulations. It is not legal advice. It is not intended to replace the OHSA or the regulations. For further information please see full disclaimer.
Hazards involving excavations, in particular trenches, can lead to serious incidents involving workers at construction sites.
Workers can be critically injured or die in cave-ins. Many cave-ins occur on small jobs of short duration, such as water, gas, electrical and sewer line connections.
A constructor is required to complete a Notice of Project when:
A Notice of Trench must be given in person or by phone or fax for a trench if section 6 of Construction Regulation does not apply, and the project includes digging a trench more than 1.2 metres deep (47 inches) and may be entered by a worker. [Construction Reg. s. 7]
Mark and locate utilities: Employers must ensure all gas, electrical and other services are located or marked in or near the area to be excavated. If a service poses a hazard, it must be shut off and disconnected before the excavation activity begins. If a potentially hazardous service cannot be disconnected, the service owner must be asked to supervise the service’s uncovering during the excavation. [Construction Reg. s. 228]
Adjacent structures: Constructors must prevent damage to adjacent structures by engaging a professional engineer who must specify in writing the precautions to be taken. [Construction Reg. s. 229]
Soil strength: Determine the soil type to protect excavation walls from collapsing. This can be determined by doing things such as inspecting trenches and excavations following a rainfall, melting snow, thawing earth and overflows from nearby streams, storm drains and sewers. The soil type determines the strength and stability of the excavation walls. [Construction Reg. s. 226]
Wall stability: Strip the wall of a trench or excavation of any loose rock or other material that may slide, roll or fall on a worker. [Construction Reg. s. 232]
Equipment: Keep heavy equipment, excavated soil or rock and construction material at least one metre away from the upper edges of the trench or excavation. Do not position or operate a vehicle or machinery in a manner that could affect the wall’s stability. [Construction Reg. s. 233]
Work space: Maintain a clear work space of at least 450 millimetres (18 inches) between the wall of an excavation and any formwork, masonry or similar wall. [Construction Reg. s. 231]
Fall protection: Provide a barrier at least 1.1 metres (42 inches) high at the top if an excavation does not meet regulatory slope requirements and is more than 2.4 metres (eight feet) deep. [Construction Reg. s. 233(4)]
Protect yourself: Never enter a trench deeper than 1.2 metres (47 inches) unless the walls are sound, made of solid rock, properly sloped, shored or protected by a trench box. Never work alone in a trench.
Protective systems: Workers must be protected against trench or excavation cave-ins and other hazards using three basic methods:
"Competent person": Trenches and excavations must be inspected daily for hazards, and when conditions change, before workers enter them. This must be done by a "competent person", as defined by the OHSA.
A "competent person":
Entry and exit: Provide safe access and egress for workers at excavations by means of ladders, steps, ramps, or other safe methods of entering or exiting. Trenches must have ladders placed in the area protected by the support system and be accessible in the event of a collapse. [Construction Reg. s. 240]
Employers have a number of duties and responsibilities under the OHSA and Construction Regulations.
Some examples of employers’ duties:
Some examples of supervisors’ duties:
Some examples of workers' duties:
Call 1-877-202-0008 any time to report critical injuries, fatalities or work refusals. Monday to Friday 8:30 a.m. to 5 p.m. for general inquiries about workplace health and safety
Always call 911 in an emergency.
Disclaimer: This web resource has been prepared to assist the workplace parties in understanding some of their obligations under the Occupational Health and Safety Act (OHSA) and the regulations. It is not intended to replace the OHSA or the regulations and reference should always be made to the official version of the legislation.
It is the responsibility of the workplace parties to ensure compliance with the legislation. This web resource does not constitute legal advice. If you require assistance with respect to the interpretation of the legislation and its potential application in specific circumstances, please contact your legal counsel.
While this web resource will also be available to Ministry of Labour inspectors, they will apply and enforce the OHSA and its regulations based on the facts as they may find them in the workplace. This web resource does not affect their enforcement discretion in any way.