Law, responsibilities and the competent person

Excavation is one of the most heavily regulated activities on a construction site, because the hazards are well understood and the controls are well known. When a trench collapses, investigators rarely find a hazard nobody could have foreseen. They find a rule that was not followed. This lesson sets out who is responsible for what, the main legal requirements, and the role of the competent person who makes day-to-day decisions about the excavation.

This lesson summarizes the law for training purposes. Always work from the current regulation in your jurisdiction and your employer's procedures, and ask when the two seem to conflict.

The duty holders

Canadian occupational health and safety statutes assign duties to several parties on a construction project. In Ontario, the Occupational Health and Safety Act (OHSA) assigns duties to the owner, the constructor, employers, supervisors and workers. The constructor, usually the general contractor, has overall responsibility for compliance on the project. Each employer must make sure its own workers follow the regulations and are trained. Supervisors must ensure workers use the required protection and must advise them of hazards. Workers must use the equipment provided, report hazards and may refuse unsafe work. Other provinces use similar structures, sometimes calling the constructor the prime contractor, as in Alberta and British Columbia.

Owners also matter. The owner of a buried facility, whether a gas utility, a telecommunications carrier, a municipality or a pipeline company, has duties under one-call and damage prevention laws to mark its facilities accurately and on time. The owner of the land or project often decides the budget and schedule that determine whether a crew can afford to do the job safely.

The Canadian framework

In Ontario, excavation work on construction projects is governed by Part III of the Construction Projects regulation, O. Reg. 213/91, sections 222 to 242. Key requirements include:

• Section 225: work may not be done in a trench unless another worker is working above ground in close proximity.
• Section 226 and 227: the soil must be classified as Type 1, 2, 3 or 4, by examining the walls and the ground within a distance from the excavation equal to its depth.
• Section 228: gas, electrical and other services in and near the excavation must be located and marked before excavation begins, and hazardous services shut off or uncovered under the owner's supervision.
• Section 230: excavations a worker may enter must be kept reasonably free of water.
• Section 233: a level area at least 1 m wide must be kept clear of equipment, spoil, rock and construction material along each wall, and a barrier at least 1.1 m high is needed where a person could fall more than 2.4 m into an excavation with unsloped walls.
• Section 234: the walls of an excavation must be supported by a support system unless an exemption applies. Exemptions include excavations less than 1.2 m deep, excavations in sound rock, walls sloped according to the soil type, and excavations where a professional engineer gives a written opinion that the walls are stable.
• Section 235: a trench deeper than 6 m or wider than 3.6 m needs a support system designed by a professional engineer for that location.

Alberta's OHS Code, Part 32, applies a 1.5 m depth threshold for protective structures, requires a safe exit within 8 m of a worker in a trench deeper than 1.5 m, keeps spoil piles at least 1 m from the edge, and requires protective structures deeper than 3 m to follow a professional engineer's specifications. It also contains detailed rules for locating buried facilities and a hand expose zone around them, covered in lessons 3 and 4. British Columbia's OHS Regulation, Part 20, uses a 1.2 m threshold. Federally regulated work, such as federal pipelines and railways, falls under the Canada Labour Code and, for work near federally regulated pipelines, the Canadian Energy Regulator's damage prevention regulations.

The competent person

Excavation rules depend heavily on the judgment of a knowledgeable person on site. Ontario's OHSA defines a competent person as one who is qualified because of knowledge, training and experience to organize the work and its performance, is familiar with the Act and regulations that apply to the work, and has knowledge of any potential or actual danger to health or safety in the workplace. O. Reg. 213/91 also refers to competent workers, for example to inspect an excavation as often as an engineer's opinion specifies. Supervisors of excavation work are normally expected to meet the competent person standard.

In practice the competent person for an excavation should be able to:

• Classify soil using visual and manual tests and recognize when conditions change.
• Select a protective system and know its limits, including manufacturer's tabulated data for shields and hydraulic shores.
• Recognize when an engineer is needed.
• Inspect the excavation, the protective system and the surrounding area, and document the inspection.
• Stop work and remove workers when conditions are unsafe, without needing someone else's permission.

Being the most senior person present, or the operator with the most years in the seat, does not make someone competent. The designation belongs to a person whose training and knowledge can be shown, and whose authority to stop work is real.

Enforcement and consequences

Inspectors can issue orders to stop work, require engineering assessments and lay charges. In Ontario, the maximum fine for a corporation convicted under the OHSA is $2 million per count, and directors and officers face up to $1.5 million and possible imprisonment; individuals such as supervisors face fines of up to $500,000 and up to 12 months in jail. Courts in Ontario have imposed large fines after trench deaths, and the Criminal Code's Westray amendments (section 217.1) make it a legal duty for anyone who directs work to take reasonable steps to prevent bodily harm, with criminal negligence charges possible after a death. Workers' compensation premiums, project delays and lost bids follow serious incidents as well.

The right to refuse

Every Canadian jurisdiction gives workers the right to refuse work they have reason to believe is dangerous. In Ontario the refusal process under section 43 of the OHSA starts with reporting to the supervisor, who investigates with the worker and a worker representative; if the worker still has reasonable grounds, an inspector is called. Workers may not be disciplined for a refusal made in good faith. An unprotected trench that requires protection is a textbook example of work that can be refused.

A culture that welcomes refusals and stop-work calls is worth more than any rule. Foremen who thank a labourer for refusing to enter an unshored trench, rather than sending someone else, create crews that speak up before people get hurt.

Documents that should be on site

Regulators and courts look for written evidence that an excavation was planned and controlled. On an Ontario project, the documents commonly expected at the excavation include the locate sheets and any private locate records, the soil classification and the basis for it, the drawings and tabulated data for any prefabricated or hydraulic support system, any professional engineer's written opinion or design, inspection records, atmospheric test results where testing is needed, the emergency procedures and training records for the workers involved. Keeping them in a single site binder or digital folder, rather than scattered between the office and the truck, means the supervisor can answer an inspector's questions on the spot and the crew can check the limits of the equipment they are using.

Training records deserve particular attention. A competent person designation is only as good as the evidence behind it: course certificates, documented field experience, and a written appointment that states the person's authority to stop work. Crews should also have documented instruction on the specific protective system in use, because a worker who has never been shown how a hydraulic shore is installed or why the box must stay in contact with the work cannot be expected to use it correctly.