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

Under the Occupational Safety and Health Act, each employer is responsible for protecting its own employees, and OSHA's multi-employer citation policy allows citations against the creating, exposing, correcting and controlling employers on a site. A general contractor that controls the site can be cited for a trench hazard even if a subcontractor dug the trench. Workers have the right to report hazards and to refuse work that poses an imminent danger of death or serious injury when there is no time to get the hazard corrected through normal channels.

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

Canada's provinces each regulate excavations under their own construction or OHS regulations. Ontario's rules, in Part III of O. Reg. 213/91, require support for trench walls deeper than 1.2 m, a clear area 1 m wide at the edge and engineered support for trenches deeper than 6 m. Alberta's OHS Code, Part 32, uses a 1.5 m threshold and an 8 m limit on distance to an exit. Canadian provinces also run one-call centers similar to 811. Workers who move between the two countries need to retrain on the numbers, because almost none of them match.

The rest of this section summarizes the US framework in more detail.

• OSHA 29 CFR 1926.650 defines terms, including competent person, protective system and trench.
• 1926.651 sets general requirements: surface encumbrances, underground installations, access and egress, exposure to vehicles and falling loads, warning systems for mobile equipment, hazardous atmospheres, water accumulation, stability of adjacent structures, protection from loose rock and soil, inspections and fall protection.
• 1926.652 requires a protective system for every excavation 5 ft or deeper unless it is made entirely in stable rock, and requires excavations 20 ft or deeper to have a protective system designed by a registered professional engineer.
• Appendix A sets out soil classification into stable rock and Types A, B and C.
• Appendix B gives maximum allowable slopes and benching configurations, Appendix C gives timber shoring tables, Appendix D gives aluminum hydraulic shoring tables, Appendix E illustrates alternatives such as trench shields, and Appendix F is a selection flow chart.

State-plan states such as California, Washington, Oregon and Michigan run their own programs, which must be at least as effective as federal OSHA and sometimes go further. California, for example, requires an annual permit from Cal/OSHA before employees enter trenches or excavations 5 ft or deeper.

Underground utility protection is mainly a matter of state law. Every state has a one-call or damage prevention statute requiring excavators to call 811 before digging, setting how long they must wait, how long marks remain valid and how close they may dig with power equipment. The federal Pipeline and Hazardous Materials Safety Administration (PHMSA) can enforce damage prevention requirements against excavators near interstate pipelines in states whose enforcement programs it finds inadequate, under 49 CFR Part 196.

The competent person

OSHA 1926.650 defines a competent person as one who is capable of identifying existing and predictable hazards in the surroundings, or working conditions which are unsanitary, hazardous or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them. Both halves matter: knowledge without authority is not enough, and a person with authority who cannot recognize soil types or protective system limits does not qualify. Subpart P gives the competent person specific tasks, including classifying soil, inspecting excavations daily and after rain, monitoring water removal, approving structural ramps and deciding when to test the atmosphere.

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

OSHA can issue citations with penalties adjusted for inflation each year. In 2025, the maximum was more than $16,000 per serious violation and more than $165,000 per willful or repeat violation. Under the trenching National Emphasis Program, inspectors are expected to initiate inspections whenever they observe an open trench or excavation, whether or not a complaint was filed. A willful violation that causes a death can be referred for criminal prosecution, and several states have charged employers with manslaughter after trench deaths. Civil lawsuits, insurance costs, project delays and debarment from public contracts follow serious incidents as well.

The right to refuse

OSHA recognizes a worker's right to refuse work when there is a reasonable belief of imminent danger of death or serious harm, the worker has asked the employer to correct the hazard, there is no time to fix it through normal enforcement channels, and the refusal is made in good faith. Section 11(c) of the Act protects workers from retaliation for reporting hazards. An unprotected trench deeper than 5 ft is a textbook imminent danger, and OSHA inspectors treat it as one.

A culture that welcomes refusals and stop-work calls is worth more than any rule. Foremen who thank a laborer 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

OSHA inspectors and courts look for written evidence that an excavation was planned and controlled. Documents commonly expected at the excavation include the 811 ticket and utility responses, any private locate records, the soil classification and the basis for it, the tabulated data for any shield or hydraulic shoring in use, any registered professional engineer's design, inspection records, atmospheric test results where testing is needed, and training records for the competent person and crew. The standard specifically requires tabulated data and engineer designs to be kept at the jobsite while the system is in use. Keeping these in a single site binder or digital folder 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.