Excavation Safety Requirements Under O. Reg. 213/91

This article is general guidance based on publicly available Ministry of Labour information. It does not replace the Occupational Health and Safety Act, O. Reg. 213/91, or legal advice. Always confirm current requirements with a qualified safety professional or the Ministry directly.

Excavation work looks routine right up until it isn't. Most trench cave ins in Ontario don't happen on large infrastructure projects. They happen on small, short duration jobs: a water service connection, a sewer repair, a foundation fix. That's exactly the kind of work where a crew is tempted to skip a step because it will only take an hour. O. Reg. 213/91 exists because that hour is when people get hurt.

This article breaks down what the regulation actually requires, in plain terms, for anyone planning, specifying, or supervising excavation work in Ontario. That includes municipal project managers, engineers, developers, and contractors.

What Is O. Reg. 213/91?

O. Reg. 213/91 is Ontario's Construction Projects regulation, made under the Occupational Health and Safety Act (OHSA). It sets the legal requirements for construction activities across the province. Part III of the regulation deals specifically with excavations and trenching, and it applies to all excavating and trenching operations, not just large civil projects. A short residential water line repair is covered by the same rules as a municipal trunk sewer installation.

It's worth knowing that "excavation" and "trench" aren't interchangeable under the regulation. An excavation is any hole left in the ground as a result of removing material. A trench is a specific type of excavation where the depth exceeds the width. That distinction matters because some requirements, like certain support system rules, apply specifically to trenches.

Understanding these requirements matters whether you're writing the tender, supervising the crew, or stepping into the trenching and excavating work yourself.

Who Must Comply?

Responsibility under O. Reg. 213/91 isn't limited to whoever is operating the equipment. The regulation and OHSA place specific duties on:

Constructors - Responsible for project level notifications, including a Notice of Project where required, and for engaging a professional engineer when adjacent structures could be affected.

Employers - Responsible for locates, soil classification, choosing the correct protective system, and making sure workers are properly trained and supervised.

Supervisors - Responsible for making sure workers comply with the regulation on site, and for flagging known hazards before work begins.

Workers - Responsible for using required protective equipment, working in compliance with the regulation, and reporting hazards.

Engineers -Required where a support system needs to be engineered, or where excavation could affect an adjacent structure.

Contractors - Responsible for day to day execution in line with all of the above, including daily inspections by a competent person.

Key Excavation Safety Requirements Under O. Reg. 213/91

1. Locate Underground Utilities Before Excavation

Before any excavation begins, the employer has to make sure all gas, electrical, and other services in and near the work area are located and marked. If a located service poses a hazard, it has to be shut off and disconnected before digging starts. If it can't be disconnected, the utility owner has to be asked to supervise the excavation while that service is uncovered.

This applies no matter what method is used to dig. Mechanical excavation, hydrovac excavation, and ploughing all fall under the same locate requirement.

2. Classify Soil Before Excavation

The regulation defines four soil types, and the type present determines how much protection a trench wall needs. Soil is classified by physically and visually examining the excavation wall, extending out a horizontal distance equal to the excavation's depth. Where more than one soil type shows up at the same location, the classification defaults to whichever type needs the most protection.

This isn't a one time check. Rain, snowmelt, or nearby water overflow can change soil stability partway through a project, which is part of why inspections have to continue throughout the work, not just at the start.

3. Protect Workers from Cave-ins

Once a trench reaches 1.2 metres in depth, protective measures become legally required. Ontario recognizes three basic methods:

Sloping - Cutting trench walls back at an angle, away from the excavation.

Shoring - Timber or hydraulic supports that hold the walls in place.

Prefabricated support systems - Trench boxes and shields.

No worker may enter a trench deeper than 1.2 metres unless the walls are sound rock, properly sloped, shored, or protected by one of these systems. Depending on depth and soil conditions, some support systems are required by regulation to be designed by a professional engineer.

There's also a separate fall protection requirement. If an excavation doesn't meet the regulatory slope requirements and is more than 2.4 metres deep, a barrier at least 1.1 metres high has to be placed at the top to stop workers or bystanders from falling in.

4. Keep Excavations Free of Water

Water changes everything about soil stability. Excess water has to be removed from an excavation, and trenches should be checked again after rainfall, snowmelt, or any nearby water event, since these can quickly weaken a wall that was stable the day before.

5. Maintain Safe Access and Egress

Workers need a safe way in and out of an excavation. That could be a ladder, steps, a ramp, or another approved method. In a trench, ladders have to sit within the area protected by the support system, so they're actually usable if a collapse happens. And no one works in a trench alone. Another worker has to be positioned above ground, close to the trench or its access point, whenever someone is working below.

6. Control Spoil Piles, Equipment, and Stored Material

There are two separate distance rules here, and they're easy to mix up.

Heavy equipment, excavated soil, and rock have to stay at least 1 metre back from the upper edge of the excavation. This rule exists specifically to protect wall stability. Equipment can't be positioned or operated in a way that could affect the wall, and a surcharge load too close to the edge is one of the more common causes of an otherwise stable wall failing.

Separately, general construction material being stored, stacked, or piled on site can't be placed closer than 1.8 metres to an excavation, a floor or roof opening, or the open edge of a floor, roof, or balcony. This is a broader material storage rule, not limited to spoil or equipment, and it applies on top of the 1 metre setback, not instead of it.

7. Protect Adjacent Structures

If an excavation could affect a nearby building, foundation, or structure, the constructor has to bring in a professional engineer, who must specify in writing what precautions need to be taken. This isn't left to judgment on site. It's a written engineering requirement.

8. Daily Inspection Requirements

Every excavation has to be inspected by a competent person, a specific legal term under OHSA, before workers enter, and again whenever conditions change. A trench that was fine Monday morning still needs a fresh check Tuesday, and again after a heavy rain, and again if the soil starts to look different than it did an hour earlier.

Common Excavation Safety Mistakes

Most incidents don't come from one dramatic failure. They come from small procedural gaps that stack up:

• Assuming locate markings show utility depth, when locates confirm presence and approximate position, not exact depth

• Classifying soil once at the start and never rechecking after a rain event

• Positioning equipment or spoil closer than the required 1 metre setback from the trench edge, or stacking material inside the 1.8 metre general storage limit

• Poor spoil pile management that adds uncontrolled weight near the excavation

• Using inadequate or no trench protection on a dig assumed to be too small to matter

• Continuing work in a water filled excavation instead of pausing to remove the water first

• Sending a worker into a trench without another worker stationed above ground

• No documented daily inspection by a competent person, or no re-inspection after a clear change in conditions

Every one of these is preventable with planning, not extra equipment.

How Hydrovac Excavation Supports Compliance

Hydrovac excavation doesn't replace any of the requirements above. Locates, soil classification, and protective systems still apply no matter which method is used. What hydrovac does is support safer execution of those requirements in specific situations.

Because hydrovac exposes utilities with pressurized water and vacuum extraction instead of mechanical contact, it's commonly used to daylight a service before mechanical excavation begins nearby, which lowers the risk of a utility strike in congested corridors. It's also a standard method for potholing ahead of horizontal directional drilling work, confirming exact utility location and depth before a bore path is finalized. In both cases, it's a tool that supports safer excavation practices. It isn't a substitute for locates, soil assessment, or trench protection.

Excavation Safety Checklist

Before excavation begins, confirm:

• Locates are current, valid, and cover all utilities in and near the work area

• Soil type has been classified by a competent person, including the required horizontal distance from the wall

• A protective system (sloping, shoring, or trench box) is in place for any trench over 1.2 metres

• The excavation is free of standing water, or there's a plan to remove it

• Safe access and egress (ladder, ramp, or steps) is positioned within the protected area

• Heavy equipment and excavated material are kept at least 1 metre from the excavation edge, and other stored materials respect the 1.8 metre general limit

• A professional engineer has reviewed the plan if adjacent structures could be affected

• A worker is stationed above ground whenever anyone is working in the trench

• A competent person has completed and documented today's inspection

• A Notice of Project or Notice of Trench Work has been filed if the project meets the threshold

Conclusion

Compliance with O. Reg. 213/91 isn't just a legal obligation. It's one of the most direct ways to reduce the risk of a serious incident on an excavation site. Locating utilities properly, classifying soil accurately, choosing the right protective system, and inspecting the work daily aren't separate boxes to check. They work together, and skipping one tends to undermine the rest. Good planning before the first shovel goes in the ground is still the most reliable safety measure there is.

Safety isn't an afterthought for our crews. It's part of how we plan every excavation, and we're currently working toward COR certification to formalize that commitment further. You can read more about our approach on our Health and Safety page.

FAQs

Q1. What is O. Reg. 213/91? 

O. Reg. 213/91 is Ontario's Construction Projects regulation under the Occupational Health and Safety Act. It sets legal requirements for construction activities, including a dedicated section covering excavation and trenching safety.

Q2. Who is responsible for excavation safety? 

Responsibility is shared across the constructor, employer, supervisor, and workers. Professional engineers carry added duties where support systems or adjacent structures are involved.

Q3. When is trench protection required?

Trench protection is required once a trench reaches 1.2 metres in depth. Sloping, shoring, or a trench box must be in place before anyone can enter.

Q4. Do utility locates show depth? 

No, not reliably. Locates confirm the presence and approximate horizontal position of a utility, not its exact depth. Depth should be confirmed through safe exposure, such as hydrovac daylighting, rather than assumed from a locate mark.

Q5. What is a competent person? 

A competent person is a specific legal term under the Occupational Health and Safety Act. It refers to someone qualified through knowledge, training, and experience to organize the work, who is familiar with the Act and applicable regulations, and who understands the potential hazards in that workplace.

Q6. When is hydrovac excavation recommended? 

Hydrovac excavation is commonly recommended to expose utilities safely ahead of mechanical excavation, particularly in congested corridors or where locate information is unclear, and for potholing ahead of HDD work.

Q7. How often should excavations be inspected? 

Excavations should be inspected before workers enter each day, and again any time conditions change, including after rainfall, snowmelt, a nearby water event, or any visible change in the soil.

Q8. Can work continue after heavy rainfall? 

Not without a fresh inspection first. Water significantly affects soil stability, so excavations should be re-inspected by a competent person and cleared of standing water before work resumes.