The Locate Marks Are Not Where the Pipe Is

The paint on the ground is not the pipe. It is the centre of a tolerance zone, and the actual buried facility can be anywhere within roughly one metre on either side of those marks.

That single misunderstanding accounts for a large share of utility strikes. An operator lines a bucket up beside the orange line, keeps a respectful-looking gap, and puts the teeth through a gas service that was sitting eighty centimetres off where the paint said.

The hand expose zone

Canadian damage prevention practice gives that margin a name and a rule. WorkSafeBC's guide to preventing damage to buried facilities defines the hand expose zone as the distance one metre either side of the locate marks.

Inside that zone, mechanical excavation is not permitted until the facility has been physically exposed by hand. Ontario's guidance puts it the same way: within the tolerance zone you dig first with hand tools to expose hidden pipes before any machinery goes in.

Soft digging methods are the accepted alternatives. Hand digging with a shovel or spade, and potholing using vacuum excavation with water or air to open small holes above the line, both expose the facility without the force that damages it.

Alberta's damage prevention process uses the same concept under the same name, and notes the hand expose zone can be wider than the standard distance for certain pressure categories.

One important exclusion in BC: the one metre hand expose zone applies to all buried facilities except high-pressure pipelines, which carry their own and more demanding requirements. If a high-pressure line is in your dig area, the standard rule is not the rule.

Notice periods differ by province

The one-call system is free, funded by the utility owners, and it is the mechanism by which every buried facility owner in your dig area gets told you are coming.

How much warning you have to give depends where you are. British Columbia asks for a locate request at least three working days before digging. Ontario requires no less than five business days, and there it is a legal requirement rather than good practice.

Each province has its own centre: BC 1 Call, Utility Safety Partners in Alberta, Sask 1st Call, Ontario One Call, Info-Excavation in Quebec and New Brunswick, and others. The national portal at clickbeforeyoudig.com routes you to the right one.

Submitting the request is quick and the result is a ticket number. Keep it. Utility owners commonly ask for it, and it is the record that the request was made and when.

The volume gives a sense of how normal this is rather than exceptional: BC 1 Call issued more than 200,000 locate tickets in a single year.

Locates expire, and so does paint

This is the administrative failure that catches jobs running longer than planned.

A locate is valid for the dates on the ticket. If your project extends beyond them, you need a new request rather than carrying on with the old markings.

The physical marks fade independently of the paperwork. Paint washes off, flags get pulled out or run over, and a week of rain on an unpaved site can remove them entirely. Where the marks have disappeared or you are no longer confident of them, request a re-locate rather than working from memory.

Photograph the marks when they are fresh. It costs nothing, it preserves the layout if the paint goes, and it is useful evidence if a dispute arises later about what was marked.

Emergency locate requests exist for genuine emergencies, such as a repair needed to correct a hazardous situation. They are not a shortcut for poor planning, and using them that way erodes a service everyone depends on.

A nick counts as damage

Most crews know to report a strike that breaks a line. Far fewer report the ones that do not.

The guidance is explicit and broader than people assume: notify the facility owner immediately if you contact, scrape, dent, nick or otherwise damage any underground line or cable. The absence of a leak, a spark or a loss of service does not mean the facility is undamaged.

The reason is delayed failure. A scraped coating on a steel pipe starts corroding at that point. A nicked cable jacket lets moisture in. The consequence arrives months or years later, often to somebody who had nothing to do with the dig.

Reporting also protects the crew that caused it. A documented contact reported at the time is a different conversation from a failure traced back to an unreported scrape.

Where there is an actual strike involving gas or electrical, the sequence is different again: get people clear, do not attempt to repair or pinch off anything, keep ignition sources away, and call emergency services and the utility owner. Our guide to CSA Z1220 first aid kit requirements covers on-site provision for the injuries that can follow.

What the colours mean, and what they do not

Canadian marking follows a universal colour code, and knowing it is useful for everyone on a site rather than only the person who requested the locate.

Red marks electrical power. Yellow marks gas, oil and steam. Orange marks communications and cable. Blue marks potable water. Green marks sewer and drain. Purple marks reclaimed water and irrigation. White marks the proposed excavation itself, and pink marks temporary survey.

What the colours do not tell you is depth. There is no reliable standard burial depth for most services, and lines get shallower over time through erosion, regrading and resurfacing. A service that was buried to spec in 1985 may be much closer to the surface now.

They also do not cover privately owned facilities. One-call members are the registered utility owners, and the lines a previous property owner ran to a shed, a pump, a light standard or an irrigation system are nobody's responsibility to mark. Those have to be identified separately, often by private locating.

And marks only cover what the request described. A locate requested for one corner of a site does not cover the trench someone decided to extend on Thursday.

Where this meets the trench

Utility strikes and excavation collapses are the same job with two different ways of going wrong, and the controls interact.

Previously disturbed ground around a buried service behaves differently from undisturbed soil, which matters for wall stability as much as for locating. A trench that follows an old service run is being cut through backfill.

Exposed services inside an excavation then need supporting rather than left spanning the void, and they become an additional hazard for anyone working in there: an energized cable or a live gas line at shoulder height in a confined trench.

Electrical contact underground carries the same consequences as overhead contact, and footwear certification is part of the picture without being a substitute for isolation. Our guides to work boots for electricians and CSA work boot symbols cover the omega mark and the fact that its protection degrades with wear and moisture.

Ground conditions underfoot in and around an open excavation are their own hazard, covered in our guides to slip resistance at work and work boots for concrete workers.

The site around the dig

Most ground disturbance in populated areas happens next to traffic, pedestrians or both, which brings a second set of controls.

Conspicuity for the crew matters because excavation work puts people at road level beside moving vehicles, covered in our guides to CSA Z96 classes and levels and traffic control person equipment.

Head protection applies for anyone working below grade or near operating equipment, covered in our hard hat safety guide.

Winter adds its own complication: frozen ground tempts crews toward heavier equipment and more force, exactly when hand exposing is hardest. It also hides marks under snow. Our guide to cold stress at work in Canada covers the exposure side of winter digging.

We do not sell vacuum excavation equipment, locating instruments or marking paint. Those come from equipment suppliers and locating contractors. For the wider kit see the complete PPE checklist for Canadian workers, our guide to PPE requirements for Canadian construction sites, our guide to who pays for PPE in Canada and our guide to CSA certified versus CSA compliant.

Frequently Asked Questions

How accurate are locate marks?

They identify a zone rather than a line. The buried facility can be anywhere within roughly one metre on either side of the paint or flags, which is why that area is called the tolerance zone or hand expose zone. Treating the marks as the exact position of the pipe is the most common cause of strikes.

Can I use a machine near the marks?

Not inside the hand expose zone until the facility has been physically exposed. Hand digging with a shovel or spade, or potholing with vacuum excavation using water or air, are the accepted methods for exposing it. Machinery goes in only after the line is visible.

How far in advance do I need to request a locate?

It depends on the province. British Columbia asks for at least three working days; Ontario requires no less than five business days and treats it as a legal requirement. The service is free in both cases, funded by the utility owners, and the national portal routes you to your provincial centre.

Do locates expire?

Yes. A locate is valid for the dates on the ticket, and work extending beyond them requires a new request. Markings also disappear physically through weather and traffic, so request a re-locate rather than working from memory or from a faded line.

Do I have to report a scrape that did not cause a leak?

Yes. Guidance is to notify the facility owner immediately if you contact, scrape, dent, nick or otherwise damage a line or cable, regardless of whether service was interrupted. Damaged coatings and jackets fail later, and an unreported contact becomes someone else's emergency.

Does a locate cover private underground lines?

No. One-call centres notify registered utility owners. Privately installed services, such as lines to a shed, pump, light standard or irrigation system, are not covered and need to be identified separately, often through a private locating service.

This guide is general workplace safety information and is not training. Ground disturbance requirements, notice periods, tolerance zone distances and damage reporting obligations are set by provincial legislation and by the facility owners, and differ between jurisdictions and facility types. High-pressure pipelines carry additional requirements. Confirm yours with your provincial one-call centre and the occupational health and safety authority that governs your workplace before any ground disturbance.