The clearance problem on a concrete site is almost never discovered by the person who could have solved it cheaply. It is discovered by a pump operator at seven in the morning, with a loaded truck behind him, looking at a service drop that crosses the only place the boom can set up. By then the options are all expensive: move the pump and lose reach, book a line crew and lose the day, or carry on and hope.
Alberta puts the whole subject in one short part of the Occupational Health and Safety Code — Part 17, Overhead Power Lines, sections 225 to 227 — and it is short because it does two things. It sets a distance you may not cross, and it tells you who to phone before you cross it. What catches builders is that the default distance is far larger than most people assume, and it governs the site until somebody does the work of replacing it with a smaller one.
Seven metres governs the site until the utility tells you the voltage
Start here, because this is the number that drives the schedule. Where work is done or equipment operated within 7 metres of an overhead power line, the employer must contact the line’s owner to determine the operating voltage. Until that voltage is confirmed, the clearance the site has to maintain is the full 7 metres.
Read that in the order it bites. The 7 metres is not the compliance distance; it is the trigger for a phone call and the fallback that applies while you wait for the answer. A boom that stays 7 metres clear of every conductor on the lot needs no call. A boom that cannot has created a dependency on somebody outside your company, and that dependency belongs on the schedule, not on the pour-morning tailgate.
Once the owner confirms voltage, the governing distance comes out of Schedule 4 of the Code — printed as Table 17.1 in the older explanation guide, which is why both labels are in circulation.
The real distances are mostly shorter than seven metres
Here is the schedule itself, which is worth laminating because it settles most arguments on site:
| Operating voltage between conductors | Safe limit of approach |
| 0–750 V, insulated or polyethylene-covered conductors | 300 mm |
| 0–750 V, bare uninsulated conductors | 1.0 m |
| Above 750 V, insulated conductors | 1.0 m |
| 750 V – 40 kV | 3.0 m |
| 69 kV, 72 kV | 3.5 m |
| 138 kV, 144 kV | 4.0 m |
| 230 kV, 260 kV | 5.0 m |
| 500 kV | 7.0 m |
Two things in that table matter commercially. The first is that the distribution line over a typical Calgary residential lane — the 750 V to 40 kV band — carries a 3.0 metre limit, not 7. On a tight infill, the gap between 7 and 3 metres is often the difference between a line pump and a boom pump, or between one setup and two. That is a real number on a quote, and only a crew that made the call gets to use it.
The second is that the two shortest distances come with conditions attached. The 300 mm and 1.0 metre insulated-conductor rows apply only where the conductor is insulated or covered along its entire length and built to rated, tested insulation levels. A weathered service drop that looks jacketed does not qualify on appearance, and nobody on a concrete crew can certify it. Those rows are the utility’s to confirm, not yours to assume.
If work genuinely has to happen closer than the governing distance, the Code does not simply forbid it. The employer notifies the owner before beginning work and obtains its assistance, and the owner decides what makes it safe: de-energising, relocating or isolating the line, or another equally effective measure. That is a scheduled utility visit with a lead time, which is why it belongs on the drawing-stage list.
What the 2023 amendment changed, and why generic safety content is now out of date
Part 17 was amended effective 31 March 2023. Four changes affect how a contractor runs the file, and none of them touched the distances.
The word “energized” came out of Part 17. Every overhead line is now treated as energized, which aligns the Code with how the utility industry has always worked — and closes the argument that used to happen on site about whether a line looked dead.
Workers now share the duty with the employer. Maintaining the Schedule 4 distances is no longer framed as the employer’s obligation alone, which lines Part 17 up with the worker’s general duty under the Act to take reasonable care.
The owner is not necessarily a utility. The notification duty now names an electric utility, a rural electrification association, or an industrial power producer. On acreage and county work around Calgary that is not academic — the line over the approach may belong to an REA, and the utility’s call centre is the wrong number.
The standard reference changed. Part 17 now points to CAN/ULC-S801-14 rather than the Alberta Electrical and Communication Utility Code, and the section 225 exemption is written around utility workers working to that standard. That exemption covers utility workers and tree trimmers. It has never covered a concrete crew.
Any toolbox talk or template still built on the pre-2023 wording reads as close enough and is wrong in exactly the places an officer asks about.
The equipment that reaches the lines is not the equipment people watch
The machine that makes contact is rarely the one the hazard assessment focused on. Utility Safety Partners reports that over 25 per cent of direct power line contacts in Alberta involve excavators — the machine with no obvious reason to be near a conductor, until the boom comes up to swing a bucket or the stick is raised to travel.
On a foundation or flatwork job, the reaching list is longer than most plans allow for:
- The concrete pump boom — the tallest thing on most residential pours, and usually set up by someone who arrived after the hazard assessment was signed.
- The telehandler placing form panels or rebar bundles, at full boom and full tilt.
- Scaffold erected on a wall form: conductive, and it goes up fast.
- Any crane picking gang forms or cages, where the load swings wider than the operator’s mental envelope.
- Equipment in transport, taller on the trailer than it is working, with loads taller still.
Two field effects make the geometry worse than the drawing suggests. Long spans sag and rise with temperature, so a conductor’s position in July is not its position in February. Wind swings the conductor, and swings the load too. Neither is in a clearance you measured once.
Where the operator cannot keep eyes on the line, section 191 puts a competent signaller in the frame, and that signaller’s only job is keeping the equipment beyond the limit. Not signalling and spotting the pour. One task. The related machine obligations — authorisation, pre-use inspection, the travel-path planning that keeps a boom away from the conductor in the first place — sit in Part 19, which we mapped in powered mobile equipment rules on a Calgary pour.
Line height tells you what you are looking at before anyone calls back
Minimum design heights are a useful first read on a lot, because they tell you roughly how much air you have. Under the utility code heights referenced by Part 17, lines are built to minimums that vary by what passes beneath: 3.6 m where only pedestrians normally go, 4.1 m over driveways to residences and residential garages, 4.2 m where agricultural equipment is normally used, 4.8 m over lanes, alleys and entrances to commercial or industrial premises, 5.3 m over roads and highways, and 5.4 m over an underground pipeline right-of-way.
Those are design minimums for the line, not clearances for your work, and they are why a lane-side pour deserves a second look: a conductor built to 4.8 metres over a commercial alley leaves very little room above a boom that has to clear a fence and a garage.
One narrow exemption is worth knowing. The approach distances do not apply to loads, equipment or buildings less than 4.15 metres in height while being transported beneath a line — a number that comes from commercial vehicle dimension limits, not from any judgement about safety. It covers driving under. It does not cover working under.
If a machine does make contact
Plan this before it is needed, because the instinct is wrong. Treat the equipment, the load and the ground around it as energized. Keep everyone at least 10 metres back from a downed line or a contact point, and understand that the safe distance can be considerably greater depending on voltage.
The operator’s move is to break contact by moving the equipment, if that can be done. If it cannot, the operator stays on the machine and waits for the utility — stepping down bridges machine and ground through a body. Where fire forces an exit, the technique is to jump clear with feet together, landing without touching the machine, then shuffle or hop at least 10 metres away rather than walking.
Afterwards two reporting paths run in parallel. Power line contacts and electrical accidents are reportable to Alberta Municipal Affairs, Safety Services, and the OHS reporting obligations run on their own clock — set out in serious incident reporting on a concrete site. Do not let one absorb the other.
Four things to close before equipment is mobilised
- Mark the conductors on the site plan, with voltage. One call to the line’s owner — utility, REA or industrial producer — turns an unknown 7 metre envelope into a distance you can build a setup around.
- Decide whether any pick, boom position or scaffold run has to be inside the limit. If so, book the utility’s involvement as a schedule item with a lead time, not a phone call made on the day.
- Name the signaller in writing for every setup near a line, and give that person nothing else to do.
- Re-check the envelope when anything changes: a new boom length, a repositioned pump, a trailer with a taller load, a temperature swing on a long span. On a multi-employer site, coordinating that across trades is the prime contractor’s job, which we cover in prime contractor requirements in Alberta.
Talk to us before the pump is booked
After 38 years pouring concrete in this city, we have sat through enough pour-morning standoffs to know that the power line problem is created at the drawing stage and discovered at the setup. The cheap version of this conversation happens while the pour sequence, the pump type and the access route are still lines on paper.
Reach our commercial concrete contractors in Calgary to walk the access and equipment envelope before mobilisation, or see our foundations work in Calgary for the cage and form picks that drive most of the reaching on a foundation job.
FAQ
What is the safe distance from an overhead power line in Alberta? It depends on operating voltage, which has to come from the line’s owner. Until it is confirmed, 7 metres applies. Once confirmed, Schedule 4 governs: 3.0 metres for 750 V to 40 kV, rising to 7.0 metres at 500 kV.
Who do we have to contact before working near a line? The line’s owner — Part 17 describes it as an electric utility, a rural electrification association, or an industrial power producer. The call establishes voltage; if work has to be closer than the governing distance, the owner must also be notified before work begins and must provide assistance.
Does the rule apply if the line looks dead? Yes. Since the 2023 amendment, Part 17 no longer uses the word “energized” — every overhead line is treated as energized, so appearance is not a basis for reducing clearance.
Is the pump supplier responsible for clearance, or are we? The duty sits with the employer and, since 2023, with the worker as well. A pump arriving on your site does not move the obligation to the supplier, and on a multi-employer project the prime contractor still owns coordination between trades.
Sources
- Government of Alberta, OHS Code Part 17 Overhead Power Lines — Explanation Guide
- Government of Alberta, Change highlights — Parts 17 and 40, OHS Code, effective 31 March 2023
- Utility Safety Partners, High-risk activities — Look Up and Live
- University of Calgary, Overhead Power Lines Program