Aug 29, 2016
Play it safe around power lines
By Linda Johnson
In July 1999, Curtis Weber was 17 and working on a construction site in Saskatchewan. He and two co-workers were putting a steel grain bin on top of a hopper bottom. They had identified an overhead power line, and as they approached the overhead line, it was Weber’s job to steady the bin against high winds. But the crane operator failed to lower the boom far enough and backed into the power line.
Weber was hit by 14,400 volts of electricity, which went through his body three times. He suffered
third- and fourth-degree burns to more than 60 per cent of his body, including his face. His right arm and left leg were amputated.
Power lines are often present on construction sites and pose a serious hazard to workers. Because electricity naturally seeks the ground, a piece of equipment or machinery that touches or goes near a line can send high-voltage electricity (more than 750 volts) travelling downwards through the equipment. Within seconds, the surrounding ground and other equipment may also become energized.
The main danger of power lines is, of course, electrocution, which may cause severe internal and external burns and often death. Sometimes, a foot or hand has to be amputated. The electric current can also stop the heart.
“They may look pretty safe: a line up above, nothing sparking. But touch it or come close to it and the energy that’s travelling in that line will want to jump over and come to ground. It will travel down the easiest path it has,” says Scott Saint, chief public safety officer at the Electrical Safety Authority in Mississauga, Ont. “Power lines are very lethal. They can kill in an instant, before you even recognize there’s a danger.”
In Ontario, overhead power-line contact has killed 24 people in the past 10 years. Moreover, construction workers are at an especially high risk: 70 per cent of power-line contacts in the past 10 years have occurred on construction sites.
Power-line contacts most commonly affect construction workers operating excavating equipment, for example, backhoes and larger excavators, says John Curran, manager of safety and environment at Newfoundland Power in St. John’s, N.L. Other examples of heavy equipment that can contact power lines are cranes, boom trucks and garbage dumpster trucks.
An increasing number of incidents also involve dump trucks, Saint says.
“We’re seeing a much higher incident level of contact by dump trucks on power lines. That’s a danger to the dump truck operator and it’s a danger to the people around there because, in an extreme case, the truck can pull the line right down,” he says.
Many construction companies are recognizing the need to get the message out that dump truck drivers need to be more aware of their boxes and remember to lower them, Saint says. More companies are also requiring that trucks have buzzers built into the truck cab. As the box starts to rise, it triggers a buzzer to sound, and the noise stays on until the dump box is lowered.
“It’s a simple measure, but it can be very effective because it’s a reminder: you have the buzzing going on, you know you have to lower the box,” he says. “It’s a busy construction site. People are moving quickly and, sometimes, people forget that their box is raised and they have contact with the power line.”
Construction workers working with tools or materials capable of making contact with electrical equipment are also at risk, he says. Tools such as ladders and scaffolds are good conductors of electricity.
“If contact is made in these instances, the path to ground will undoubtedly be through the worker and severe injury is imminent. These types of contacts with energized power lines are more likely to result in death,” says Curran.
Power lines can be just as dangerous even when there is no direct contact. Workers themselves and the metal equipment they work around can attract electricity, causing the electricity to jump, or “arc,” from the lines to a conducting object, such as a metal ladder, truck or person. The chances of arcing increase with the voltage.
Moreover, while most concern is around high-voltage lines, it’s important to remember that power lines carrying fewer than 750 volts can kill.
While going through the vehicle to get to the ground, electricity will often go around the operator in the cab, says Curran.
“Of course, this is not always the case, and workers must remain vigilant at all times when working around electrical equipment,” he says. “Any worker standing near a piece of equipment when contact is made is also at great risk. If an individual is touching the exterior of energized equipment at the time of the contact, then injury is imminent. If an individual is standing nearby and the electricity enters the ground, injury is also is quite likely.”
When equipment contacts a power line or a line falls to the ground, an electrical current may flow into the ground creating a “pool” of electricity in the surrounding ground. The voltage is highest close to the equipment; farther away, it gradually drops off. The electrified ground will energize anything that touches it. This poses a particular risk to the equipment operator, Saint says.
“It’s a scary situation, when the tires on your truck are smoking because of your contact with the power lines. The normal driver wants to jump out, but that can be very dangerous,” he says. “If you get out of the truck, you can be injured or killed because the electricity is travelling through the ground. If you take a step, the electricity can travel up from the ground through one leg and then down the other leg, passing through your heart as it does it.”
Thus, if equipment touches a line, he says, workers should know to stay inside their vehicle.
“Stay in your truck. The rubber tires, although they may smoke, will still insulate you from the danger. Ask someone to call 911 and have the utility also come out and disconnect the line,” Saint says.
If an operator or driver must leave the vehicle — in the event of a fire or other hazard — they need to get out without touching the vehicle and ground at the same time. The worker should jump about 45 to 60 centimetres away from the energized vehicle, landing with feet together and hands by the sides. Keeping the feet touching, the workers must then shuffle away, never allowing the heel of one foot to pass the toes of the other. Alternatively, hop with both feet together until at least 10 metres away.
Other workers can avoid the potential of energized ground by staying at least 10 metres away from operating machinery — if a boom is moving, for example. Wait until the machinery is not operating before approaching it.
The large rubber tires on trucks and heavy equipment constitute a further risk because contact with high-voltage power lines can cause tires to explode. Extreme heat causes hydrocarbon vapours to be released inside the tire, which in turn causes the air pressure and temperature to rise drastically. If the vapour, which is highly flammable, comes in contact with very hot oxygen, it will ignite and the tire will explode.
Workers can be injured or killed by flying tire or wheel parts, so anyone in the area who sees a vehicle smoking should not approach it.
Safe work procedures
Dwight Larkin, health and safety co-ordinator at Fermar Paving, a road construction and paving company based in Rexdale, Ont., says his workers do a lot of work near both overhead and underground wires.
When a job site opens and before any work starts, he says, supervisors check to see where overhead wires are and obtain underground “locates.” They then put up signs warning of overhead wires. These signs are located near the power lines and serve as a constant reminder to workers.
Warning signs should be specific (stating the hazard and voltage) and located so at least one is always visible to operators working in the area. They should also be legible in all conditions, such as rain and night, during which work is done.
Then, Larkin adds, every day, before work starts, supervisors and workers do a site assessment, discuss all job-site hazards and review the measures they can take to prevent incidents. During the site assessment, workers should be looking around, both at the ground and up in the air.
It’s also important to identify where people will be working near power lines and assign others to be spotters, or signallers: workers who stand and watch and can warn a driver when equipment is getting too close to power lines.
Supervisors also do weekly site inspections and tailgate meetings, as well as additional tailgates as needed Larkin says.
“If we have a near miss on one job site, then we try to discuss that near miss at all the other job sites, so if they come across a similar situation, the workers understand what they should be doing.”
To ensure workers are following proper procedures, Larkin and another safety manager visit job sites every couple of weeks.
“And if we see something we don’t like, then we’ll stop and explain why they have to do what they have to do.”
Generally, the employer is responsible for determining the voltage of power lines on a work site and for informing workers of the location and voltage of high-voltage lines. Material and equipment should not be stored under power lines. Workers and supervisors should look for overhead lines before moving ladders, rolling scaffolds or elevating work platforms.
Melody Mateev, HSE co-ordinator at Edmonton-based ATCO Electric, a utility with 80,000 customers across Alberta, says companies that need
to work near power lines should
contact their utility before starting a job so the utility can measure the voltage. Companies should also make a work plan and know the height of their equipment.
It’s important for workers to know and maintain the regulated safe distances, or “limits of approach,” the minimum distances between power lines and people, machinery or tools required to prevent direct contact and arcing, Mateev says. In Alberta, workers must keep 7 metres away from power lines, she adds.
In Nova Scotia, the limit of approach is 6 metres. In New Brunswick, that limit is 3.6 metres. In other jurisdictions, such as Ontario, Quebec and B.C., regulations put the minimum safe distance at 3 metres (although B.C. Hydro advises 20 metres). These distances vary depending on the voltage. In Ontario, for example, the distances are:
• 750 to 150,000 volts — 3 metres
• 150,001 to 250,000 volts — 4.5 metres
• 250,001+ volts — 6 metres.
In Newfoundland and Labrador, Curran says, anyone working around power lines must maintain 5.5 metres from energized, high-voltage power lines.
“There is also a legal obligation for workers who operate equipment capable of contacting power lines to complete a provincially prescribed power-line hazard training course. In some cases, permission can be given by the electrical utility to go within three metres,” he says.
At the time of his accident, Weber was not expected to survive. However, after six years of surgeries and physiotherapy, he was able to go on with his life. Now a safety officer with the Saskatchewan Health Region, he spends much of his time doing presentations, encouraging workers to speak up when they have concerns about a job and promoting safe practices, particularly around power lines.
Linda Johnson is a freelance journalist based in Toronto. She can be reached at
This article originally appeared in the
issue of COS.