The hydrovac signalled, slowed, and pulled to the side of the highway. The operator and his swamper had just pulled up to the job site: they would be digging holes for two new utility poles that would soon be mounted with brand new power lines, replacing the existing ones.
The two crew members began setting up to dig like they did every morning. The swamper boomed out using the side controls, carefully lifted the boom off the side tray, and then began reeling out the hose from the water cabinet. The operator, remote control hanging around his neck, was pulling the dig tube down from the driver’s side mount where it was secured.
Then tragedy struck.
As the operator pulled the dig tube down, the remote buttons somehow had pressure applied to it, and the boom began swinging away from the truck, and into the existing overhead power lines.
27,600 volts of electricity ran down the boom, into the truck, and through the swamper, electrocuting him.
Earlier that year, a hydrovac operator was daylighting an underground power cable when his spinner hit a splice, damaging the line and sending an 8000-volt shock through his body.
He was sent to a hospital but survived.
As a hydrovac company, working near high voltage power lines is part of the everyday job. The two biggest hazards are the boom coming into contact with overhead lines and damaging buried lines that are being excavated.
But another major danger is complacency: not being mindful of where the boom is, not using a spotter, carelessness with the remote, and forgetting to put away the boom before moving the truck can all contribute to incidents with power lines.
How can hydrovac professionals minimize the risks?
Steps to take when excavating underground power lines
Before any hydrovac excavation takes place, make sure you have a pre-dig meeting and hazard assessment with every worker present. This is where you will identify what kinds of utilities you’ll be daylighting and what precautions you’ll be taking to minimize the risks.
One of the easiest ways to ensure a safe excavation with power lines is lowering the water pressure. Turning down the pressure you’re digging with significantly reduces the chances of damaging the line, especially when you get close to the depth you’re expecting the line to be.
Next, make sure you’re using an oscillating single jet spinner and not a straight jet. Avoid jabbing motions with the dig wand, as well as digging in a motion parallel to the cable. Instead, dig in a constant circular motion to prevent damaging the line. Using urethane-ended dig tubes helps prevent damage to the line from your dig tube accidentally hitting it.
Dig down beside where the locator has marked the power line, then towards the utility once depth has been reached. Once the buried power cable has been exposed, keep a good 7 inches between the dig wand spinner and the exposed cable.
Usually, the utility company will require one of their representatives to be present on lines over a certain voltage. This is anything within 5 m of a 72 kV line.
When hydro excavating primary lines, it may be required to use an equipotential bonding mat. With Fortis, only pre-registered professionals can excavate using equipotential bonding mats. They will need to be present and will give everyone present a short orientation and pre-dig meeting to go over the possible dangers.
Finally, if a splice is located, contact the utility company that owns it and let them know.
Steps to take when working near overhead power lines
When working near overhead power lines, obviously the biggest danger is the boom coming too close to energized cables.
It’s important to know what kind of lines you’re dealing with. The first step is to call the utility company to find out the voltages of all power lines in the project area.
When operating machinery or equipment in close proximity to power lines, always maintain the limits of approach: from three to seven metres or 10-23 feet depending on the voltage. If the voltage is unknown, keep 7 m away.
Have a spotter watching the boom. Ideally, this is a third person on site that is supervising the hydrovac crew while they set up, excavate, and pack up.
The primary lines are typically located at the top of the pole and do not run to the home or business. These lines are high voltage, and the minimum distance to stay away while working is 7 m.
Secondary overhead lines are the wires that run from pole to pole, and are typically located directly below the primary lines in the middle of the pole. These lines carry a lower, but still dangerous voltage. The minimum distance varies depending on the voltage and is usually between 3-5 m.
Service lines run from the main power pole to the home or business. These lines carry lower voltage. The minimum distance is 1 m.
The communication cable lines are lower voltage but obviously, contact should still be avoided.
One of the biggest dangers is forgetting to lower and put away your boom before moving the truck. Double check. Walk around your truck before you get in.
Keeping your head in the game is key. Be aware of where your boom is at all times. Don’t let complacency set in. Use a spotter.
Being aware of job hazards before you start, using a spotter, communicating, lowering your pressure, and keeping your distance will minimize your risks when working with power lines.
Epcor Handbook for Contractors: GUIDELINES FOR WORKING IN CLOSE PROXIMITY TO ELECTRICAL EQUIPMENT