Clearing medium-voltage lines

To prevent vegetation from growing too close to medium-voltage lines, Hydro-Québec uses control methods that respect the natural environment and promote biodiversity (preserve as many animal and plant species as possible) while remaining cost-effective.

Depending on the situation or location, different types of work are done.

Pruning

Pruning involves cutting tree branches to ensure a safe clearance around medium-voltage lines. Pruning is done mainly in developed areas (cities, suburbs and villages). This method causes the least disturbance to vegetation, thereby helping preserve natural habitats and protect biodiversity. However, pruning is a difficult, dangerous and costly operation that must be repeated regularly (every three to six years).

Every year, Hydro-Québec prunes trees along nearly 150,000 spans (a span is a section of an overhead line between two neighboring poles). This is an enormous, never-ending task that we can all make easier by choosing trees that won’t grow too close to medium-voltage lines.

The right tree in the right place

If you’re planning to plant a tree near a distribution line, there’s an easy way to avoid problems.

You can avoid any unpleasant surprises by using our handy Choose the Right Tree or Shrub tool.

Tree-pruning procedure

A tree trimmer hired by Hydro-Québec prunes and picks up tree branches.

For non-ornamental trees, such as roadside woods, the clearing width is greater and the residue may be left spread over the ground or in small piles (windrows) to encourage biodiversity.

There’s no cost to the owner of the tree.

Clearing

This approach is reserved for forested areas. Clearing involves cutting all wide-spreading trees down to ground level while maintaining low-growing vegetation that will not come too close to medium-voltage lines. This vegetation control method preserves a diversified plant cover that provides habitat for various animal species.

Every year, Hydro-Québec clears over 20,000 spans (a span is a section of an overhead line between two neighboring poles).

Clearing is carried out every 6 to 12 years.

Strip of land underneath a power line where selective clearing has been done. Small mounds of wood, or windrows, are visible at the edge of the cleared area.

Land-clearing procedure

A qualified cutter hired by Hydro-Québec cuts down the trees and may or may not pick up the residue. Residue can be chipped (and picked up or not), left spread over the ground or put in small piles (windrows) to encourage biodiversity. There’s no cost to the owner of the tree.

Wood and branches left on the ground

Residual wood and branches have a role to play in preserving biodiversity. This residue, chipped or left as is, can be scattered over the ground. As it decomposes, it provides some of the organic matter that is so necessary for Québec soil, given our short decomposition seasons and cold temperatures.

When piled into small mounds called windrows, the residue provides long-term habitat for wildlife and invertebrates.

Finally, dead wood from large-diameter trees promotes the germination of certain plant species and plays a role in water retention and erosion control.

When trees that are compatible with the power system are preserved and branches are left on site in windrows, the right-of-way becomes an attractive habitat for the white-throated sparrow (Zonotrichia albicollis). It can find food and shelter in the right-of-way and even nest there.
Preserving a small fir snag after clearing the land underneath a distribution line.

Snag preservation

Snags are the trunks of dead or dying trees that are still standing. They play a key role in our ecosystems since dead wood is a boon for mushrooms and insects. Over time, these organisms create cavities where small mammals take shelter to give birth or protect themselves from predators. Snags are home to a wide variety of species of mushrooms, plants, invertebrates, birds and small mammals. Hydro-Québec therefore recommends keeping them, as long as stringent safety criteria are met.

Cutting down weakened trees

Trees that show signs of structural weakness (partially uprooted trees, trees damaged in a storm, etc.) and are in danger of falling on distribution lines are cut down.

The first step in planning this operation is identifying hazard trees. This complex task is carried out only by arborists.

Procedure for felling weakened trees

An arborist hired by Hydro-Québec cuts down the trees and may or may not pick up the residue. Residue can be chipped (and picked up or not), left spread over the ground or put in small piles (windrows). Commercial timber is not chipped, but left as is for firewood and various other uses. There’s no cost to the owner of the tree.

A Hydro-Québec forestry engineer assesses the mechanical strength of an arborvitae (white cedar) that has a lengthwise slit and indications of wood decay near the trunk.

Pruning or felling to restore power

Following a major weather event (wind, snow or freezing rain) or an accident that has resulted in outages, Hydro-Québec prunes or cuts down trees as required to restore power safely and prevent further outages.

Procedure for felling or pruning tree to restore power

Hydro-Québec or an arborist hired by the company carries out the required work, at no charge to the tree’s owner, but does not pick up the residue. That responsibility falls to the municipality or owner.