How Hydro-Québec clears vegetation near power lines and manages the debris

To keep vegetation from growing too close to medium-voltage power lines, Hydro-Québec uses environmentally friendly control methods like pruning, clearing and, in the case of weakened trees, felling. It also deals with the resulting debris efficiently, responsibly and fairly.

In a distribution system spanning over 100,000 km, vegetation control must be applied to roughly 17,000 km of power lines per year. It’s a tough and lengthy job—one that must be carried out branch by branch and tree by tree.

How can you make this job easier?

When planting trees on your property, you can help reduce the need for future vegetation control by choosing species that, as they grow, won’t encroah on medium-voltage power lines.

Use our handy Choose the Right Tree or Shrub tool to identify species that will remain within a safe distance of power lines as they mature.

Debris removal: Which situation applies to you?

Hydro-Québec had to act quickly and prune my trees/my neighbor’s trees to restore service.

This type of unscheduled maintenance qualifies as an emergency intervention. There’s no cost to the owner of the tree, but the resulting debris will be left where it is.

I’ve shared my safety concerns with Hydro-Québec, who assessed the risk to the power grid and agreed to take action.

This qualifies as unscheduled maintenance. There’s no cost to the owner of the tree, but the resulting debris will be left where it is.

Hydro-Québec has performed regular scheduled vegetation control on my trees/my neighbor’s trees.

If the trees are ornamental, the debris will be chipped and collected, with a few exceptions.
Merchantable trees will be trimmed minimally and laid out at the forest’s edge.
In all other cases, the resulting debris will be left where it is

Hydro-Québec has asked for my permission to fell a tree on my property that represents a high risk to the power grid. I’ve agreed to have it cut down.

If the tree in question is ornamental, the debris will be collected.
Merchantable trees will be trimmed minimally and laid out at the forest’s edge.
In all other cases, the resulting debris will be left where it is.

Hydro-Québec or the company it has hired has clear-cut just about all the trees lining the roadway on both sides of the power line.

Tree debris between the roadway and power line will be either collected or chipped on-site, while debris between power line and forest will be left where it is, either spread over the ground or piled in small mounds known as windrows.

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


Pruning involves cutting tree branches to ensure safe clearance around medium-voltage lines. Carried out mainly in developed environments (cities, suburbs, villages), pruning constitutes the bulk of Hydro-Québec’s vegetation control. The fact that it is minimally disruptive helps to preserve habitats and maintain biodiversity—for example, in urban or suburban woodlands and green areas. Nonetheless, pruning is a difficult, dangerous and costly operation that must be carefully planned. The interactive map When will we be in your area? shows you when work has been planned for where you live.

Strip of land beneath a power line where selective clearing has been carried out. Small mounds of wood, or windrows, can be seen at the edge of the cleared area.


This approach is reserved for forested areas. Clearing is a process that involves cutting taller trees down to ground level while maintaining low-growing vegetation that will not encroach on medium-voltage lines. This preserves a diversified plant cover that provides habitat for various animal species.

Each year, Hydro-Québec clears over 20,000 spans (a “span” is a section of an overhead line between two neighboring poles). The owner’s permission is required before the clearing can take place. Should the owner refuse, Hydro-Québec will prune the trees instead.

Clearing is carried out every six to twelve years.

Felling 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 (felled).

Whenever a tree poses a high risk to the power system, Hydro-Québec will ask the owner for permission to cut it down. Owners who refuse should know that some Hydro-Québec customers may suffer damages as a result of outages caused by the tree or its branches falling onto the power lines. Dispatching a line crew to restore electricity service typically costs thousands of dollars . . . and Hydro-Québec could claim the costs from the owner. That’s why we advise owners to check with their insurer and see if they’re covered for civil liability in such cases.

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

How is the debris managed?

How debris (tree trimmings, branches, foliage) is managed will differ depending on whether the operation was unscheduled—i.e., due to an outage, weather event, accident, potential hazard, etc.—or just part of routine vegetation control.

For unscheduled operations

Following major weather events like wind, snow or freezing rain, as well as any other sort of incident resulting in an outage, Hydro-Québec will prune or cut down trees as needed to restore power promptly and safely and prevent further outages.

Hydro-Québec or an arborist hired by the company will carry out the work at no charge to the tree’s owner; however, the owner is responsible for disposing of the resulting debris.

Tree owners can dispose of the debris in a number of ways: by using it as fuel, hauling it to an eco-center or preparing it for collection by the municipality, as per the regulations in effect.

For scheduled operations

When vegetation control (pruning, clearing or felling) has been planned by Hydro-Québec as part of power grid maintenance operations and/or to mitigate the risk or frequency of outages, then how the debris is handled will differ based on whether the tree is merchantable, ornamental or another variety.

Merchantable wood

On municipal or provincial land, wood that has commercial value (merchantable wood) is treated in line with an agreement made with the municipality or the Ministère de l’Énergie et des Ressources naturelles du Québec. Otherwise, it is trimmed minimally and piled along the forest’s edge, so the property owner can recover it more easily.

Ornamental trees

A tree is considered ornamental if it is part of a landscaping design or is grown for other aesthetic or functional reasons (e.g., windbreaks, visual or sound barriers).

Its debris is chipped and collected at no cost to the owner by Hydro-Québec or an arborist hired by Hydro-Québec, then disposed of at a recognized recovery center.

All other trees

For non-ornamental and non-merchantable species such as roadside trees, the clearing width is greater. Trimmings are left where they are, either spread over the ground or piled in small mounds known as windrows.

This work is carried out by a company hired by Hydro-Québec at no cost to tree owners. The rules that apply to processing these trees are the same for all customers.

In applying these measures, Hydro-Québec achieves substantial savings, since recovering and disposing of tree trimmings can account for nearly half the total cost of clearing the power lines and safeguarding the network. Hydro-Québec also makes a sustained effort to protect plants and wildlife in the immediate vicinity of its equipment.

Traitement des résidus : quelle situation s’applique au cas qui vous intéresse ?

Where is the debris left when the operation takes place alongside the roads?

Alongside the roads, for reasons to do with both safety and aesthetics, the debris resulting from vegetation control is always placed between the power line and the forest’s edge, never between the road and the line. In these environments, the debris might also be chipped; the chips are then blown into the strip of land that has been cleared beneath the line.

Why are wood and branches left on the ground?

Tree trimmings have a role to play in preserving biodiversity. Chipped or left as is, wood debris can be scattered over the ground. As it decomposes, it provides some of the organic matter that is so vital to Québec soil, given our short decomposition season.

When piled into small mounds (windrows), the debris provides long-term habitat for wildlife and invertebrates.

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

When trees compatible with the power system are preserved and the trimmings are left on-site piled into windrows,
the right-of-way becomes an attractive habitat for the white-throated sparrow (Zonotrichia albicollis).
T hese birds can find food and shelter in the right-of-way and even nest there.

Why should snags be left in place?

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 mushrooms, plants, invertebrates, birds and small mammals. Hydro-Québec therefore recommends keeping them so long as stringent safety criteria are met.

Preserving a small fir snag after clearing the land beneath a distribution line.