How Hydro-Québec controls the height of vegetation in transmission line rights-of-way

To make sure that vegetation does not get too close to its transmission lines, Hydro-Québec applies a variety of interventions that are part of its integrated vegetation management program. This program is updated annually.

The program aims to encourage low-growing, relatively sparse vegetation in rights-of-way. For instance, in woodland settings the approach is to maintain shrubs and low-growing plants that are already well established like dogwood, red currant, wild raspberry, viburnum, yew and grasses.

Over time, these shrubs and grasses take up all the space in the right-of-way, making future vegetation control operations easier and creating a nice plant cover for several animal species.

The personnel in charge of the program include experts working in forestry (forestry engineers and technicians) and the environment (biologists and geographers).

The work is carried out by qualified companies, whose workers are trained to meet Hydro-Québec’s safety requirements.

Video: Why vegetation must be kept away from power lines

This video explains why a corridor is cleared beneath transmission lines and what type of work Hydro-Québec does to make sure transmission line rights-of-way are always clear.

Duration : 4 minutes, 18 seconds

Description of the integrated vegetation management program

The program encompasses a series of activities that recur in the same order:

Step 1 of 5

Planning the work

Every year, Hydro-Québec’s experts determine where work is required to bring the vegetation under control. Their plan depends on several factors, the main one being maintaining a safe distance between vegetation and the power lines.

As a result, there is no need to clear every right-of-way every year. The frequency of clearing operations depends on the type of vegetation in the right-of-way and the time it takes for it to grow back close to the power lines.

The more northerly the transmission line, the longer the right-of-way can go without clearing because vegetation grows more slowly in cooler areas. In southern Québec, where vegetation grows faster, clearing operations are more frequent. Consequently, clearing intervals in Hydro-Québec’s rights-of-way vary from 3 to 13 years.

Step 2 of 5

Conducting an inventory of vegetation and sensitive features

Effective planning of vegetation management work requires knowledge of what is in the rights-of-way. To complete this inventory, Hydro-Québec uses several techniques and information sources:

  • Analysis of high-resolution aerial photos using 3D visualization software to locate vegetation, streams, wetlands, etc.
  • Remote aerials surveys using laser technology (LIDAR, light detection and ranging) to measure the precise distances between trees and power lines.
  • Consultation of data provided by federal, provincial and municipal governments on sensitive environmental features, which allows Hydro-Québec to protect sensitive areas like water intakes or the habitats of threatened and vulnerable plant and animal species.

Step 3 of 5

Determining how the work will be carried out

To make it easier to plan upcoming work, every right-of-way is subdivided into sections. Using this approach, Hydro-Québec’s forestry engineers and technicians can determine how best to do their work, section by section, while still protecting the environment.

A number of aspects are taken into account:

  • The height and density of the vegetation
  • The site’s physical characteristics (landforms, accessibility, etc.)
  • Sensitive features (such as streams)
  • Applicable laws and regulations (especially the Pesticides Management Code)
  • Commitments and agreements made with landowners and community organizations

Mechanical clearing

The most commonly used method for clearing rights-of-way is selective mechanical clearing using manual brush cutters.

To prevent stump shoots, workers can apply a diluted herbicide solution to stumps. They can also use brush cutters equipped with grinders to fell the tree and treat the stump in one go.

Use of selective herbicides

All herbicides used by Hydro-Québec to manage vegetation in rights-of-way are selective herbicides, meaning they only affect woody plants. They are approved by Health Canada and applied as prescribed by law. They pose no danger for wildlife or the general public because we take great care to apply them according to industry standards. For example, Hydro-Québec creates buffer zones around waterways, wells and water intakes where no herbicides can be used.

Debris and residual wood

At the planning stage, Hydro-Québec’s experts also determine how debris (branches, leaves, etc.) and residual wood (trunks) will be disposed of.

Most often, the debris is left scattered on the ground, while residual wood is stacked. Wood debris left in rights-of-way promotes biodiversity. It creates rest areas and cover for several animal species and encourages the presence of certain bird species.

Pre-work communications

Before the work starts, Hydro-Québec sends a notice to the relevant landowners.

Whenever herbicides are applied in rights-of-way, Hydro-Québec produces various documents as required by the Pesticides Management Code, a regulation of the Pesticides Act:

  • Notice to the Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques (MDDELCC)
  • Notice to the municipalities and regional county municipalities (RCMs)
  • Notice in a regional media announcing the upcoming work

Step 4 of 5

Carrying out the work

Unless special circumstances make it impossible, vegetation management work starts after the snow melts and continues for as long as weather permits.

Vegetation management contracts are awarded through a tendering process to companies qualified to bid by Hydro-Québec. For example, workers who perform mechanical clearing are required to have forestry management skills such as brush and tree cutting. In addition, under the Pesticides Act and the Environment Quality Act, the application of selective herbicides must always be supervised by workers who hold a Certificate of Authorization for the Use of Pesticides.

Step 5 of 5

Inspecting the quality of the work

All work is checked by a Hydro-Québec representative who makes sure it complies with the specifications. If any problems are identified, the representative notifies the company that performed the work so that it can make the necessary corrections.

A quality control process encourages companies to strive for continuous improvement. Their work is evaluated on a continuous basis during their contract, and they receive yearly evaluations.