A space for dialogue

Hydro-Québec wishes to develop this project in collaboration with the communities concerned through a multi-stage public participation process.

This will allow the project team to hear the concerns expressed by the public and by community representatives so that we can adapt the project to the visions of the towns and boroughs where it takes place.

More about the community collaboration process

Contact us

Info-project line
514 385-8888, extension 3462
Monday to Friday from 8:30 a.m. to 5:00 p.m.

Public participation events

Please sign up for our electronic mailing list to receive project updates and details on upcoming information and consultation events.

May 13 2019

Tell us what you think online

Online survey

The project team is gathering feedback in order to better adapt the project to its environment.

Tell us what you think online


3 p.m. to 8 p.m.

Buffet Il Gabbiano

Come meet the project team, find out about the project and ask questions.


3 p.m. to 8 p.m.

Centre de loisirs

Come meet the project team, find out about the project and ask questions.

Open house in Lachine

3 to 8 p.m.

Vieille Brasserie

You’re invited to meet the Hydro-Québec team to learn more about the project and ask questions.

You’re invited to meet the Hydro-Québec team to learn more about the project and ask questions.

More information coming soon

  • Côte-Saint-Luc


Le contenu qui suit est un diaporama d’images sur : Les normes

  • Citizens of Montreal West discuss with the project team at the public information event in October 2019.
  • Two landowners discuss with real estate specialists at the public information event on the Aqueduc-Saraguay project in Montreal-West in October 2019.
  • Citizens of Montreal West consult the project maps and discuss with members of Hydro-Québec’s project team at the public information event in October 2019.
  • A homeowner talks to a real estate specialist during the May 2019 open house on the Aqueduc–Saraguay project in LaSalle.
  • Citizens consult a map and talk to the project manager and the electrical system planner during the May 2019 open house on the Aqueduc–Saraguay project in LaSalle.
  • A citizen asks the environment specialist questions during the May 2019 open house on the Aqueduc–Saraguay project in LaSalle.
  • Citizens learn about the project from two members of the Hydro-Québec team during the May 2019 open house on the Aqueduc–Saraguay project in LaSalle.
  • Citizens learn about the green link project from LaSalle borough employees, who were available to meet with citizens during the May 2019 open house on the Aqueduc–Saraguay project in LaSalle.


What is the electricity transmission system for?

Production : centrales hydroélectriques pour 99,9 %. Transport : lignes et postes. Distribution : lignes pour alimenter les clients.


99% of our electricity is produced by hydropower generating stations, most of which are located in northern Québec.


Hydro-Québec’s transmission system is made up of lines and substations. It supplies electricity to Québec’s residents, most of whom live in the southern part of the province.

To cover these large distances while keeping losses to a minimum, the electrical voltage is increased using transformers in step-up substations. The electricity then travels to other substations over transmission lines (steel wires on towers). Once the electricity arrives near load centres, its voltage is reduced so that it can supply the distribution system.


Finally, the electricity travels through the distribution system over wires attached to wood poles. It arrives at residences and businesses at the correct voltage to power common devices like televisions.

Why is Hydro-Québec planning to upgrade the grid between Aqueduc and Saraguay substations?

  • With the project, Hydro-Québec is addressing the demand for power today and tomorrow. The equipment is aging and must be replaced. As a result of demographic growth and economic development in the area, much more electricity is being used now than ever before.
  • The project will facilitate development and add some 500 MW of capacity to supply a range of economic and social projects in the area.
  • The upgrade is taking place against the broader backdrop of the transmission system development plan for the island of Montréal begun in 2009 to boost Hydro-Québec’s transmission capacity by raising the voltage from 120 kV to 315 kV.
  • The project will improve the reliability of the electricity supply and ensure long-term continuity of service for all the region’s residents. If it isn’t carried out, the risk of outages and malfunctions will increase. It will also become difficult to serve new customers and meet demand in this booming area. Hydro-Québec is required to provide electricity to all Québec residents.

What will the project consist of?

  • The project has two main components:
    • Rebuilding the overhead transmission line, between Aqueduc substation in LaSalle and Saraguay substation in Saint-Laurent, a distance of 18 km, to raise it from 120 kV to 315 kV
    • Converting three 120-kV transformer substations—Laurent substation (in Saint-Laurent), Hampstead substation (in Côte Saint-Luc) and Rockfield substation (in Lachine)—to 315 kV
  • The overhead line will be built on the existing right-of-way. In the upcoming stages, the project team could consider variants on the route with a view to mitigating the impacts of the line, while at the same time taking into account technical, economic, environmental and social feasibility criteria.
  • Hydro-Québec is also taking a preliminary look at building a substation in Dorval, along with a supply line connecting it to the rebuilt transmission line.

Why does Hydro-Québec want to build an overhead rather than an underground line?

The planned line will be built on an existing right-of-way where there is already a 120-kV overhead transmission line.

When does Hydro-Québec opt for underground lines?

Whenever it’s impossible to build an overhead line because of insufficient space or an impassable obstacle such as a building.


  • Service life: 85 years
  • Greater transmission capacity
  • Faster recovery from outages


≈$150 million*


  • Service life: 40 years
  • Lower transmission capacity
  • More complicated to maintain and repair


≈$440 million*

* In discounted costs – parametric estimates

An underground line would cost about $ 290 million more than an overhead line, which would have an impact on electricity rates for all Quebecers.

Underground line: An exceptional measure

  • Hydro-Québec’s transmission system, like all other transmission systems in the world, is mainly an overhead one. Out of 34,000 km of lines, only 200 km (0,7%) are underground, and those are mainly in downtown areas.
  • Examples of the percentage of underground power lines with a voltage of 315 kV and higher in some other places
    • 0.1% in Canada
    • 0.4% in the United States
    • 0.4% in Germany
    • 0.8% in Japan
    Source: International Council on Large Electric Systems (CIGRE)
  • Since underground lines are more expensive, they’re used only in places where an overhead line can’t be built, either for lack of space, as in downtown Montréal, or because of an impassable obstacle like a building.

Costs, service life and transmission capacity

  • The costs of an underground line are determined by a set of variables that have to be analyzed for each project.
  • For this project, a 315-kV underground line would cost about $290 million more, nearly three times more than an overhead line. The overhead line is estimated at $150 million, compared to about $440 million for the underground line (total discounted cost in 2018 dollars).
  • Since Hydro-Québec’s investment choices have a direct impact on electricity rates for all its customers, the company has an obligation to choose the lowest-cost option.
  • The service life of an underground line is about 40 years, whereas an overhead line lasts closer to 85 years. Because the grid has to remain live during rebuilding, we’d have to plan to start over again from scratch in another 40 years if we built an underground line. The estimated cost for the underground line doesn’t factor in the cost of rebuilding after 40 years.
  • Last but not least, an overhead line can carry more electricity than an underground line.

Choosing the optimal course of action

  • Hydro-Québec has a duty to submit the best possible project, one that is technically, economically, environmentally and socially sound and that benefits its customers. In other words, Hydro-Québec must submit a project that meets these criteria:
    • Performs well from a technical perspective
    • Can be carried out at the best possible cost
    • Respects the environment
    • Safeguards the public interest and that of its customers
  • The final project balances all these key criteria. In the case at hand, studies show that building a 315-kV overhead line is the best option.

Impacts and repair

  • An overhead line follows a single route. But for reliability reasons, the two circuits of an underground line must be separated, and therefore, ideally, would go under different streets. The two routes would be completely different from that of the existing line.
  • An overhead-underground junction substation might also have to be built for an underground line: for a 315-kV line, that would be quite sizable.
  • Building an underground line would have some major impacts: laying two separate ducts (under the streets alongside the existing right-of-way), in addition to underground chambers 500 to 800 m apart.
  • Undergrounding a transmission line is more complex and takes longer.

Cooperation with the community

  • Aware of the impacts of such a project on the environment, Hydro-Québec is willing to facilitate initiatives involving greening and sustainable transportation along the power line right-of-way. Hydro-Québec wishes to ensure that the project fits in with the urban development vision of its municipal partners and support their initiatives, such as creating a corridor of biodiversity, connectivity and sustainable mobility along the right-of-way. The feasibility of any such initiatives depends on the specific needs and constraints of the surrounding environment.
  • Hydro-Québec and its partners will establish an approach to integrate the project into its environment. This approach may take the form of public information sessions, coordinating committees, working committees or other mechanisms to be determined with municipal entities and community groups.
  • A regional monitoring committee made up of various community partners will also be set up and will observe the project’s advancement. Working committees will be struck for specific areas or facilities as part of the project.
  • The public is welcome to take part in various information and consultation activities over the next few months. For more information, see the timetable of public participation activities.

Do electric and magnetic fields have any health impacts?

  • Although the electric and magnetic fields (EMFs) on the transmission line right-of-way existing are very weak, Hydro-Québec has performed an analysis to determine the difference between the EMFs associated with the existing line and those associated with the planned line. We found that EMFs will remain weak, well below the public health authorities’ recommended exposure limits.
  • Studies indicate that the electric field generated by the planned 315-kV line will be slightly stronger, but still well below the recommended exposure limit of 4.2 kV/m.* That’s because the electric field is determined by the voltage, which will go from 120 kV up to 315 kV. We should point out that the electric fields do not enter homes, as they are blocked by walls.
  • The magnetic field generated by the planned line will be slightly weaker than that the one generated by the existing line. Even at its strongest, the magnetic field will be well below the recommended exposure limit for the public of 200 μT.* This can be explained by two factors: the distance away from the power lines and the current intensity (amperage). The power lines will be higher, and intensity of the magnetic field will weaken with the distance. In the case of this project, the amperage will be lower, and it is amperage (not voltage) that determines the magnetic field.

    *The recommended exposure limits for electric and magnetic fields are those of the International Commission on Non-Ionizing Radiation Protection (ICNIRP), an organization affiliated with the World Health Organization (WHO).

  • Evidence from a number of scientific studies carried out over the past 40 years has not demonstrated harmful effects on health from exposure to electric and magnetic fields at voltage levels normally present in the environment, such as those emitted by high-voltage power lines at the edge of their right-of-way.
  • Health Canada and the Ministère de la Santé et des Services sociaux du Québec take similar positions on this matter.
  • Although the health impacts of EMFs have never been confirmed, Hydro-Québec has made a commitment to be vigilant and prudent with respect to EMFs and their possible health effects.

The literature downloadable using these links will provide additional information:

What impact will the new line have on property values?

  • Power lines, like roads and railways, are an integral part of our modern landscape.
  • Experts have found that a number of factors influence property values, including market conditions, the proximity of schools and parks, access to transport, the neighborhood and the quality of buildings. Many of these factors are subjective and mean different things to different people: what is important to one buyer might not necessarily be to another.
  • These studies tend to show that, in some extreme cases, when a new electricity transmission corridor is created, the presence of a high-voltage line may play a role in determining the value of properties in urban and rural environments, but any impact observed is minor or barely perceptible and tends to diminish with time.
  • Furthermore, the implementation of mitigation measures (such as landscaping) on rights-of-way is a generally well-perceived factor that may help enhance the desirability of the property and therefore its market value.
  • Like other public companies in Canada, Hydro-Québec pays compensation only when it obtains a servitude to run a power line or purchases lots needed for a project. In this case, the property rights were acquired from landowners in the 1950s.

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