What is the Class Environmental Assessment process?
The planning of this proposed project will follow the Class Environmental Assessment for Minor Transmission Facilities (2022) in accordance with the Ontario Environmental Assessment Act.
An environmental assessment (EA) is a regulated decision-making tool and a key step for the planning and building of transmission infrastructure in Ontario. The EA ensures that potential natural, economic, social and cultural effects are thoroughly considered before a project begins.
A Class EA includes assessing the project study area, identifying and evaluating alternatives associated with the project, consultation with stakeholders and rights-holders, identifying potential effects, mitigation measures and approvals, and documenting the process, studies, decisions and commitments into an Environmental Study Report.
What EA activities have taken place to date?
Over the past year, the project team explored possible routes, identified constraints and opportunities, and developed a technically feasible alignment based on feedback from key stakeholders like the Ministry of Transportation and Infrastructure Ontario.
Several desktop and field studies were conducted in 2024, such as:
- A desktop archaeology assessment to identify archaeological potential
- Ecological land classification to determine vegetation communities and potential habitat types
- Aquatic habitat assessments
- Significant wildlife habitat assessment
- Species at risk habitat assessment
- Geotechnical studies to confirm local conditions and engineering construction requirements.
Archaeological field assessments will be planned to occur in Spring 2025, based on the findings of the desktop study.
Why is this the only route you’re exploring?
Hydro One explored several route alternatives. Since November 2023, we’ve gathered environmental and technical data, along with feedback on the study area. Our team considered technical, socio-economic, and environmental factors, and looked for ways to use existing transmission corridors, road allowances, and additional open areas to reduce impacts to the community.
The proposed preferred route was selected as the only viable option due to several constraints in the area, including:
- Ministry of Transportation (MTO) setbacks for towers and junction stations
- Reserved land for a future transitway
- Hwy 404/407 ramps
- Infrastructure Ontario (IO) lease with an existing business
- Existing utilities
- Private property north of Hwy 407
A map of the constraints in the area is included in the display panels from Community Open House #1.
Why are you proposing to build a new transmission line in this corridor and not somewhere else?
As the trusted builder and operator of transmission lines in Ontario, Hydro One has a regulatory duty to connect customers to Ontario’s electricity grid.
Hydro One has an easement on the provincially-owned lands within the existing hydro corridor (the Parkway Belt) where we’re proposing to build a new overhead transmission line. The proposed route and junction location is the only viable option given the constraints in the area.
This hydro corridor has been reserved since 1978 for an overhead transmission line to support the power grid in the Greater Toronto Area. When the hydro corridor was first established, it was planned to accommodate four transmission lines. The overhead portion of this new proposed line is being designed with future expansion needs in mind.
Why is there an underground transmission cable and an overhead transmission line? Why can’t the entire project be underground?
There are several constraints north of the existing hydro corridor that prevent us from building an overhead line directly to the new Commerce TS. As a result, an underground cable through Leslie Street and Commerce Valley Drive is the only viable solution to connect the new transformer station to the grid.
There are several factors to consider when it comes to burying high-voltage transmission wires, such as the technical feasibility, potential disruption to the surface, and the costs involved.
Burying transmission lines can be highly disruptive to the environment given the magnitude of construction work that would be required. It comes at significantly higher costs and presents maintenance challenges as it takes significantly more time than overhead equipment to repair in case of an emergency and has a shorter lifespan.
The majority of Hydro One’s 30,000 km of high voltage transmission infrastructure is built above-ground. There are minor exceptions like when there isn’t sufficient space to build an overhead wire.
What will the towers look like? How tall will they be? How many will there be and where are they located?
The overhead line will be built using lattice towers and monopoles and be similar height to the existing northern 230 kV circuit. (Approx. 46 m tall), located along the north side of the existing hydro corridor.
They will be located in-line with the existing towers from the existing transmission lines, except near the junction locations where there are additional structures required. Once the overall design is further progressed, we’ll have more information about the tower types and exact locations.
Why are the proposed junction stations needed?
For the Commerce TS and Line project, the proposed junction stations are required where the 230 kV overhead transmission lines are transitioned from overhead lines to underground cables.
The tallest component within the junction station is a structure that we call a “Low Gatineau Tower” and it is approximately 13.5 metres tall.
Hydro One is exploring enhanced screening options including a cedar wood fence. Submit your feedback on screening options at community.relations@hydroone.com or 1.877.345.6799.
Why can’t you build the junction stations under the existing transmission lines, further away from residences?
Constructing the junction stations under the existing lines is not feasible due to reliability, operational, and maintenance constraints.
What is the timeline for this project?
We remain committed to working with community members throughout the project lifecycle. Once the Class EA and project planning are complete, construction could begin as early as spring 2026 to meet the in-service date of 2028.
- The draft environmental study report will be available to the public in spring 2025 for a 30-day review period, with the environmental assessment process concluding in summer 2025.
- Construction on the proposed transformer station, overhead transmission line and underground transmission cable is anticipated to take approximately two years (2026 to 2028).
We will continue to keep the community updated throughout the project. We’ll have more information on construction activities, methods, and staging closer to the end of this year.
Are the proposed transmission line and junction stations safe?
We understand residents who live near our infrastructure may also have questions about safety and electric and magnetic fields (EMF). Although we can’t see electric and magnetic fields, they can be found everywhere electricity is used, including at home from appliances to computers, to offices and electrical stations.
We take safety very seriously and we design and operate our equipment in accordance with all regulatory requirements. Hydro One has a dedicated team that regularly monitors global studies around EMF to ensure that our infrastructure is built and maintained following best practices and industry standards.
Based on global studies which have and continue to be regularly monitored, Health Canada and the World Health Organization do not consider any precautionary measures are needed regarding daily exposures to electric and magnetic fields produced by extremely low frequencies such as transmission lines, including 230 kV lines. Our EMF webpage has more information.
