Hydro One has completed an Environmental Study Report (ESR) to expand the existing Marathon Transformer Station (TS) in the Town of Marathon. 

This undertaking is required to connect the proposed new East-West Tie transmission line to the station. To accommodate this work, the existing Marathon TS would have to be expanded by approximately five hectares onto adjacent Crown land.


A Environmental Study Report (ESR) and the appendices documents consultation on the planning and decision-making process followed during the Class Environmental Assessment. The public review and comment period ended on April 9, 2018. Thank you to those who submitted their feedback.

More information is available in the 
Notice of Completion (aussi disponible en français), which was published on March 6 and March 13 in the Marathon Mercury newspaper.

More information is also available in the
Notice of Commencement (aussi disponible en français), which was published on May 23 in the Marathon Mercury newspaper.

Public Information Centre

Thank you to those who attended our Public Information Centre (PIC) on July 25, 2017 to learn more about the project, environmental studies and considerations, and to discuss the relocation of the Shack Lake access trail.


Project Approval Requirements

The proposed Marathon TS expansion project is subject to the Class EA for Minor Transmission Facilities (Hydro One, 2016), an approved planning process under the Environmental Assessment Act. The Class EA was developed as a streamlined process to ensure that minor transmission projects that have a predictable range of effects are planned and carried out in​​ an environmentally acceptable manner.

The proposed work will also be carried out according to the requirements set out in the Class EA for Resource Stewardship and Facility Development Projects (MNR, 2002).

In addition, Section 92 approval from the Ontario Energy Board (OEB) is required for the proposed new East-West Tie Project and all associated work, including the proposed station expansion at Marathon TS. Click here for more information about our application to the OEB (please look under EB-2017-0194).

  • March 2017

  • Notification sent to First Nations,
    Métis communities and Town of Marathon

  • May 2017

  • Notice of Commencement issued for the Class Environmental Assessment

  • July 2017

  • Public Information Centre

  • March 9 - April 9, 2018

  • 30-day public review and comment period for the draft Environmental Study Report (ESR)

  • November 2018

  • Final ESR filed with the Ministry of Environment, Conservation and Parks (MECP)

  • January 2019

  • Anticipated Section 92 decision by the Ontario Energy Board (OEB)

  • Q2 2019

  • Anticipated start of construction (contingent on the outcome of the OEB approval)

  • Q2 2021

  • Anticipated project in-service

Marathon TS is located at 217 Peninsula Road, Marathon.
Click the button below to view the project map.

Click to enlarge map

For more project information, please contact:

Stephanie Hodsoll
Community Relations
Hydro One Networks Inc.

Tel: 1-877-345-6799
Fax: 416-345-6984