Kemano Second Tunnel (T2) Project

Enhancing the long-term reliability of renewable hydropower for aluminium smelter

Rio Tinto | British Columbia, Canada | 2017-2020

7.6 km of newly-excavated tunnel

250,000 m3 volume of rock to be excavated

Remote site accessible only by air or sea

Mountainous terrain with high avalanche risk


  • BC Works' Kitimat aluminium smelter relies on the guaranteed availability of a stable supply of hydroelectric power that the Kemano Powerhouse provides.
  • Located 75 km southeast of Kitimat, British Columbia, Kemano is only accessible by air or sea.
  • The 960 MW Kemano Powerhouse receives water from the Nechako Reservoir through a single 16-km tunnel that is over 60-years-old.
  • Rio Tinto recognized that a second 16-km tunnel was needed to ensure the long-term reliability of renewable power to the smelter in Kitimat.
  • To connect the powerhouse to the reservoir, the new tunnel must be bored through the mountains in a high avalanche risk environment.
  • Project construction will occur between 2018 and 2020—through two winter seasons where temperatures sit around minus -10 degrees Celsius and avalanches are common.


  • Hatch has been selected by Rio Tinto to provide the engineering, project, and construction management (EPCM) services for the project.
  • The project involves excavating a new 7.6 km portion of tunnel and refurbishing an existing 8.4 km portion of the second tunnel to complete the 16 km-long tunnel to the existing penstocks.
  • The second tunnel will allow Rio Tinto to conduct repairs and maintenance on the original tunnel without impacting power supply to Kitimat operations.
  • The 1,300 t tl'ughus tunnel boring machine (TBM) was purpose-built for the specific ground conditions of the project.
  • A mechanical gate will be installed at the existing T2 intake at Tahtsa Lake, which will also have a lower environmental footprint than building a new intake.
  • An avalanche control system (Gazex) will be implemented at critical points on the mountains to mitigate avalanche risk during project construction.


  • Rio Tinto has involved the Haisla First Nation and the Cheslatta Carrier Nation to ensure that indigenous cultures and traditions are respected.
  • The Cheslatta Carrier Nation selected the name for the TBM—tl’ughus—after the legend of the giant monster snake that bored through the mountains, a story that shares many parallels with the T2 project. Students from the Haisla Nation participated in a contest to the design the artwork on the cutterhead of the TBM.
  • Once complete, the upgrade is expected to take the 60-year-old Kemano generating station well beyond 100 years.
  • The environmental team is introducing a number of controls to safeguard protected species in the area, including fish, amphibians, bears, and mountain goats.
  • BC Works' Kitimat smelter produces aluminium with one of the lowest carbon footprints in the world.

Project Numbers

  • CDN$600M project
  • 300-person workforce at peak construction
  • 7.6 km length of newly-excavated portion of second tunnel by TBM
  • 190 m length of the TBM
  • 3 worker camps
  • 8.4 km refurbished portion of 1990s second tunnel
  • 16 km length of completed second tunnel
  • 250,000 m3 volume of rock to be excavated

In a major milestone for Rio Tinto’s Kemano T2 hydropower project, the tunnel boring machine broke through to complete its journey in October 2021. Congratulations to our client and the project team on reaching this exciting day! The tunnel boring machine cut 7.6 kilometers through the rock in remote mountains over 30 months, completing the route for a 16 kilometer tunnel that was started in the early 1990s. The tunnel will be filled up with water in the middle of 2022, with the project expected to be complete in the second half of 2022.

On October 24, 2018, Rio Tinto, together with the Haisla First Nation and the Cheslatta Carrier Nation, and project contractors, unveiled the fully assembled 1,300 t tunnel boring machine, named tl’ughus, a key milestone towards completing the Kemano T2 Project. Read more, here.

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