Project Details

As we work to build new long-term sources of renewable electricity, we’re committed to making the most of the renewable sources we have now.

Proposed change

We have decided to put the project on hold and include components of it as part of discussions with the First Nation of Na-Cho Nyäk Dun about relicensing the Mayo Generation Station.

The Mayo Lake Enhanced Storage Project would help us generate more renewable electricity in the late winter and spring on average, by using more of the water available in Mayo Lake.

This does not mean raising lake levels. Instead, we would amend our existing water use licence to allow us to use an additional one metre of water that is already available on the lake. This is called bottom storage.

This would happen in two phases.

  • Phase 1: In the first few years, we would lower the current low supply level on the lake by up to 0.5 metres.
  • Phase 2: After several years of monitoring, we, together with the First Nation of Na-Cho Nyäk Dun, would determine if the low supply level could be lowered again by another 0.5 metres, if it should stay the same, or be raised back to the previous licence limit. This would be determined according to the results of our ongoing annual monitoring program and the environmental thresholds in our adaptive management plan.

Project benefits

  • Generates more renewable electricity
  • Reduces greenhouse gas emissions
  • Saves Yukoners money by avoiding the use of some fossil fuels. Hydro power is cheaper than current diesel and LNG prices
  • PHASE 1: Old cofferdam remnants will be removed
  • PHASE 2: If needed, narrow dredging of the main outlet channel would occur

Mayo Lake outlet channel sediment

In the nearly 70 years since the Mayo Lake control structure was built, the outlet channel has accumulated a considerable amount of sediment. Some of this sediment needs to be removed so water can move more efficiently from Mayo Lake. This is true whether or not we proceed with this project. Improvements to the outlet channel will also make it easier to access Mayo Lake by boat across a wider range of water levels.

Maintenance activities are planned over two phases. During each phase of the maintenance activities, a number of mitigation measures will be used to reduce any adverse effects to fish, wildlife or their habitats.


Removing the cofferdam remnants near the existing boat launch. This will likely be done with a long reach excavator. This may cause the portion of the outlet channel closer to Mayo Lake to naturally create a deeper channel. This will be monitored to determine if this occurs.


Dredging in the main outlet channel to remove sediment in order to restore a deeper channel. Multiple options for how the dredging will be done and where the sediment will be moved to will be assessed.