The Government of Yukon is providing an update on the replacement of the Wareham Dam spillway near the Village of Mayo, including new information on risk, design, cost and construction timelines. Yukon Energy's project to replace the spillway is of critical importance to public safety in the Yukon.
Recent independent engineering work confirmed the existing spillway has reached the end of its service life and needs to be replaced. A new March 2026 review of that work confirmed the spillway poses unacceptable risks if it is not replaced.
This work reinforces earlier findings from 2023 through to 2025 that identified accelerating deterioration and the potential for serious consequences, including risks to public safety, the environment and the local economy.
On March 11, 2026, the Government of Yukon's Environmental Compliance and Inspections Unit issued a Supplementary Direction requiring additional mitigation measures to address infrastructure risks. This follows an earlier Inspector's Direction issued on November 14, 2025. These directions confirmed the significance and urgency of the required remediation work.
The latest snowpack report for April 2026 indicates near-average snowpack levels in the Stewart River basin, which includes the Mayo Lake hydro reservoir. Average snowpack does not elevate risk but it does not change the underlying infrastructure risk. The Government of Yukon continues to work with Yukon Energy, the Village of Mayo and the First Nation of Na-Cho Nyäk Dun to mitigate the risk of spillway failure and preparations for the spring snow melt.
As one of the Yukon's three hydro facilities, the Mayo Hydro Facility is essential to providing dependable power year-round, generating 15 megawatts of renewable electricity.
Moving from assessment to action
Yukon Energy has taken steps to advance its project to replace the spillway.
- On March 25, 2026, Yukon Energy submitted a Project Proposal to the Yukon Environmental and Socio-economic Assessment Board (YESAB) outlining the selected design and a three-year construction program.
- In-water construction is expected to begin in early to mid-June 2026.
Completing the first phase of construction will significantly reduce flood risk to the Village of Mayo ahead of the 2027 spring freshet.
Selected design and cost update
Yukon Energy anticipates the Wareham spillway replacement project will cost around $180 million (plus or minus 30 per cent).
This updated cost reflects a refined design and may change as the project progresses. Earlier estimates were based on multiple potential replacement options. Yukon Energy selected the open-channel design because it shortens the construction schedule, reduces flood risk after the first construction season, lowers overall construction and dam safety risks and provides greater cost certainty.
More information about the open channel design is available on Yukon Energy's website and in its YESAB Project Proposal.
Yukon Energy anticipates spending approximately $65 million in 2026 on the first year of construction activities. To strengthen oversight and control costs, Yukon Energy has implemented a phased contracting approach and engaged an independent cost estimator.
Broader investment at Mayo Hydro Facility
The spillway project is part of a broader investment of up to $400 million required over the next five years to maintain and modernize critical infrastructure at the Mayo Hydro Facility. This includes:
- Dam safety annual projects;
- Mayo A Hydro rockslide stabilization and remediation;
- Mayo A Hydro surge chamber replacement;
- Wareham Dam spillway replacement;
- Wareham spillway concrete repair;
- Mayo B Hydro Unit overhaul and plant upgrades;
- Mayo A Hydro access road stability;
- Mayo A Hydro plant renewal or replacement;
- Mayo generating station intake improvements;
- Mayo generating station gates and turbine inlet valve certifications;
- Mayo lake control structure replacement preliminary engineering; and
- Mayo generating station water use licence renewal.
"The newest independent review is clear: the spillway is at the end of its life and needs to be replaced. We support fully replacing the spillway because it is the most effective way to reduce the risk of failure. We are also being upfront about the cost. This is a major infrastructure project in a remote northern environment, under tight timelines, with real consequences if it is not replaced soon. The priority now is getting the work underway, reducing risk and making sure this facility can operate safely for the long term. This project is about ensuring safety and energy security for Yukoners."
Minister of Energy, Mines and Resources Ted Laking
