The NWT Power Corporation says its beleaguered Taltson hydro plant will remain out of action until at least early December because of a corrosion problem.
Taltson has now endured years of setbacks. Every week without the plant is another week burning expensive and polluting diesel for South Slave communities, at a time when the power corporation faces huge cost pressures.
The latest issue, first publicized last month, involves corrosion in the surge tank – a component that the power corporation said “regulates pressure fluctuations and provides a water reserve.” When Taltson starts up or shuts down, the surge tank helps the plant to cope with the effects of the associated pressure surges.
“The hydro unit cannot be safely returned to service until the surge tank issue is resolved,” NTPC stated on Thursday afternoon.
“It is expected that the remediation work will take approximately nine weeks to complete, which will then be followed by approximately one week of commissioning of the Taltson unit.
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“This will require South Slave hydro communities to remain on diesel until early December.”
Taltson has existed for 60 years. Since the plant was shut down in May 2023 for what should have been a six-month-long overhaul, it has experienced a series of major problems.
The overhaul ended up taking nearly two years, not helped by a wildfire burning through the site and a series of issues with equipment. The bill for the overhaul soared from $70 million to more than $115 million.
Taltson had only been back for a few months when it was taken offline again for what was billed as summer maintenance. At that point, the corrosion concern became apparent.
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NTPC says inspections by engineers in 2013, 2015 and 2023 did not identify much deterioration, while a “more comprehensive” inspection planned for 2020 did not go ahead “for several reasons.”
“Instead, this test took place in late July 2025 and the results were intended to inform the future capital requirements for the tank. The results of the July 2025 inspection by third-party engineers indicated that the situation was more serious than expected,” the power corporation said on Thursday.
The cost of work to fix the surge tank is estimated at $15 million, including $5.2 million in more diesel fuel for the South Slave.
“The remediation costs are high but the work is necessary to ensure safe operation and bring Taltson back online as quickly as possible,” NTPC president Cory Strang was quoted as saying.
In the longer term, the tank will need replacing, which will be another expensive project. That project is likely to begin “in the next couple of years,” NTPC stated, adding that applying a temporary fix now and coming up with a solid plan for the tank’s eventual replacement is “the lowest-cost option.”
The power corporation said it has added more diesel generation and hired more workers to keep powering South Slave communities while Taltson stays offline. That includes two extra rental generators in Fort Smith and an additional one in Fort Resolution, while two rental generators already in Hay River will remain in service until Taltson returns.
