Hay River, Northwest Territories, September 25, 2025 – The Northwest Territories Power Corporation (NTPC) announced today that it has identified a path forward to remediate the surge tank at the Taltson Hydro site. A corrosion issue in the surge tank has kept Taltson offline since early August as the hydro unit cannot be safely returned to service until the surge tank issue is resolved.
A surge tank is a vital component of a hydroelectric facility that regulates pressure fluctuations and provides a water reserve. It helps to mitigate the effects of pressure surges caused by sudden changes in water flow, especially during startup, shutdown, or load changes, enhancing the overall stability and efficiency of the system.
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. This will require South Slave hydro communities to remain on diesel until early December.
The surge tank was inspected in 2013 by NTPC engineers and in 2015 by a third-party structural engineer. In 2023, the interior condition of the tank was inspected and mapped using a drone. The 2023 drone inspection indicated that the condition of the tank did not show much more deterioration than what was observed in the 2015 inspection.
In 2020, a more comprehensive inspection involving non-destructive testing was scheduled but was cancelled 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.
Although remediation or replacement of the surge tank was not included in the scope of the Taltson Overhaul, it has been recognized as a future need in NTPC’s five-year capital plan. The cost of the remediation work is estimated at approximately $15 million, including approximately $5.2 million in production fuel to power the South Slave while Taltson remains offline.
If this remediation work does not proceed, the South Slave hydro communities would have to remain on diesel generation for the next two years while a new tank is engineered, procured and installed. The fuel and operational costs for this option would likely be in the neighbourhood of $80 million. This remediation project is the first step in a broader, long-term project to replace the surge tank.
A second phase of the project will see complete replacement of the surge tank in the next couple of years. Planning for the second phase has begun and the current concept has a new surge tank being installed upstream of the current tank. The new tank can be built offsite in sections and then transported to the hydro site and welded together. The advantage of this approach is that it can be completed in parallel with the already-scheduled new substation project at Taltson and some costs can be shared. More information about Phase 2 will be provided as planning advances.
The selected approach, with the remediation of the current tank and upstream replacement in a few years, is the lowest cost option. It ensures safe operation, returns the south slave to hydro generation earlier, reduces greenhouse gas emissions and reduces hydro downtime when the second phase of the project runs parallel with the scheduled substation replacement.
NTPC has informed the Public Utilities Board (PUB) that it will be applying for a Project Permit to carry out the remediation work as the PUB requires that all capital projects greater than $5M have an approved permit.
While Taltson remains offline, NTPC is taking steps to enhance reliability in the South Slave such as increasing diesel generation capacity, improving coordination systems, hiring additional employees and completing additional vegetation management.
There will be two additional rental generators in Fort Smith, one of which has already been installed and connected to the local grid. In Hay River, the largest generator returned to service in August following a significant overhaul and two rental units will remain at the local plant until Taltson returns to service. A rental generator was connected earlier this month in Fort Resolution to support reliability.
The additional employees are required to support monitoring and maintenance activities in the communities as well as at the Taltson site to ensure the diesel generators run smoothly while hydro generation is unavailable.
With the extended shutdown, additional vegetation clearing along the transmission right-of-way is being completed in hard-to-reach locations. This will reduce the risk of trees weakened by wildfires and drought conditions from creating faults on the line once Taltson hydro is returned to service and the transmission line is re-energized.
NTPC is a wholly owned subsidiary of NT Hydro, which in turn is 100 percent owned by the Government of the Northwest Territories.
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“Aging infrastructure such as the surge tank at Taltson poses significant challenges to NTPC as well as other Canadian utilities. Given that our North and South Slave hydro grids are not connected, we must rely on diesel generation when Taltson is offline to maintain service to our customers and this is a significant portion of the cost. The remediation costs are high but the work is necessary to ensure safe operation and bring Taltson back online as quickly as possible.”
Cory Strang, President and CEO of the Northwest Territories Power Corporation
Quick Facts
- The Taltson Hydroelectric Facility was constructed in 1965 to support the Pine Point Mine – the surge tank was part of that original construction
- The surge tank includes a 16’ by 54’ riser, an 18.6’ transition and a cylindrical tank of 40’ by 41.7’ with a diameter of 40’
- The surge tank rests on six steel round hollow section columns: The legs rest on concrete pedestals.
For media inquiries, please contact:
Doug Prendergast
Northwest Territories Power Corporation
867-874-5202