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Headworks and surge tower upgrade (tunnel project)

What we're planning

We’re working to upgrade the tunnel between Alouette Lake Reservoir and Stave Lake Reservoir to ensure the infrastructure can withstand and remain operable following a major (one in 10,000-year) earthquake. We’ve updated our Dam Safety Plan to address potential issues that may arise if a major earthquake occurs before the tunnel upgrade project is complete.

To make these upgrades, we’ll be required to drain the tunnel and remove it from service while construction is underway. This will result in the need to temporarily alter how we manage operations and inflows to Alouette Lake Reservoir for two to three years (depending on construction progress) potentially starting in 2023.

Reservoir management: three options

We have identified three potential reservoir management options, all of which require a variance from the Comptroller of Water Rights. The descriptions that follow highlight changes required from our normal operations.

Options:

This option would not require the reservoir to be lowered during the summer months. It does keep the tunnel closed between June 15 and December 31 whereas it would be open part of this time during normal operations. The water that would typically pass through the tunnel when Alouette Lake Reservoir is above 122.6 metres would be passed to the South Alouette River, resulting in flows of up to 43 metres3/s compared to the  3 metres3/s for fish flows during normal operations between June 15 and December 31.

This option requires a change to operations at  Alouette Lake Reservoir and closing the tunnel between it and Stave Lake reservoir from July 15 to October 31. The reservoir would be lowered to 116 metres between June 15 and September 15. During normal operations, the minimum reservoir elevation during this time ranges from 121.25 metres to 122.5 metres to support recreational use of the reservoir. With this option there would be no change to the amount of water passed to the South Alouette River, fish flows would remain at  3 metre3/s of water during normal operations.

This option is similar to option 2 and would involve lowering Alouette Lake Reservoir to 118 metres (compared to 116 metres in option 2) between June 15 and September 15. The tunnel between Alouette Lake and Stave Lake reservoirs would be closed from July 1 to October 31. With this option, up to 7 metre3/s of water would be going down the South Alouette River.

Next steps: consultation and evaluation

Thanks to those that attended our virtual information session earlier this year. See the presentation slides [PDF, 2.34 MB].

We’re seeking feedback from Indigenous Nations and stakeholders on these options and will use this feedback, while also taking into account archaeological, environmental, operational, schedule and cost considerations to make a decision on a reservoir management option for construction.