A potentially dangerous situation last spring and concerns about the future have led Hydro-Québec to make major changes to the Bell Falls dam and generating station on Rivière Rouge.
Hydro held a public meeting attended by approximately 50 people on December 3 in Calumet to explain the work that is taking place this winter to increase the flow of water through the dam and power station, in order to reduce the pressure on the structures during future spring floods.
Higher than normal precipitation amounts last winter led to significantly higher water levels on the Rouge last spring. On April 25 when outflows at Bell Falls reached 990 cubic metres per second, Hydro officials became concerned that the water would destroy the dam and station and lead to damage and loss of life downstream. Residents of affected properties were evacuated for a week.
Hydro-Québec Dam and Infrastructure Expert Annick Bigras said the 2019 flows were a one-in-one-thousand years event. On April 1, moisture amounts in the soil due to snowfall were 177 per cent of normal and rainfall was 210 per cent of normal.
According to Hydro-Québec Chief of Projects and Installations Marc-André Lefebvre, the water intakes do not allow a large amount of water to run through it at this time. Hydro will be making modifications to the turbines so that more water can be accommodated. Power is not being generated at the site but the changes to the turbines will be reversible in case Hydro decides to begin generating there again. The control gates and the overhead crane in the powerhouse will require inspection to ensure they can be safely operated after years of disuse. The changes in the powerhouse will allow 90 cubic metres per second to be discharged through the generating units.
To complement the powerhouse work, the utility will be installing new anchor walls at the crest of the dam this winter, removing a concrete wall, and excavating bedrock on the right bank of the river at the dam. With the complementary work and powerhouse changes, 20 per cent more water will be able to flow through Bell Falls.
Hydro-Québec Project Coordinator José Kanou said there is a short schedule to complete the work, especially due to constraints and risks associated with winter construction. However, contractors are already on site and the powerhouse work is to begin in the next two weeks with the goal of having it completed before spring. If the work is completed before spring, the currently disused inflatable device that can add height to the dam when required will also be removed.
Lefebvre said the work at Bell Falls will cost Hydro $3,985,000. Instead of the changes being made to the powerhouse and existing dam, the alternative was to construct a new canal on the left bank or east side of the river for water to pass through.
Communication was the biggest concern audience members shared over what has happened at Bell Falls since last spring. One resident expressed regret that more information and representation from Hydro-Québec had not been available during the initial emergency. Hydro-Québec Milieu Relations Counsellor Sophie Lamoureux acknowledged the need to be more proactive and said Hydro will provide updates on the progress of the construction work to the municipality of Grenville-Sur-La-Rouge which it will add to its website along with links to other information about emergency preparedness and response.
Lamoureux said the April emergency was a first for hydro and the utility had to act fast to notify the Ministère de sécurité publique (MSP) and Sûreté du Québec (SQ) of the imminent danger. The MSP and SQ then notified the municipality.
Cell phone text messages were suggested as one way of keeping residents better informed, but several residents noted that mobile phone service in the area is poor to non-existent.
“I am pleased they are fixing it and doing work on the dam,” said Ann Maclean-Wiersma of Cornwall, who owns a vacation property downstream of Bell Falls. She is confident the work being done will diminish the potential for future flood emergencies.