Quebec targets hydro plant’s dissolved gas for fish death events

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The Quebec Ministry of the Environment has accused a Masson-Angers based hydroelectric plant of being responsible for a series of fish deaths in the Lièvre and Ottawa rivers over what it’s calling a “supersaturation” of dissolved gas.

Quebec first became aware of the fish kills in early July, after the dead aquatic wildlife turned up downstream of Lièvre Power LP and Energy Services Brookfield Inc. Weeks later, the presence of 100 fish corpses were reported in the Masson-Angers ferry sector on the Ottawa River, according to the Ministry of Forests, Wildlife and Parks. In early August, dead fish surfaced yet again after a number of similar reports.

According to Ottawa River Keeper: “It is now clear that thousands of fish have been killed over the course of these incidents, though it is impossible to get an exact figure.”

There were several accounts given to the Ministry of Environment describing “whitish and brown foam” present on the Ottawa River near the structure overflow from the wastewater treatment plant. The river seemed to contain a lot of gas since it produces a noise of degassing, witnesses told the province.

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On August 2, representatives from the Ministry of the Environment and the Fight against Climate Change installed a probe to analyze the physicochemical parameters of water at the coastline of the Hare River, but found no abnormalities. Later, research demonstrated that the phenomenon of the supersaturation of the water in dissolved gas can occur by the suction of air at the water inlet of a hydroelectric plant, which may be caused by debris build-up and cleaning work at the Masson-Angers plant.

Provincial researchers explained that supersaturation in dissolved gas can cause the formation of a plume and accumulation of foam on the surface of the water and a degassing noise.

Some of the dead fish were found with gas bubbles in their tissues, provincial officials explained.

After its investigation, the province announced on August 15 that Lièvre Power LP and Energy Services Brookfield Inc. must comply with a number of requests under the Environment Quality Act to ensure any further impacts on fish life are limited.

“[…] I deem it imperative to send a clear message to its leaders that their activities must be carried out with respect for the environment and, in this case, for aquatic life,” announced Benoit Charette, Minister of the Environment and the Fight against Climate Change. “I use the recourses available to me to do my best to return to normal in Gatineau,” he added.

The province has ordered the hydro plant to limit the risk of supersaturation of dissolved gas in the water discharged at the outlet of the plant in the Lièvre River. Plant staff must ensure close monitoring of the situation at all times, and in the short term continuously measure the rate of supersaturation in dissolved gas with specialized equipment. The plant’s owners must also notify the Quebec Ministry of the Environment of any level of dissolved gas saturation exceeding a threshold considered critical for aquatic life.

Evolugen, the new name for Brookfield Renewable Canada, told CBC News that the need for more cleaning around the hydro facility was due to spring flooding that caused unusually high levels of debris in the Lièvre River.

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