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Site C dam impact

The province of Alberta is concerned that a multibillion-dollar hydroelectric dam proposed in northeastern British Columbia could increase mercury levels in fish and escalate the risk of floods or drought along the Peace River that flows through its province.

Alberta's Environment and Sustainable Resource Development, which manages lands, forests, fish and wildlife in the province, has filed a 23-page submission setting out its concerns to the panel reviewing the massive project.

Environmental review hearings for the $7.9-billion Site C dam proposal by BC Hydro are underway in Fort St. John.

Two existing dams on the Peace River in BC have already significantly altered the flow of the river into the neighbouring province, the Alberta submission said, and this has both positive and negative impacts in Alberta.

"Alberta is concerned that Site C will further exacerbate the negative impacts," said the document filed Nov. 29.

The Site C dam would flood an 83-kilometre stretch of the Peace River from approximately Fort St. John to just upstream of Hudson's Hope. It would be the third dam on the river, downstream from the W.A.C. Bennett and Peace Canyon dams.

The two existing dams already lower the river's natural flow from May to late July, and increase flow from mid-October to mid-April. There are benefits to the flow regulation from BC Hydro, such as a reduced risk of flooding, but there are also risks, Alberta said.

Among those risks is an expected increase in methylmercury levels in fish during construction of the dam.

"Alberta acknowledges that BC Hydro expects increases in MeHg levels in fish populations downstream of the Alberta-B.C. border to be temporary and within fish consumption guidelines," the submission said.

"However, it is unclear whether Albertans are aware of this increase, the amount of the increase, and the duration of the impact."

The Alberta government requested ongoing information from BC Hydro to enable the province to inform fishermen on the Peace River of changes to methylmercury levels in fish until concentrations return to pre-construction levels.

The impact of the dam on managing ice-related flooding and concern about minimum flow rates during construction were also singled out as concerns. Reduced peak flow affects the aquatic ecosystem on the Peace River, the Peace-Athabaska delta and other riparian wetlands, the document said.

Water fluctuations also cause mortality to fish and eggs by stranding, or indirectly through increased stress on fish, the report said.

There are also concerns about changes Site C will cause in water temperature downstream from the dam and reservoir, making the Peace River slower to warm in spring and slower to cool in summer.

"Such changes to water temperatures, though slight, may impact the current distribution and range of cold and cool water fish species within Alberta causing potential declines in some species and increases in others," the report said. "Temperature changes may also impact the timing of ice freeze-up and break-up events."

That could result in changes to spawning runs, in egg incubation rates and access to spawning habitat, the submission stated.

The province is also concerned about the flow of fish in the river.

"Upstream and downstream movement of fish populations is necessary for gene flow and hence long term resiliency in those populations, as well as to allow access to spawning, rearing, feeding, and overwintering areas," the report said.

BC Hydro has told the neighbouring province that it is exploring options for fish passage, but as yet, "Site C could result in more restrictive fishing opportunities for species Albertans value more highly in the Peace River."

The Canadian Press

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