Methylmercury levels are expected to rise in the reservoir created by construction of the Muskrat Falls hydroelectric project in Labrador, officials with Nalcor Energy confirmed Wednesday, saying local residents can eventually expect an advisory warning them to limit their consumption of fish.
The prediction came soon after the provincial government ordered Crown-owned Nalcor to remove more forest cover from the land that will be flooded to create the 41-square-kilometre reservoir – a process that is expected to begin later this month.
The additional cutting is meant to address the concerns of critics who say the water will be contaminated with unacceptable levels of methylmercury if too many trees are left to rot at the bottom of the reservoir. The neurotoxin is linked to heart issues, intellectual problems in children and other effects.
"For fish in the reservoir, I think we would generally expect levels to rise high enough that we would consider advising people not to eat fish that often," said Gilbert Bennett, executive vice-president of power development.
"We're not saying it's not safe. It's entirely safe to eat. The only question is, taking appropriate steps to mitigate the risk."
The project is upstream from 2,000 Inuit in the Lake Melville region who rely on fish and seal meat.
Bennett said similar advisories have been issued for waters adjacent to other hydroelectric projects in the province, and across Canada and the United States.
"We're in this for the long haul," he said. "We have a long-term common objective to make sure that the health of everybody is protected."
The warning came after a Nalcor official said predictive models have indicated that over a five to 15-year time period, methylmercury levels in the reservoir fish are expected to rise between 2.3 and 4.8 times current levels in the lower Churchill River before falling back to baseline levels.
The impact on people's health would depend on who will be eating the fish, what type of fish they eat, and how often they eat it. Children and women of child-bearing age are the most vulnerable to the detrimental effects of methylmercury, which is formed when inorganic mercury interacts with bacteria typically found in lakes and streams.
Dr. David Allison, the project's chief medical officer, said the predicted increase was comparable to hydroelectric reservoirs in Quebec, which have seen levels increase by three to seven times before falling off over time.
"The process (of methylmercury contamination) is not limited to hydroelectric development," Bennett said. "The process happens, to varying degrees in wetlands, in lakes and rivers. There you'll find mercury in fish that is unrelated to any hydroelectric development."
Removing more trees from the reservoir area would help reduce the amount of methylmercury in the water, but senior biologist Jim McCarthy said removing the soil from the basin would have a much bigger impact.
Bennett said such a move would be unprecedented for a hydro project, though he said Nalcor would look into the feasibility of such a move.
The project in central Labrador is well behind schedule and over budget. Estimated costs have soared to $11.4-billion from $7.4-billion four years ago. First power has been delayed until 2019.
A spillway has been built to divert the lower Churchill River from the site where the dam will be built. Company officials said the reservoir, at 41-square kilometres, will be tiny compared with the existing 2,300-square-kilometre reservoir upriver at the Churchill Falls hydroelectric project.
Bennett said protecting human health has been the subject of numerous studies and the continued monitoring of fish, wildlife, sediment and water at the site for the past 20 years. He also cited studies that have established baseline data based on human hair samples and dietary surveys taken from 300 people in five communities in the area, virtually all of them aboriginal residents.
Earlier this week, plans to start the flooding at the site west of Happy Valley-Goose Bay sparked protests and a number of arrests.
Labrador Liberal MP Yvonne Jones, parliamentary secretary to the minister of indigenous affairs, has said she wants Premier Dwight Ball and Nalcor to hold more talks with local residents before any flooding is done.
Provincial Environment Minister Perry Trimper issued a statement Wednesday saying the province is working with aboriginal governments in Labrador to improve oversight for the project. As well, the province is committed to setting up a new water-quality monitoring program and an independent expert advisory committee.
The province has also told Crown-owned Nalcor Energy that it must pay for a study to be conducted by Dr. Elsie Sunderland at Harvard University in Cambridge, Mass.
"We are taking action that clearly demonstrates our commitment to enhance measures which ensure we are best positioned to protect human health," Trimper said in a statement.