The project is likely to cause significant adverse environmental effects, said the country's Minister of Environment and Climate Change and Minister responsible for the Impact Assessment Agency of Canada, Jonathan Wilkinson.
Citing the Canadian Environmental Assessment Act, the government said the project would affect surface water quality, including from selenium effluent discharge, and potentially the Westslope Cutthroat Trout, which islisted as threatened under the Species at Risk Act.
In addition, it would impact the Physical and cultural heritage of the Kainai, Piikani and Siksika First Nations, for example on their Current use of lands and resources for traditional purposes.
"It is in Canada's best interests to safeguard our waterways for healthy fish populations like the Westslope Cutthroat Trout, respect Indigenous peoples' culture and way of life, and protect the environment for future generations," said Wilkinson.
The Grassy Mountain Coal Project, which Benga planned to construct near the Crowsnest Pass, would have had a production capacity of up 4.5 million tonnes of processed coal per year, over a mine-life of about 25 years.
